Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices

Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices Jin-Mun Yun, Soyeon Si, Dami Yun, Youn-Mook Lim, Hyun Bin Kim, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8276245/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Radiation-induced reduction is used to synthesize nanoparticles owing to its strong reducing power. However, reduced metal atoms readily aggregate because of their enhanced mobility, localized heating, and precursor migration during synthesis. Consequently, achieving single-atom dispersion remains challenging, highlighting the need for a reaction environment that suppresses diffusion and heat-induced aggregation during irradiation. Here, we present a new radiation-induced synthesis strategy that effectively controls precursor migration and aggregation by employing a frozen-state environment. This approach enables the formation of a radiation-induced single-atom catalyst (RI-SAC) in which Pt precursors are atomically dispersed on the support surface. The resulting RI-SAC exhibits excellent activity toward both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), with a turnover frequency (TOF) and mass activity of up to 3.6 and approximately 8 times higher than those of commercial Pt/C, respectively. Moreover, the process is scalable, continuous, and capable of producing approximately 313 g of catalyst per tray at 1 min intervals, corresponding to a daily yield of nearly 446 kg. Therefore, this synthesis approach provides a versatile and industrially viable platform for the large-scale production of single-atom catalysts (SACs) based on various metals, such as Pd and Ir. Physical sciences/Materials science/Materials for energy and catalysis/Electrocatalysis Physical sciences/Chemistry/Catalysis/Catalyst synthesis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Single-atom catalysts (SACs) have emerged as an effective strategy to maximize the utilization of precious metals in catalytic reactions. Catalytic reactions generally occur on the catalyst surface, thereby leaving bulk-embedded atoms largely inaccessible 1 , 2 . Consequently, achieving nearly 100% dispersion on the surface of SACs is crucial for enhancing catalytic activity. SACs contain isolated metal atoms that behave as individual active sites during electrochemical catalysis. This atomic configuration restricts the adsorption modes of reactants, thereby improving reaction selectivity 3 , 4 . A representative example of such enhanced selectivity is the two-electron oxygen reduction reaction (2e − ORR) that produces H 2 O 2 5, 6 . However, the isolated metal atoms in SACs are thermodynamically unstable and tend to aggregate during synthesis or under reaction conditions to reduce the total free energy. Individual atoms may also detach from the support under reaction conditions 7 , 8 . The effective utilization of single atoms as active sites may be achieved by (1) ensuring the uniform dispersion of single atoms and (2) firmly anchoring them onto the support, both of which are key to the synthesis and practical application of SACs. In particular, uniform dispersion and strong metal–support anchoring are essential to suppress atomic migration and nanoparticle formation during precursor reduction. At present, the scalable synthesis of catalysts that meet these conditions remains a considerable challenge. Synthesis strategies for SACs incorporating the key factors mentioned above have been extensively developed in recent years. For instance, atomic layer deposition exploits self-limiting surface reactions to enable atomic-scale growth with submonolayer precision 9 – 14 . Wet impregnation, followed by drying and thermal activation, can anchor isolated metal atoms through precursor–support interactions 15 – 22 . Sputtering-based physical vapor deposition, a top-down synthesis strategy, provides a feasible route to produce SACs, as the plasma intensity applied to the target metal can be finely tuned to eject single atoms and deposit them at the atomic scale onto a support 23 – 25 . Integrated strategies have also been devised to enable both the high dispersion and strong anchoring of single atoms. In such strategies, metal ions are uniformly embedded within precursors such as polymers, small molecules, metal–organic frameworks, or organometallic complexes, and subsequent pyrolysis under controlled atmospheres yields atomically dispersed catalysts 26 – 30 . Recent reports have demonstrated the feasibility of the kilogram-scale production of SACs through mechanochemical approaches. For instance, ball milling, a typical mechanochemical method, employs impact and shear forces generated between colliding particles to drive solid-state reactions 27 , 31 – 34 . Such methods typically rely on batch-to-batch systems, thereby posing challenges to continuous synthesis and reducing process efficiency. Production capacity is also restricted by the reactor size and throughput, as scaling up requires multiple units, creating spatial and economic limitations. Scale-up also introduces additional challenges such as high-temperature operation, complex post-treatment, particle aggregation, poor uniformity control, and metal contamination. Therefore, alternative and more practical approaches should be developed to enable the scalable production of SACs without compromising their atomic dispersion. To bridge this gap in the literature and address the limitations of current techniques, we propose a new approach that employs the radiolytic reduction of metal ions to synthesize SACs. Upon irradiation, water is radiolyzed, generating hydrated electrons (e aq ⁻) and hydrogen radicals (H·), which act as strong reducing species that convert metal precursors into their metallic state. This process does not require chemical reductants or stabilizers, enabling high-purity catalyst synthesis. It also offers straightforward process control that is well suited for mass production when integrated with a continuous electron-accelerator conveyor system. It can also induce uniform and rapid reduction reactions throughout the entire reaction volume. Leveraging these advantages, irradiation with electron beams (e-beams) or gamma rays has been widely explored for Pt nanoparticle synthesis; however, the reduced Pt atoms readily migrate and aggregate into nanoparticles, demonstrating limited control at the single-atom level. To overcome this issue, we irradiated a frozen Pt precursor solution with e-beams, effectively suppressing atomic diffusion while maintaining the reduction reaction environment. In other words, preventing reduced Pt atoms from aggregating or growing into Pt x (x ≥ 2) clusters serves as the core strategy of our e-beam-based SAC synthesis. We confirmed that Pt atoms were stabilized in the single-atom form without growing into nanoparticles, and demonstrated that the mass production of Pt single atoms (Pt 1 ) is possible using an electron-accelerator conveyor system. Furthermore, the e-beam-reduction mechanism can also be applied to various metal precursors such as Pd and Ir, demonstrating that this approach can be extended to a universal SAC synthesis platform. Using this system, we successfully developed a radiation-induced SAC (RI-SAC). RI-SAC exhibited enhanced catalytic performance compared with commercial Pt/C in both the hydrogen evolution reaction (HER) and the 2e − ORR, which are the key processes in water electrolysis and H 2 O 2 production, respectively. Notably, RI-SAC demonstrated remarkable scalability for mass production. The e-beam conveyor system enabled the continuous fabrication of approximately 446 kg of catalyst per day. This work is the first to report a significant advance in SAC synthesis and to demonstrate a production capacity suitable for industrial-scale demand. By satisfying the key requirements of SACs, including high atomic dispersion, strong metal–support interactions, and large-scale producibility, RI-SAC provides a robust and scalable platform for the advancement of the catalyst industry. Results Figure 1 presents a stepwise overview of how Pt₁ can be generated within a Pt-precursor/carbon/water mixture frozen at − 30°C (hereafter referred to as the frozen hybrid matrix) under e-beam irradiation, integrating both macroscopic and microscopic perspectives. Figure 1 a illustrates the macroscopic sequence in which radiolytically generated reducing species (e aq ⁻ and H·) locally reduce Pt precursors within the immobilized frozen hybrid matrix 35 – 38 , followed by anchoring of the resulting Pt₁ species onto carbon or nitrogen-doped sites during thawing. The frozen hybrid matrix effectively restricts long-range molecular mobility of Pt atoms and Pt precursors, thereby suppressing aggregation pathways that require translational accessibility 39 , 40 . Figure 1 b expands this structural concept to the microscopic scale. During ice-crystal growth, micro-brine pockets form as solutes are excluded from advancing ice fronts 41 , 42 . and carbon particles are displaced toward these solute-rich liquid domains where they may reside at or within the brine-pocket regions 43 . Consequently, the Pt precursor becomes relatively enriched within the micro-brine pockets—and in the ultrathin interfacial water layers surrounding carbon surfaces—while its concentration within the pure-ice lattice remains minimal due to the strong exclusion of ionic species 44 – 50 . This spatial segregation, together with the markedly reduced long-range mobility of Pt-containing species imposed by the frozen matrix, creates conditions in which reduced Pt atoms rarely encounter one another, thereby lowering the likelihood of cluster formation. Figure 1 c illustrates the reduction pathways within the frozen hybrid matrix across three micro-domains—pure ice, micro-brine pockets, and carbon-adjacent regions. E-beam irradiation generates track structures composed of spurs that produce radiolytic reducing species such as e aq ⁻ and H· 51 . Carbon particles additionally emit low-energy secondary electrons or backscattered electrons (emitted electrons) 52 – 55 . These electrons directly reduce Pt precursors that accumulate at the carbon–ice interface because of their close proximity to the emitting surfaces. In contrast, radiolytic species, although exhibiting limited mobility at cryogenic temperatures, can still diffuse over several nanometers within spur regions or interfacial quasi-liquid layers (QLLs) 56 , 57 , enabling reduction of Pt precursors located in micro-brine pockets as well as in carbon-adjacent regions, where precursor concentrations are comparatively higher. Taken together, the distribution of precursors within micro-brine pockets, the spatially confined production and short-range transport of reducing species originating from spurs and tracks, the supplementary contribution of emitted electrons near carbon surfaces, and the overall suppression of mobility under frozen conditions collectively act to reduce the likelihood of aggregation of reduced Pt species. These combined factors suggest that e-beam irradiation under frozen-state conditions can provide a physicochemically favorable environment for the formation and stabilization of Pt single atoms. Building on this mechanistic basis, we applied frozen-state e-beam irradiation to the frozen hybrid matrix to synthesize isolated Pt species on the N-doped carbon support, the detailed analysis of which is presented in Fig. 2 . To elucidate the structural and chemical characteristics of the synthesized catalyst, we conducted conventional physicochemical characterizations. Quantitative analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) revealed that RI-SAC contains approximately 1.87 wt% Pt, further confirming the successful incorporation of atomically dispersed Pt species. The atomic dispersion of Pt in RI-SAC was verified by X-ray diffraction (XRD) (Fig. 2 a). The two broad peaks at approximately 25° and 43° (2θ) correspond to the (002) and combined (100)/(101) planes of graphitic carbon, respectively 58 . Although the sharp metallic Pt peaks of commercial Pt/C were detected, RI-SAC showed no distinct Pt reflections, indicating the presence of atomically dispersed Pt rather than clustered or particulate forms. High-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM) provided direct visual evidence of the single-atom dispersion of Pt (Fig. 2 b). Bright atomic-scale spots were homogeneously distributed over the carbon region, consistent with the presence of isolated Pt atoms. Elemental mapping by energy-dispersive X-ray spectroscopy (EDS) confirmed that these bright features correspond to Pt single atoms (Fig. 2 c), while the presence of nitrogen signals indicated successful N-doping of the carbon framework. The chemical state of Pt was then examined by X-ray photoelectron spectroscopy (XPS) (Fig. 2 d). Pt/C exhibited a prominent metallic Pt 0 signal in the Pt 4f region, whereas RI-SAC showed no detectable Pt 0 component, suggesting that Pt exists predominantly in an oxidized form. To obtain an in-depth understanding of the interfacial interaction between atomically dispersed Pt sites and nitrogen functionalities within the carbon support, we compared the N 1s XPS profiles of RI-SAC and N-doped carbon (Supplementary Fig. 1). The exclusive appearance of a new peak at ~ 400.1 eV in the N 1s XPS profile of RI-SAC indicates nitrogen incorporation and the formation of N x –Pt coordination bonds, reflecting strong Pt–N interactions. To investigate the electronic structure and coordination state of Pt, we performed Pt L 3 -edge X-ray absorption spectroscopy (XAS). The X-ray absorption near-edge structure (XANES) spectra revealed that the white-line intensity of RI-SAC was located between those of Pt foil and PtO 2 (Fig. 2 e), indicating partially oxidized Pt species with an intermediate valence between 0 and + 4. This finding is in excellent agreement with the XPS results. Extended X-ray absorption fine structure (EXAFS) analysis revealed no Pt–Pt coordination peak typically observed for metallic Pt, confirming the atomically isolated nature of Pt in RI-SAC (Fig. 2 f). These results collectively establish that Pt is atomically anchored on the N-doped carbon support in an oxidized single-atom configuration. The XAS results are consistent with the structural features revealed by XRD and TEM. Given the pivotal role of the HER in water electrolysis, the catalytic performance of RI-SAC was evaluated to assess its intrinsic activity for this reaction. As shown in Fig. 3 a, RI-SAC exhibited a higher overpotential than commercial Pt/C at 10 mA cm − 2 , reflecting its lower HER activity. This result is reasonable because the Pt loading of RI-SAC (≈ 6.12 µg Pt cm − 2 ) is approximately 10.7 times lower than that of Pt/C, which contains ≈ 65.4 µg Pt cm − 2 (Supplementary Fig. 3). The distinct mechanistic nature of single-atom catalysis also accounts for this difference. In nanoparticle catalysts, adjacent active sites allow both Volmer–Tafel and Volmer–Heyrovsky pathways, enabling efficient electron transfer and H–H bond formation. By contrast, SACs possess isolated metal centers that render the Tafel step impossible, predominantly following the Volmer–Heyrovsky route 59 . Such mechanistic constraints inevitably lead to higher overpotentials and slower hydrogen evolution kinetics. Therefore, a comparative evaluation of SACs and nanoparticle catalysts in terms of Tafel slope and turnover frequency (TOF) is crucial to understand their reaction kinetics and intrinsic site activity. The combined analysis of these parameters provides quantitative insights into the inherent activity and kinetic behavior of each catalyst. As shown in Fig. 3 b, the two catalysts exhibit nearly identical Tafel slopes, suggesting that charge transfer in RI-SAC occurs efficiently despite its mechanistic constraints. Comparison of the TOFs calculated at six overpotentials (50–300 mV RHE , Fig. 3 c) revealed that the TOFs of RI-SAC are 3.15–3.6 times higher than those of Pt/C (7.63 s − 1 at 100 mV RHE , 42.0 s − 1 at 300 mV RHE ). On average, the TOF of RI-SAC is enhanced by approximately 3.3-fold compared with that of Pt/C across the overpotential range investigated. The TOF performance of RI-SAC demonstrates that each of its active sites has higher intrinsic reactivity than those of Pt/C, which can be attributed to the superior atom utilization efficiency of its single-atom architecture. These results indicate that the catalyst not only features atomically uniform dispersion but also high activity at individual atomic sites. This enhanced intrinsic activity likely originates from the strong coordination between isolated Pt atoms and the N-doped carbon support, forming stable M–N x moieties that optimize the electronic structure for the alkaline HER. To evaluate the durability of RI-SAC, we conducted chronopotentiometry (CP) measurements for 10 h. As shown in Fig. 3 d, RI-SAC maintains a stable current response throughout its long-term operation. According to the CP results, the performance retention of RI-SAC (Fig. 3 e), at 73.3%, is higher than that of Pt/C (60.9%), indicating a smaller increase in overpotential during long-term electrolysis. After the CP test, the HER polarization linear sweep voltammetry (LSV) curve (Fig. 3 f) was re-evaluated. Pt/C exhibited noticeable performance degradation, whereas RI-SAC maintained and even showed a slight improvement in its HER activity. This enhancement is attributed to the partial aggregation of isolated Pt atoms into small clusters during operation, which transiently activates both the Volmer–Tafel and Volmer–Heyrovsky pathways, thereby improving the overall reaction efficiency. To investigate the effect of Pt loading amount on the catalytic performance, we conducted additional electrochemical measurements under the same Pt loading conditions (Supplementary Figs. 4–6), considering the substantial difference in Pt content between RI-SAC and Pt/C. Under these normalized conditions, RI-SAC consistently exhibited superior HER performance across all metrics examined. Notably, commercial Pt/C with a reduced Pt loading (1.87 wt% Pt, hereafter denoted as Pt/C(1.87)) demonstrated pronounced performance decay, retaining only 50.4% of its initial activity after 10 h of CP. By contrast, RI-SAC exhibited remarkable stability and sustained catalytic efficiency, unambiguously demonstrating its intrinsic durability advantage over conventional Pt catalysts at comparable metal loadings. To further highlight the outstanding catalytic attributes of RI-SAC, we benchmarked its TOF against those of recently reported HER catalysts. As illustrated in Fig. 3 g, compared with other catalysts, RI-SAC delivers a substantially higher TOF value at an overpotential of 100 mV RHE , underscoring its exceptional intrinsic reactivity and efficient atomic utilization. Owing to the geometric configuration of the single-atom Pt sites, molecular O 2 can only adsorb onto the catalyst on an end-on (Pauling) fashion, which favors the associative pathway for H 2 O 2 generation 60 . To investigate how RI-SAC leverages this geometric feature to selectively drive the 2e − ORR, we conducted comprehensive electrochemical measurements. RI-SAC exhibited a half-wave potential of 0.90 V RHE , as shown in Fig. 4 a, which is slightly lower than that of commercial Pt/C (0.95 V RHE ), indicating its lower ORR activity. Such a result is reasonable and can be attributed to the absolute difference in Pt loading, as mentioned earlier. To compensate for differences in loading amount, we normalized the catalytic performance of the catalysts to their Pt loading, and consequently mass activity was used as a reliable metric to evaluate the intrinsic catalytic performance of both materials (Fig. 4 b). At 0.85 V RHE , RI-SAC achieved a mass activity of approximately 7.0 A mg Pt −1 , whereas Pt/C delivered a mass activity of approximately 0.8 A mg Pt −1 , indicating that RI-SAC is about 8 times more active than Pt/C on a mass basis. To validate its electrochemical superiority, we benchmarked the mass activity of RI-SAC against those of recently reported catalysts. Figure 4 c shows that RI-SAC delivers the highest mass activity among recently reported ORR catalysts. The selectivity of RI-SAC toward the 2e − ORR was investigated by measuring its limiting current density at five rotation speeds ranging from 400 to 2,000 rpm (Supplementary Fig. 7). The resulting Koutecký–Levich (K–L) plots are shown in Fig. 4 d. From the K–L analysis, the electron transfer number (n) was determined to be approximately 2.3 within the potential range of 0.6–0.8 V RHE , where the ORR predominantly occurs (Fig. 4 e). This finding confirms that RI-SAC primarily follows a 2e − pathway, enabling highly selective H 2 O 2 formation. Overall, RI-SAC displays well-balanced performance across both activity and selectivity, rendering it a promising catalyst for cost-effective and high-purity H 2 O 2 production with applicability to semiconductor, environmental, and energy-conversion technologies. To assess the feasibility of the large-scale synthesis of Pt SACs using a 10 MeV electron accelerator, we systematically investigated the dose uniformity of the irradiation process and its applicability to continuous production (Figs. 5 a–e). All experiments were conducted at a target dose of 50 kGy, which is identical to the optimized condition used for small-scale Pt SAC synthesis. Figure 5 a shows the experimental configuration for 3D dose mapping within a single tray (80 × 60 × 10 cm 3 ), with B3000 radiochromic dosimetry films placed at 27 positions in a 3 × 3 × 3 grid along the x-, y-, and z-axes. This configuration enabled the quantitative assessment of the absorbed dose distribution and analysis of electron penetration and attenuation behavior during irradiation. Figure 5 b presents the results of the lateral and traveling dose uniformity measurements. Lateral dose uniformity, which indicates dose flatness across the beam extraction width, exhibited a mean absorbed dose of 49.94 ± 0.47 kGy (≈ 0.94%), with a ~ 1.5 m flat-top region fully encompassing the tray width, confirming highly uniform surface irradiation. Traveling dose uniformity, which was evaluated along the conveyor direction to determine inter-tray consistency, showed a mean of 100.22%, standard deviation of 1.04%, and range of 98.4–102.6% (within ± 2%). These results demonstrate that uniform irradiation is maintained even under continuous multi-tray operation. Overall, the excellent agreement between the beam scanning frequency and conveyor speed ensured highly stable and reproducible irradiation conditions suitable for industrial-scale processing 61 . Figure 5 c presents the 3D dose distribution obtained from the grid defined in Fig. 5 a. The mean absorbed dose was 47.60 ± 1.66 kGy, with a maximum dose of 51.1 kGy (middle-layer center) and a minimum dose of 45.1 kGy (bottom-layer right corner). The dose uniformity ratio (DUR) was 1.133, with a coefficient of variation of 3.5% and standard deviation of 1.66 kGy. These values are below the recommended limit of 1.30 for radiation processing and exceed the ISO 11137-1:2025 criterion (1.25) 62 , indicating superior dose homogeneity throughout the irradiated volume. The spatial dose variations in Fig. 5 c are consistent with the characteristic percentage depth dose profile of a 10 MeV e-beam. Reductions in surface dose arise from a build-up deficiency before the maximum dose depth (d max ), where electronic equilibrium is achieved by forward-scattered electrons, is reached. Beyond d max (~ 2 cm), dose attenuation occurs 63 . In the bottom layer, central dose enhancement is attributed to backscattered electrons from the Al tray, whereas dose reduction at the edges is caused by lateral electron loss and roll-off effects. The central region exhibits a relatively higher absorbed dose owing to forward electron scattering and energy deposition concentration 63 – 65 . These distributions are governed by the electron incidence angle, tray material, and scattering dynamics, demonstrating both the physical consistency and precise dose control of the process. Figure 5 d summarizes the results of a scaled-down, multitray validation experiment performed under full-scale conditions (50 kGy, 1 min intertray interval). Four trays produced a total of 1,253 g of Pt SACs (~ 313 g per tray), confirming uniform synthesis efficiency across trays. The first tray required 16 min from entry to exit (including irradiation and transit), after which one tray containing ~ 313 g of catalyst was continuously delivered every minute. These findings verify the feasibility of high-throughput, continuous operation under stable irradiation parameters. Figure 5 e presents the estimated production capacity of the proposed system under the validated operational conditions. Application of the same process parameters yielded predicted production rates of ~ 14.1 kg h − 1 , ~ 446.38 kg day − 1 , ~ 13.53 ton month − 1 , and ~ 164.6 ton year − 1 , corresponding to an over-400-fold increase compared with previously reported large-scale SAC synthesis methods, which achieve production capacities in the order of 1 kg day − 1 27, 66 . These results confirm that the e-beam-driven synthesis approach developed in this work provides a highly efficient and scalable platform for the industrial-scale production of Pt SACs. Discussion In this work, we successfully synthesized a Pt SAC (RI-SAC) through a radiation-induced strategy conducted in a frozen-state environment. During e-beam irradiation, the generated e aq − and H· reduced the PtCl 6 2− precursor to metallic Pt 0 , thereby achieving the atomic-level dispersion of Pt atoms. In addition, local aggregation that could occur during irradiation was effectively suppressed by the frozen environment and the anchoring effect of nitrogen dopants. The synthesized RI-SAC exhibited outstanding catalytic activity toward both the HER and ORR in an alkaline electrolyte. For the HER, the TOF of RI-SAC was up to 3.6 times higher than that of commercial Pt/C, and the catalyst demonstrated 73.3% performance retention after a 10 h CP test at 10 mA cm − 2 . For the ORR, the mass activity of RI-SAC was approximately 8 times greater than that of Pt/C, and the catalyst followed a distinct 2e − reaction pathway, confirming that the intrinsic single-atom reaction mechanism was preserved. In terms of scalability, the proposed conveyor-based synthesis process can continuously produce approximately 446.38 kg day − 1 (equivalent to ~ 164.6 ton year − 1 ) of catalyst, corresponding to an over-400-fold increase in production efficiency compared with previously reported large-scale SAC synthesis methods, which typically produce the desired materials in the order of 1 kg day − 1 . Therefore, the synthesis method presented in this work offers a highly scalable next-generation platform that is applicable to various SACs, including Pd and Ir, and is expected to contribute broadly to the industrial-scale implementation and development of high-efficiency electrocatalysts (Supplementary Fig. 9). Methods Materials All reagents were used without separate purification. Chloroplatinic acid hexahydrate (H 2 PtCl 6 ·6H 2 O, 8 wt% in water) and potassium hydroxide (KOH, 90%) were purchased from Sigma-Aldrich. Vulcan XC-72 carbon was purchased from Cabot Corporation. Potassium chloride (KCl, EP, 99.9%), ethyl alcohol (anhydrous, GR, 99.9%) and isopropyl alcohol (IPA, EP, 99.5%) were purchased from DAEJUNG Chemicals&Metals Co., Ltd. 5% Nafion™ Dispersion Solution (DE520 CS type) was purchased from FUJIFILM Wako Pure Chemical Corporation. Deionized (DI) water with a resistivity of 18.2 MΩ cm − 1 was produced using the Millipore Direct-Q 3 system. Catalyst synthesis N-doped carbon (N-doped Vulcan XC-72) was first prepared by heat-treating Vulcan XC-72 under a 99.9999% NH₃ atmosphere. For the small-scale synthesis of Pt SACs supported on N-doped carbon (RI-SAC), 0.6 g of the N-doped Vulcan XC-72 was dispersed in DI water, and an aqueous H₂PtCl₆·6H₂O precursor solution was added to give a total volume of 30 mL and a Pt precursor concentration of 5.4 mM. The suspension was purged with N 2 for 15 min to remove any dissolved oxygen and subsequently ultrasonicated for 15 min to ensure the homogeneous dispersion of the carbon support. The resulting dispersion was frozen using a laboratory freezer set to − 30°C. The frozen sample was then loaded onto an Al tray (dimensions: 60 × 80 × 8 cm 3 ) and irradiated using a 10 MeV electron accelerator (MB10-30/3000; Mevex Corp., Canada; maximum beam current: 3 mA; maximum power: 30 kW). The total irradiation dose was fixed at 50 kGy, a condition that maintains the frozen state throughout e-beam treatment. After e-beam irradiation, the resulting sample was recovered by centrifugation at 3000 rpm for 5 min. To remove unreacted precursor species, the product was re-dispersed and centrifuged twice with DI water, followed by an additional washing step with IPA. The final RI-SAC was obtained by drying the material overnight at 80°C. For the large-scale production, the total reaction volume was increased to 15.5 L while maintaining the same precursor ratio, irradiation dose, and purification procedures as in the small-scale synthesis to ensure consistent synthesis conditions. Absorbed dose measurement The dependence of the irradiation dose on the under-beam conveyor (UBC) speed in the 10 MeV electron accelerator was measured using a calorimeter (GeV Corp., South Korea). Specifically, the irradiation dose was measured at various UBC speeds, and the relationship between the reciprocal of the UBC speed and irradiation dose was analyzed through linear regression (Supplementary Fig. 10a). According to our facility’s calibration standard, the measured data were considered valid when the coefficient of determination (R²) exceeded 0.9990. The high correlation (R² = 0.9998) obtained in this study confirmed the reliability of the measurements. Finally, the regression function was used to estimate the irradiation dose as a function of UBC speed (Supplementary Fig. 10b). For instance, a UBC speed of 0.251 m min − 1 corresponded to an irradiation dose of 50 kGy. Dose mapping and evaluation Dose mapping and lateral and traveling dose uniformity evaluation were performed using B3000 and CTA dosimetry films, respectively. The irradiation dose was fixed at 50 kGy, consistent with the optimal condition derived from the simulation. After irradiation, the absorbed dose of the B3000 film was evaluated using a Genesys 20 UV–Vis spectrophotometer (Thermo Fisher Scientific, USA), while the CTA film was analyzed using a Dos’ASAP reader (Freiberg Instruments GmbH, Germany). Physical characterization ICP-OES was performed using a Thermo Scientific iCAP 6000 Series instrument operated with Ar plasma in axially viewed mode. XRD patterns were recorded on a Bruker D8 Focus diffractometer over the 2θ range of 10°–90° with a scan speed of 5° min − 1 . TEM was conducted on an FEI Titan™ 80–300 microscope operated in HAADF mode with EDS. The catalyst powders were dispersed in ethyl alcohol, drop-cast onto a holey carbon film (200-mesh Ni grid), and dried under ambient conditions. XPS measurements were performed using a Thermo Scientific K-Alpha spectrometer equipped with a monochromated Al Kα source (1,486.6 eV). The analysis was carried out under an ultrahigh vacuum below 1 × 10 − 8 mbar with an X-ray spot size of approximately 400 µm. Survey and high-resolution spectra (C 1s, N 1s, and Pt 4f) were recorded, and all binding energies were calibrated with respect to the C 1s peak at 284.8 eV. Data acquisition and peak fitting were performed using the Avantage software package. XAS, including XANES and EXAFS, at the Pt L 3 -edge was conducted at the KIST-PAL beamline 1D (EXAFS) of the Pohang Accelerator Laboratory (PLS-II, Korea) in fluorescence mode, with energy calibration using a Pt foil at the absorption edge inflection point. And acquired data was processed and fitted using the Athena software package. Electrochemical measurements Electrochemical measurements were carried out using an Autolab PGSTAT204 potentiostat with a conventional three-electrode configuration. A glassy carbon disk electrode (geometric area: 0.196 cm 2 ) mounted on a rotating disk electrode setup was employed as the working electrode. A Pt sheet (1 cm²) and Ag/AgCl (in saturated 3.0 M KCl) served as the counter and reference electrodes, respectively. Catalyst inks of RI-SAC and commercial 20 wt% Pt/C were prepared by mixing 10 mg of each catalyst with 20 µL of DI water, followed by the addition of 5 wt% Nafion ionomer solution and IPA. The mixture was ultrasonicated to achieve a homogeneous dispersion. The working electrode was then prepared by drop-casting 5 µL of the ink onto a glassy carbon disk and drying it under ambient conditions. A diluted Pt/C(1.87) ink with a Pt loading matching that of RI-SAC was prepared by mixing 7 mg of the catalyst with 20 µL of DI water, followed by the addition of 5 wt% Nafion ionomer solution and sufficient IPA to adjust the concentration as necessary. After ultrasonication, 2.23 µL of the ink was drop-cast onto the working electrode and dried in the same manner. The electrochemical measurements were performed in 1.0 M KOH solution at 25°C. The potential of the reference electrode was calibrated against the reversible hydrogen electrode (RHE), and the conversion factor was determined to be in the range of + 1.020 to + 1.025 V in 1.0 M KOH. Accordingly, all potentials in this study were converted to the RHE scale using Eq. (1): $$\:{\text{E}}_{\text{R}\text{H}\text{E}}\:=\:{\text{E}}_{\text{A}\text{g}/\text{A}\text{g}\text{C}\text{l}}\:+\:\left(1.020\:\sim\:1.025\right)\:\text{V}\:\:\:\:\:\:\:\:\:\:\left(1\right)$$ HER measurements The HER measurements were conducted under H 2 -saturated conditions. LSV tests were performed at a scan rate of 5 mV s − 1 and a rotation speed of 1,600 rpm to evaluate the polarization behavior. CP measurements were subsequently carried out under the same gas-saturation and rotation conditions by maintaining a constant current density of 10 mA cm − 2 for 10 h to assess the durability of RI-SAC. Tafel slopes were obtained from the linear region of the η–log( I ) plots derived from the LSV data. As the geometric area was fixed at 0.196 cm 2 , the use of current instead of current density does not influence the calculated slope ( j = I A − 1 ). The TOF was calculated from CO-stripping measurements. After thorough Ar purging, pre-CV scans were performed to clean the catalyst surface, and the potential was held at 0.05 V RHE for 60 s. While maintaining this potential, high-purity CO gas was bubbled through the electrolyte for 15 min to allow surface adsorption, followed by Ar purging to remove the residual CO. The CO oxidation region was identified by comparing the first and subsequent CV cycles. The TOF was determined using Eq. (2): $$\:\text{T}\text{O}\text{F}\:\left({\text{s}}^{-1}\right)\:=\:\frac{I\:\times\:\:FE}{n\:\times\:\:F\:\times\:\:{N}_{\text{a}\text{c}\text{t}\text{i}\text{v}\text{e}}}\:\:\:\:\:\:\:\:\:\:\left(2\right)$$ where I is the current at a given potential ( A ), FE is assumed to be 1, n is the electron transfer number (2 for HER), and F is the Faraday constant (96,485 C mol − 1 ). The number of active sites ( N active ) was obtained using Eq. (3): $$\:{N}_{\text{a}\text{c}\text{t}\text{i}\text{v}\text{e}}\:=\:\frac{\text{E}\text{C}\text{S}\text{A}\:\times\:\:\text{P}\text{t}\left(111\right)\:\text{a}\text{t}\text{o}\text{m}\text{i}\text{c}\:\text{d}\text{e}\text{n}\text{s}\text{i}\text{t}\text{y}}{{N}_{\text{A}\text{v}\text{o}\text{g}\text{a}\text{d}\text{r}\text{o}}}\:\:\:\:\:\:\:\:\:\:\left(3\right)$$ ECSA (m 2 ) was determined from the integrated charge of the CO-stripping region. The atomic density of Pt(111) is reported as 1.25 × 10 19 atoms m − 2 in the literature, and N Avogadro represents the Avogadro number (6.022 × 10 23 atoms mol − 1 ). ORR measurements The ORR measurements were conducted under O 2 -saturated conditions. LSV tests were performed at a scan rate of 5 mV s − 1 and rotation speed of 1,600 rpm to evaluate the polarization behavior. The electron transfer number ( n ) was calculated using the K–L Eq. (4): $$\:\frac{1}{j}\:=\:\frac{1}{{j}_{\text{k}}}\:+\:\frac{1}{B\:\times\:\:{\omega\:}^{\frac{1}{2}}}\:\:\:\:\:\:\:\:\:\:\left(4\right)$$ $$\:B=0.62\:\times\:\:n\:\times\:\:F\:\times\:\:{D}_{0}^{\frac{2}{3}}\:\times\:\:{\nu\:}^{-\frac{1}{6}}\:\times\:{C}_{0}\:\:\:\:\:\:\:\:\:\left(5\right)$$ where j is the measured current density (A cm − 2 ), j k is the kinetic current density, ω is the electrode rotation rate (rad s − 1 ), F is the Faraday constant (96,485 C mol − 1 ), D 0 is the diffusion coefficient of O 2 , ν is the kinematic viscosity of the electrolyte, and C 0 is the bulk concentration of O 2 , and n was determined from the slope of the K–L plots ( j − 1 vs. ω −1/2 ) at different potentials. Declarations Data availability statement The datasets used and/ or analyzed during the current study available from the corresponding author on reasonable request. Acknowledgement This work was supported by the Korea Atomic Energy Research Institute (KAERI) Institutional Program (NTIS No. 2710087432). And this work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2023–00244981). This work was also supported by project for Collabo R&D between Industry, University, and Research Institute funded by Korea Ministry of SMEs and Startups in 2025 (RS-2025-02306589). Author information These authors contributed equally: Soyeon Si, Dami Yun. Author contributions S.L. and J.-M.Y. supervised the project. D.Y. performed the synthesis. S.S. and D.Y. performed the characterizations. S.S. performed electrochemical tests. Y.-M.L., H.B.K., S.-H.O., B.K., H.K., J.H.P. and I.K. performed data analyses. S.S. and D.Y. co-wrote the paper. All authors discussed the results and commented on the manuscript. 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07:29:05","extension":"png","order_by":13,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":74850,"visible":true,"origin":"","legend":"","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/1f69b6fcc2b05054898cacdb.png"},{"id":97768307,"identity":"e4f83d7b-81b9-4f12-828e-2b719c1822e1","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"xml","order_by":14,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":132637,"visible":true,"origin":"","legend":"","description":"","filename":"NCOMMS25981830structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/1e2b772717648f5fa3d30f05.xml"},{"id":97768308,"identity":"aad9258f-61ad-4dff-bd71-f619d8a4a566","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"html","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":141172,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/c6936c296c60bf9846104ab9.html"},{"id":97768289,"identity":"f8e0241c-202b-4c3b-b000-e49628782599","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":451851,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematics of the e-beam-induced formation of Pt\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e in a frozen hybrid matrix. \u003c/strong\u003e(a) Macroscopic illustration of Pt precursor reduction under e-beam irradiation in a frozen hybrid matrix. (b) Microscopic schematic illustrating the frozen hybrid matrix configuration and (c) radiolytic reduction process.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/cee4f2fba903c8038528e587.png"},{"id":97768294,"identity":"be788396-3cf5-4af4-b8fe-3feb19ee7edc","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":447805,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStructural and chemical characteristics of RI-SAC.\u003c/strong\u003e (a) XRD pattern confirming the single-atom dispersion of Pt in RI-SAC. (b) TEM images (left and right scale bars = 10 and 5 nm, respectively) and (c) EDS elemental mappings of RI-SAC (scale bars = 20 nm). (d) Pt 4f XPS spectra of RI-SAC and Pt/C. (e) XANES and (f) EXAFS spectra of Pt foil, RI-SAC, and PtO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/55ddaef8b43b1972480980ed.png"},{"id":97768292,"identity":"2cf79bc3-06bf-4cc4-a9df-69047de69e78","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":300584,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectrocatalytic performance toward the HER. \u003c/strong\u003e(a) LSV curves in H\u003csub\u003e2\u003c/sub\u003e-saturated 1.0 M KOH solution. (b) Corresponding Tafel plots. (c) TOF values calculated in the overpotential range of 50–300 mV\u003csub\u003eRHE\u003c/sub\u003e. (d) CP measurements over 10 h at 10 mA cm\u003csup\u003e−2\u003c/sup\u003e. (e) Performance retention after CP. (f) LSV curves recorded after CP. (g) Comparison of TOFs between RI-SAC and previously reported catalysts. Data points labeled “Refs. S1–S9” correspond to values taken from Supplementary References 1–9.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/419f2e5b5fbeb5b846189761.png"},{"id":97896668,"identity":"6c0a6a42-f4d1-429a-b655-79955222ce2a","added_by":"auto","created_at":"2025-12-10 15:36:52","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":135409,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eElectrocatalytic performance toward the ORR. \u003c/strong\u003e(a) LSV curves in O\u003csub\u003e2\u003c/sub\u003e-saturated 1.0 M KOH solution. (b) Comparison of mass activity between RI-SAC and Pt/C at 0.85 V\u003csub\u003eRHE\u003c/sub\u003e. (c) Comparison of mass activity between RI-SAC and reported Pt-based catalysts. Data points labeled “Refs. S10–S24” correspond to values taken from Supplementary References 10–24. (d) K–L plots recorded at 0.6–0.8 V\u003csub\u003eRHE\u003c/sub\u003e at rotation rates of 400–2,000 rpm. (e) Electron transfer number calculated from the K–L plots derived at rotation rates of 400–2,000 rpm.\u0026nbsp;\u003c/p\u003e","description":"","filename":"floatimage41.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/7edf26dbe0184bec2b3ad8ba.png"},{"id":97768300,"identity":"4b6231ed-a736-4d51-a83a-4ed377176216","added_by":"auto","created_at":"2025-12-09 07:28:59","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":442975,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eLarge-scale synthesis of Pt SACs under continuous e-beam irradiation. \u003c/strong\u003e(a) 3D dose-mapping schematic of a single tray. (b) Lateral and traveling dose uniformity. (c) Spatial dose distribution measured using a B3000 film array. (d) Photograph of Pt SACs obtained from large-scale synthesis. (e) Estimated production capacity based on the optimized e-beam process.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/93048baf4642f0fa8ed7811c.png"},{"id":99795707,"identity":"5aefbe03-e633-45cd-ba75-138b975e81ad","added_by":"auto","created_at":"2026-01-08 13:39:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2474974,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/e2dc8003-ff1e-4db1-9f60-88586433d6ee.pdf"},{"id":97897424,"identity":"0010ad00-35a4-4c78-aeb4-8b681b1ed713","added_by":"auto","created_at":"2025-12-10 15:37:49","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1742652,"visible":true,"origin":"","legend":"Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices","description":"","filename":"SupplymentaryInformationPilotScaleContinuousSynthesisofPtSingleAtomCatalystsviaElectronBeamProcessinginIceMatrices.docx","url":"https://assets-eu.researchsquare.com/files/rs-8276245/v1/db062beca3dcd783f563fc01.docx"}],"financialInterests":"\u003cb\u003eYes\u003c/b\u003e there is potential Competing Interest.\nThe authors declare the following competing interests: D.Y., Y.-M.L., H.B.K., B.K., H.K., S.L., and J.-M.Y. are inventors on a patent application related to this work that has been filed by the Korea Atomic Energy Research Institute (KAERI) in Korea (Application No. 10-2025-0065141). The authors that are not named in the patent declare no other competing interests.","formattedTitle":"Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSingle-atom catalysts (SACs) have emerged as an effective strategy to maximize the utilization of precious metals in catalytic reactions. Catalytic reactions generally occur on the catalyst surface, thereby leaving bulk-embedded atoms largely inaccessible\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Consequently, achieving nearly 100% dispersion on the surface of SACs is crucial for enhancing catalytic activity. SACs contain isolated metal atoms that behave as individual active sites during electrochemical catalysis. This atomic configuration restricts the adsorption modes of reactants, thereby improving reaction selectivity\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. A representative example of such enhanced selectivity is the two-electron oxygen reduction reaction (2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR) that produces H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e5, 6\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eHowever, the isolated metal atoms in SACs are thermodynamically unstable and tend to aggregate during synthesis or under reaction conditions to reduce the total free energy. Individual atoms may also detach from the support under reaction conditions\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. The effective utilization of single atoms as active sites may be achieved by (1) ensuring the uniform dispersion of single atoms and (2) firmly anchoring them onto the support, both of which are key to the synthesis and practical application of SACs. In particular, uniform dispersion and strong metal\u0026ndash;support anchoring are essential to suppress atomic migration and nanoparticle formation during precursor reduction. At present, the scalable synthesis of catalysts that meet these conditions remains a considerable challenge.\u003c/p\u003e\u003cp\u003eSynthesis strategies for SACs incorporating the key factors mentioned above have been extensively developed in recent years. For instance, atomic layer deposition exploits self-limiting surface reactions to enable atomic-scale growth with submonolayer precision\u003csup\u003e\u003cspan additionalcitationids=\"CR10 CR11 CR12 CR13\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Wet impregnation, followed by drying and thermal activation, can anchor isolated metal atoms through precursor\u0026ndash;support interactions\u003csup\u003e\u003cspan additionalcitationids=\"CR16 CR17 CR18 CR19 CR20 CR21\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Sputtering-based physical vapor deposition, a top-down synthesis strategy, provides a feasible route to produce SACs, as the plasma intensity applied to the target metal can be finely tuned to eject single atoms and deposit them at the atomic scale onto a support\u003csup\u003e\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eIntegrated strategies have also been devised to enable both the high dispersion and strong anchoring of single atoms. In such strategies, metal ions are uniformly embedded within precursors such as polymers, small molecules, metal\u0026ndash;organic frameworks, or organometallic complexes, and subsequent pyrolysis under controlled atmospheres yields atomically dispersed catalysts\u003csup\u003e\u003cspan additionalcitationids=\"CR27 CR28 CR29\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Recent reports have demonstrated the feasibility of the kilogram-scale production of SACs through mechanochemical approaches. For instance, ball milling, a typical mechanochemical method, employs impact and shear forces generated between colliding particles to drive solid-state reactions\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan additionalcitationids=\"CR32 CR33\" citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eSuch methods typically rely on batch-to-batch systems, thereby posing challenges to continuous synthesis and reducing process efficiency. Production capacity is also restricted by the reactor size and throughput, as scaling up requires multiple units, creating spatial and economic limitations. Scale-up also introduces additional challenges such as high-temperature operation, complex post-treatment, particle aggregation, poor uniformity control, and metal contamination. Therefore, alternative and more practical approaches should be developed to enable the scalable production of SACs without compromising their atomic dispersion.\u003c/p\u003e\u003cp\u003eTo bridge this gap in the literature and address the limitations of current techniques, we propose a new approach that employs the radiolytic reduction of metal ions to synthesize SACs. Upon irradiation, water is radiolyzed, generating hydrated electrons (e\u003csub\u003eaq\u003c/sub\u003e⁻) and hydrogen radicals (H\u0026middot;), which act as strong reducing species that convert metal precursors into their metallic state.\u003c/p\u003e\u003cp\u003eThis process does not require chemical reductants or stabilizers, enabling high-purity catalyst synthesis. It also offers straightforward process control that is well suited for mass production when integrated with a continuous electron-accelerator conveyor system. It can also induce uniform and rapid reduction reactions throughout the entire reaction volume. Leveraging these advantages, irradiation with electron beams (e-beams) or gamma rays has been widely explored for Pt nanoparticle synthesis; however, the reduced Pt atoms readily migrate and aggregate into nanoparticles, demonstrating limited control at the single-atom level.\u003c/p\u003e\u003cp\u003eTo overcome this issue, we irradiated a frozen Pt precursor solution with e-beams, effectively suppressing atomic diffusion while maintaining the reduction reaction environment. In other words, preventing reduced Pt atoms from aggregating or growing into Pt\u003csub\u003ex\u003c/sub\u003e (x\u0026thinsp;\u0026ge;\u0026thinsp;2) clusters serves as the core strategy of our e-beam-based SAC synthesis. We confirmed that Pt atoms were stabilized in the single-atom form without growing into nanoparticles, and demonstrated that the mass production of Pt single atoms (Pt\u003csub\u003e1\u003c/sub\u003e) is possible using an electron-accelerator conveyor system. Furthermore, the e-beam-reduction mechanism can also be applied to various metal precursors such as Pd and Ir, demonstrating that this approach can be extended to a universal SAC synthesis platform.\u003c/p\u003e\u003cp\u003eUsing this system, we successfully developed a radiation-induced SAC (RI-SAC). RI-SAC exhibited enhanced catalytic performance compared with commercial Pt/C in both the hydrogen evolution reaction (HER) and the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR, which are the key processes in water electrolysis and H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production, respectively. Notably, RI-SAC demonstrated remarkable scalability for mass production. The e-beam conveyor system enabled the continuous fabrication of approximately 446 kg of catalyst per day. This work is the first to report a significant advance in SAC synthesis and to demonstrate a production capacity suitable for industrial-scale demand. By satisfying the key requirements of SACs, including high atomic dispersion, strong metal\u0026ndash;support interactions, and large-scale producibility, RI-SAC provides a robust and scalable platform for the advancement of the catalyst industry.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents a stepwise overview of how Pt₁ can be generated within a Pt-precursor/carbon/water mixture frozen at \u0026minus;\u0026thinsp;30\u0026deg;C (hereafter referred to as the frozen hybrid matrix) under e-beam irradiation, integrating both macroscopic and microscopic perspectives. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea illustrates the macroscopic sequence in which radiolytically generated reducing species (e\u003csub\u003eaq\u003c/sub\u003e⁻ and H\u0026middot;) locally reduce Pt precursors within the immobilized frozen hybrid matrix\u003csup\u003e\u003cspan additionalcitationids=\"CR36 CR37\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e, followed by anchoring of the resulting Pt₁ species onto carbon or nitrogen-doped sites during thawing. The frozen hybrid matrix effectively restricts long-range molecular mobility of Pt atoms and Pt precursors, thereby suppressing aggregation pathways that require translational accessibility\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb expands this structural concept to the microscopic scale. During ice-crystal growth, micro-brine pockets form as solutes are excluded from advancing ice fronts\u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. and carbon particles are displaced toward these solute-rich liquid domains where they may reside at or within the brine-pocket regions\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. Consequently, the Pt precursor becomes relatively enriched within the micro-brine pockets\u0026mdash;and in the ultrathin interfacial water layers surrounding carbon surfaces\u0026mdash;while its concentration within the pure-ice lattice remains minimal due to the strong exclusion of ionic species\u003csup\u003e\u003cspan additionalcitationids=\"CR45 CR46 CR47 CR48 CR49\" citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. This spatial segregation, together with the markedly reduced long-range mobility of Pt-containing species imposed by the frozen matrix, creates conditions in which reduced Pt atoms rarely encounter one another, thereby lowering the likelihood of cluster formation.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec illustrates the reduction pathways within the frozen hybrid matrix across three micro-domains\u0026mdash;pure ice, micro-brine pockets, and carbon-adjacent regions. E-beam irradiation generates track structures composed of spurs that produce radiolytic reducing species such as e\u003csub\u003eaq\u003c/sub\u003e⁻ and H\u0026middot;\u003csup\u003e51\u003c/sup\u003e. Carbon particles additionally emit low-energy secondary electrons or backscattered electrons (emitted electrons)\u003csup\u003e\u003cspan additionalcitationids=\"CR53 CR54\" citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. These electrons directly reduce Pt precursors that accumulate at the carbon\u0026ndash;ice interface because of their close proximity to the emitting surfaces. In contrast, radiolytic species, although exhibiting limited mobility at cryogenic temperatures, can still diffuse over several nanometers within spur regions or interfacial quasi-liquid layers (QLLs)\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e, \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e, enabling reduction of Pt precursors located in micro-brine pockets as well as in carbon-adjacent regions, where precursor concentrations are comparatively higher.\u003c/p\u003e\u003cp\u003eTaken together, the distribution of precursors within micro-brine pockets, the spatially confined production and short-range transport of reducing species originating from spurs and tracks, the supplementary contribution of emitted electrons near carbon surfaces, and the overall suppression of mobility under frozen conditions collectively act to reduce the likelihood of aggregation of reduced Pt species. These combined factors suggest that e-beam irradiation under frozen-state conditions can provide a physicochemically favorable environment for the formation and stabilization of Pt single atoms. Building on this mechanistic basis, we applied frozen-state e-beam irradiation to the frozen hybrid matrix to synthesize isolated Pt species on the N-doped carbon support, the detailed analysis of which is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo elucidate the structural and chemical characteristics of the synthesized catalyst, we conducted conventional physicochemical characterizations. Quantitative analysis by inductively coupled plasma optical emission spectrometry (ICP-OES) revealed that RI-SAC contains approximately 1.87 wt% Pt, further confirming the successful incorporation of atomically dispersed Pt species.\u003c/p\u003e\u003cp\u003eThe atomic dispersion of Pt in RI-SAC was verified by X-ray diffraction (XRD) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The two broad peaks at approximately 25\u0026deg; and 43\u0026deg; (2θ) correspond to the (002) and combined (100)/(101) planes of graphitic carbon, respectively\u003csup\u003e\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e. Although the sharp metallic Pt peaks of commercial Pt/C were detected, RI-SAC showed no distinct Pt reflections, indicating the presence of atomically dispersed Pt rather than clustered or particulate forms.\u003c/p\u003e\u003cp\u003eHigh-angle annular dark-field scanning transmission electron microscopy (HAADF\u0026ndash;STEM) provided direct visual evidence of the single-atom dispersion of Pt (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Bright atomic-scale spots were homogeneously distributed over the carbon region, consistent with the presence of isolated Pt atoms. Elemental mapping by energy-dispersive X-ray spectroscopy (EDS) confirmed that these bright features correspond to Pt single atoms (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec), while the presence of nitrogen signals indicated successful N-doping of the carbon framework.\u003c/p\u003e\u003cp\u003eThe chemical state of Pt was then examined by X-ray photoelectron spectroscopy (XPS) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed). Pt/C exhibited a prominent metallic Pt\u003csup\u003e0\u003c/sup\u003e signal in the Pt 4f region, whereas RI-SAC showed no detectable Pt\u003csup\u003e0\u003c/sup\u003e component, suggesting that Pt exists predominantly in an oxidized form. To obtain an in-depth understanding of the interfacial interaction between atomically dispersed Pt sites and nitrogen functionalities within the carbon support, we compared the N 1s XPS profiles of RI-SAC and N-doped carbon (Supplementary Fig.\u0026nbsp;1). The exclusive appearance of a new peak at ~\u0026thinsp;400.1 eV in the N 1s XPS profile of RI-SAC indicates nitrogen incorporation and the formation of N\u003csub\u003ex\u003c/sub\u003e\u0026ndash;Pt coordination bonds, reflecting strong Pt\u0026ndash;N interactions.\u003c/p\u003e\u003cp\u003eTo investigate the electronic structure and coordination state of Pt, we performed Pt L\u003csub\u003e3\u003c/sub\u003e-edge X-ray absorption spectroscopy (XAS). The X-ray absorption near-edge structure (XANES) spectra revealed that the white-line intensity of RI-SAC was located between those of Pt foil and PtO\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee), indicating partially oxidized Pt species with an intermediate valence between 0 and +\u0026thinsp;4. This finding is in excellent agreement with the XPS results. Extended X-ray absorption fine structure (EXAFS) analysis revealed no Pt\u0026ndash;Pt coordination peak typically observed for metallic Pt, confirming the atomically isolated nature of Pt in RI-SAC (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef). These results collectively establish that Pt is atomically anchored on the N-doped carbon support in an oxidized single-atom configuration. The XAS results are consistent with the structural features revealed by XRD and TEM.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eGiven the pivotal role of the HER in water electrolysis, the catalytic performance of RI-SAC was evaluated to assess its intrinsic activity for this reaction. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, RI-SAC exhibited a higher overpotential than commercial Pt/C at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, reflecting its lower HER activity. This result is reasonable because the Pt loading of RI-SAC (\u0026asymp;\u0026thinsp;6.12 \u0026micro;g\u003csub\u003ePt\u003c/sub\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) is approximately 10.7 times lower than that of Pt/C, which contains\u0026thinsp;\u0026asymp;\u0026thinsp;65.4 \u0026micro;g\u003csub\u003ePt\u003c/sub\u003e cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (Supplementary Fig.\u0026nbsp;3).\u003c/p\u003e\u003cp\u003eThe distinct mechanistic nature of single-atom catalysis also accounts for this difference. In nanoparticle catalysts, adjacent active sites allow both Volmer\u0026ndash;Tafel and Volmer\u0026ndash;Heyrovsky pathways, enabling efficient electron transfer and H\u0026ndash;H bond formation. By contrast, SACs possess isolated metal centers that render the Tafel step impossible, predominantly following the Volmer\u0026ndash;Heyrovsky route\u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. Such mechanistic constraints inevitably lead to higher overpotentials and slower hydrogen evolution kinetics. Therefore, a comparative evaluation of SACs and nanoparticle catalysts in terms of Tafel slope and turnover frequency (TOF) is crucial to understand their reaction kinetics and intrinsic site activity. The combined analysis of these parameters provides quantitative insights into the inherent activity and kinetic behavior of each catalyst.\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the two catalysts exhibit nearly identical Tafel slopes, suggesting that charge transfer in RI-SAC occurs efficiently despite its mechanistic constraints. Comparison of the TOFs calculated at six overpotentials (50\u0026ndash;300 mV\u003csub\u003eRHE\u003c/sub\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec) revealed that the TOFs of RI-SAC are 3.15\u0026ndash;3.6 times higher than those of Pt/C (7.63 s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 100 mV\u003csub\u003eRHE\u003c/sub\u003e, 42.0 s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at 300 mV\u003csub\u003eRHE\u003c/sub\u003e). On average, the TOF of RI-SAC is enhanced by approximately 3.3-fold compared with that of Pt/C across the overpotential range investigated.\u003c/p\u003e\u003cp\u003eThe TOF performance of RI-SAC demonstrates that each of its active sites has higher intrinsic reactivity than those of Pt/C, which can be attributed to the superior atom utilization efficiency of its single-atom architecture. These results indicate that the catalyst not only features atomically uniform dispersion but also high activity at individual atomic sites. This enhanced intrinsic activity likely originates from the strong coordination between isolated Pt atoms and the N-doped carbon support, forming stable M\u0026ndash;N\u003csub\u003ex\u003c/sub\u003e moieties that optimize the electronic structure for the alkaline HER.\u003c/p\u003e\u003cp\u003eTo evaluate the durability of RI-SAC, we conducted chronopotentiometry (CP) measurements for 10 h. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed, RI-SAC maintains a stable current response throughout its long-term operation. According to the CP results, the performance retention of RI-SAC (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee), at 73.3%, is higher than that of Pt/C (60.9%), indicating a smaller increase in overpotential during long-term electrolysis.\u003c/p\u003e\u003cp\u003eAfter the CP test, the HER polarization linear sweep voltammetry (LSV) curve (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef) was re-evaluated. Pt/C exhibited noticeable performance degradation, whereas RI-SAC maintained and even showed a slight improvement in its HER activity. This enhancement is attributed to the partial aggregation of isolated Pt atoms into small clusters during operation, which transiently activates both the Volmer\u0026ndash;Tafel and Volmer\u0026ndash;Heyrovsky pathways, thereby improving the overall reaction efficiency.\u003c/p\u003e\u003cp\u003eTo investigate the effect of Pt loading amount on the catalytic performance, we conducted additional electrochemical measurements under the same Pt loading conditions (Supplementary Figs.\u0026nbsp;4\u0026ndash;6), considering the substantial difference in Pt content between RI-SAC and Pt/C. Under these normalized conditions, RI-SAC consistently exhibited superior HER performance across all metrics examined. Notably, commercial Pt/C with a reduced Pt loading (1.87 wt% Pt, hereafter denoted as Pt/C(1.87)) demonstrated pronounced performance decay, retaining only 50.4% of its initial activity after 10 h of CP. By contrast, RI-SAC exhibited remarkable stability and sustained catalytic efficiency, unambiguously demonstrating its intrinsic durability advantage over conventional Pt catalysts at comparable metal loadings. To further highlight the outstanding catalytic attributes of RI-SAC, we benchmarked its TOF against those of recently reported HER catalysts. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg, compared with other catalysts, RI-SAC delivers a substantially higher TOF value at an overpotential of 100 mV\u003csub\u003eRHE\u003c/sub\u003e, underscoring its exceptional intrinsic reactivity and efficient atomic utilization.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eOwing to the geometric configuration of the single-atom Pt sites, molecular O\u003csub\u003e2\u003c/sub\u003e can only adsorb onto the catalyst on an end-on (Pauling) fashion, which favors the associative pathway for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. To investigate how RI-SAC leverages this geometric feature to selectively drive the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR, we conducted comprehensive electrochemical measurements.\u003c/p\u003e\u003cp\u003eRI-SAC exhibited a half-wave potential of 0.90 V\u003csub\u003eRHE\u003c/sub\u003e, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, which is slightly lower than that of commercial Pt/C (0.95 V\u003csub\u003eRHE\u003c/sub\u003e), indicating its lower ORR activity. Such a result is reasonable and can be attributed to the absolute difference in Pt loading, as mentioned earlier. To compensate for differences in loading amount, we normalized the catalytic performance of the catalysts to their Pt loading, and consequently mass activity was used as a reliable metric to evaluate the intrinsic catalytic performance of both materials (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). At 0.85 V\u003csub\u003eRHE\u003c/sub\u003e, RI-SAC achieved a mass activity of approximately 7.0 A mg\u003csub\u003ePt\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e, whereas Pt/C delivered a mass activity of approximately 0.8 A mg\u003csub\u003ePt\u003c/sub\u003e\u003csup\u003e\u0026minus;1\u003c/sup\u003e, indicating that RI-SAC is about 8 times more active than Pt/C on a mass basis. To validate its electrochemical superiority, we benchmarked the mass activity of RI-SAC against those of recently reported catalysts. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec shows that RI-SAC delivers the highest mass activity among recently reported ORR catalysts.\u003c/p\u003e\u003cp\u003eThe selectivity of RI-SAC toward the 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e ORR was investigated by measuring its limiting current density at five rotation speeds ranging from 400 to 2,000 rpm (Supplementary Fig.\u0026nbsp;7). The resulting Kouteck\u0026yacute;\u0026ndash;Levich (K\u0026ndash;L) plots are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed. From the K\u0026ndash;L analysis, the electron transfer number (n) was determined to be approximately 2.3 within the potential range of 0.6\u0026ndash;0.8 V\u003csub\u003eRHE\u003c/sub\u003e, where the ORR predominantly occurs (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). This finding confirms that RI-SAC primarily follows a 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e pathway, enabling highly selective H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e formation. Overall, RI-SAC displays well-balanced performance across both activity and selectivity, rendering it a promising catalyst for cost-effective and high-purity H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production with applicability to semiconductor, environmental, and energy-conversion technologies.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo assess the feasibility of the large-scale synthesis of Pt SACs using a 10 MeV electron accelerator, we systematically investigated the dose uniformity of the irradiation process and its applicability to continuous production (Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea\u0026ndash;e). All experiments were conducted at a target dose of 50 kGy, which is identical to the optimized condition used for small-scale Pt SAC synthesis. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea shows the experimental configuration for 3D dose mapping within a single tray (80 \u0026times; 60 \u0026times; 10 cm\u003csup\u003e3\u003c/sup\u003e), with B3000 radiochromic dosimetry films placed at 27 positions in a 3 \u0026times; 3 \u0026times; 3 grid along the x-, y-, and z-axes. This configuration enabled the quantitative assessment of the absorbed dose distribution and analysis of electron penetration and attenuation behavior during irradiation.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb presents the results of the lateral and traveling dose uniformity measurements. Lateral dose uniformity, which indicates dose flatness across the beam extraction width, exhibited a mean absorbed dose of 49.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.47 kGy (\u0026asymp;\u0026thinsp;0.94%), with a\u0026thinsp;~\u0026thinsp;1.5 m flat-top region fully encompassing the tray width, confirming highly uniform surface irradiation. Traveling dose uniformity, which was evaluated along the conveyor direction to determine inter-tray consistency, showed a mean of 100.22%, standard deviation of 1.04%, and range of 98.4\u0026ndash;102.6% (within \u0026plusmn;\u0026thinsp;2%). These results demonstrate that uniform irradiation is maintained even under continuous multi-tray operation. Overall, the excellent agreement between the beam scanning frequency and conveyor speed ensured highly stable and reproducible irradiation conditions suitable for industrial-scale processing\u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec presents the 3D dose distribution obtained from the grid defined in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea. The mean absorbed dose was 47.60\u0026thinsp;\u0026plusmn;\u0026thinsp;1.66 kGy, with a maximum dose of 51.1 kGy (middle-layer center) and a minimum dose of 45.1 kGy (bottom-layer right corner). The dose uniformity ratio (DUR) was 1.133, with a coefficient of variation of 3.5% and standard deviation of 1.66 kGy. These values are below the recommended limit of 1.30 for radiation processing and exceed the ISO 11137-1:2025 criterion (1.25)\u003csup\u003e\u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u003c/sup\u003e, indicating superior dose homogeneity throughout the irradiated volume.\u003c/p\u003e\u003cp\u003eThe spatial dose variations in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec are consistent with the characteristic percentage depth dose profile of a 10 MeV e-beam. Reductions in surface dose arise from a build-up deficiency before the maximum dose depth (d\u003csub\u003emax\u003c/sub\u003e), where electronic equilibrium is achieved by forward-scattered electrons, is reached. Beyond d\u003csub\u003emax\u003c/sub\u003e (~\u0026thinsp;2 cm), dose attenuation occurs\u003csup\u003e\u003cspan citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u003c/sup\u003e. In the bottom layer, central dose enhancement is attributed to backscattered electrons from the Al tray, whereas dose reduction at the edges is caused by lateral electron loss and roll-off effects. The central region exhibits a relatively higher absorbed dose owing to forward electron scattering and energy deposition concentration\u003csup\u003e\u003cspan additionalcitationids=\"CR64\" citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e. These distributions are governed by the electron incidence angle, tray material, and scattering dynamics, demonstrating both the physical consistency and precise dose control of the process.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed summarizes the results of a scaled-down, multitray validation experiment performed under full-scale conditions (50 kGy, 1 min intertray interval). Four trays produced a total of 1,253 g of Pt SACs (~\u0026thinsp;313 g per tray), confirming uniform synthesis efficiency across trays. The first tray required 16 min from entry to exit (including irradiation and transit), after which one tray containing\u0026thinsp;~\u0026thinsp;313 g of catalyst was continuously delivered every minute. These findings verify the feasibility of high-throughput, continuous operation under stable irradiation parameters.\u003c/p\u003e\u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee presents the estimated production capacity of the proposed system under the validated operational conditions. Application of the same process parameters yielded predicted production rates of ~\u0026thinsp;14.1 kg h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, ~\u0026thinsp;446.38 kg day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, ~\u0026thinsp;13.53 ton month\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and ~\u0026thinsp;164.6 ton year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to an over-400-fold increase compared with previously reported large-scale SAC synthesis methods, which achieve production capacities in the order of 1 kg day\u003csup\u003e\u0026minus;\u0026thinsp;1 27, \u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e. These results confirm that the e-beam-driven synthesis approach developed in this work provides a highly efficient and scalable platform for the industrial-scale production of Pt SACs.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this work, we successfully synthesized a Pt SAC (RI-SAC) through a radiation-induced strategy conducted in a frozen-state environment. During e-beam irradiation, the generated e\u003csub\u003eaq\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and H\u0026middot; reduced the PtCl\u003csub\u003e6\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e precursor to metallic Pt\u003csup\u003e0\u003c/sup\u003e, thereby achieving the atomic-level dispersion of Pt atoms. In addition, local aggregation that could occur during irradiation was effectively suppressed by the frozen environment and the anchoring effect of nitrogen dopants.\u003c/p\u003e\u003cp\u003eThe synthesized RI-SAC exhibited outstanding catalytic activity toward both the HER and ORR in an alkaline electrolyte. For the HER, the TOF of RI-SAC was up to 3.6 times higher than that of commercial Pt/C, and the catalyst demonstrated 73.3% performance retention after a 10 h CP test at 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e. For the ORR, the mass activity of RI-SAC was approximately 8 times greater than that of Pt/C, and the catalyst followed a distinct 2e\u003csup\u003e\u0026minus;\u003c/sup\u003e reaction pathway, confirming that the intrinsic single-atom reaction mechanism was preserved.\u003c/p\u003e\u003cp\u003eIn terms of scalability, the proposed conveyor-based synthesis process can continuously produce approximately 446.38 kg day\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (equivalent to ~\u0026thinsp;164.6 ton year\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) of catalyst, corresponding to an over-400-fold increase in production efficiency compared with previously reported large-scale SAC synthesis methods, which typically produce the desired materials in the order of 1 kg day\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e. Therefore, the synthesis method presented in this work offers a highly scalable next-generation platform that is applicable to various SACs, including Pd and Ir, and is expected to contribute broadly to the industrial-scale implementation and development of high-efficiency electrocatalysts (Supplementary Fig.\u0026nbsp;9).\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003eMaterials\u003c/h2\u003e\u003cp\u003eAll reagents were used without separate purification. Chloroplatinic acid hexahydrate (H\u003csub\u003e2\u003c/sub\u003ePtCl\u003csub\u003e6\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, 8 wt% in water) and potassium hydroxide (KOH, 90%) were purchased from Sigma-Aldrich. Vulcan XC-72 carbon was purchased from Cabot Corporation. Potassium chloride (KCl, EP, 99.9%), ethyl alcohol (anhydrous, GR, 99.9%) and isopropyl alcohol (IPA, EP, 99.5%) were purchased from DAEJUNG Chemicals\u0026amp;Metals Co., Ltd. 5% Nafion\u0026trade; Dispersion Solution (DE520 CS type) was purchased from FUJIFILM Wako Pure Chemical Corporation. Deionized (DI) water with a resistivity of 18.2 MΩ cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was produced using the Millipore Direct-Q 3 system.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eCatalyst synthesis\u003c/h3\u003e\n\u003cp\u003eN-doped carbon (N-doped Vulcan XC-72) was first prepared by heat-treating Vulcan XC-72 under a 99.9999% NH₃ atmosphere. For the small-scale synthesis of Pt SACs supported on N-doped carbon (RI-SAC), 0.6 g of the N-doped Vulcan XC-72 was dispersed in DI water, and an aqueous H₂PtCl₆\u0026middot;6H₂O precursor solution was added to give a total volume of 30 mL and a Pt precursor concentration of 5.4 mM. The suspension was purged with N\u003csub\u003e2\u003c/sub\u003e for 15 min to remove any dissolved oxygen and subsequently ultrasonicated for 15 min to ensure the homogeneous dispersion of the carbon support. The resulting dispersion was frozen using a laboratory freezer set to \u0026minus;\u0026thinsp;30\u0026deg;C. The frozen sample was then loaded onto an Al tray (dimensions: 60 \u0026times; 80 \u0026times; 8 cm\u003csup\u003e3\u003c/sup\u003e) and irradiated using a 10 MeV electron accelerator (MB10-30/3000; Mevex Corp., Canada; maximum beam current: 3 mA; maximum power: 30 kW). The total irradiation dose was fixed at 50 kGy, a condition that maintains the frozen state throughout e-beam treatment. After e-beam irradiation, the resulting sample was recovered by centrifugation at 3000 rpm for 5 min. To remove unreacted precursor species, the product was re-dispersed and centrifuged twice with DI water, followed by an additional washing step with IPA. The final RI-SAC was obtained by drying the material overnight at 80\u0026deg;C. For the large-scale production, the total reaction volume was increased to 15.5 L while maintaining the same precursor ratio, irradiation dose, and purification procedures as in the small-scale synthesis to ensure consistent synthesis conditions.\u003c/p\u003e\n\u003ch3\u003eAbsorbed dose measurement\u003c/h3\u003e\n\u003cp\u003eThe dependence of the irradiation dose on the under-beam conveyor (UBC) speed in the 10 MeV electron accelerator was measured using a calorimeter (GeV Corp., South Korea). Specifically, the irradiation dose was measured at various UBC speeds, and the relationship between the reciprocal of the UBC speed and irradiation dose was analyzed through linear regression (Supplementary Fig.\u0026nbsp;10a). According to our facility\u0026rsquo;s calibration standard, the measured data were considered valid when the coefficient of determination (R\u0026sup2;) exceeded 0.9990. The high correlation (R\u0026sup2; = 0.9998) obtained in this study confirmed the reliability of the measurements. Finally, the regression function was used to estimate the irradiation dose as a function of UBC speed (Supplementary Fig.\u0026nbsp;10b). For instance, a UBC speed of 0.251 m min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e corresponded to an irradiation dose of 50 kGy.\u003c/p\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eDose mapping and evaluation\u003c/h2\u003e\u003cp\u003eDose mapping and lateral and traveling dose uniformity evaluation were performed using B3000 and CTA dosimetry films, respectively. The irradiation dose was fixed at 50 kGy, consistent with the optimal condition derived from the simulation. After irradiation, the absorbed dose of the B3000 film was evaluated using a Genesys 20 UV\u0026ndash;Vis spectrophotometer (Thermo Fisher Scientific, USA), while the CTA film was analyzed using a Dos\u0026rsquo;ASAP reader (Freiberg Instruments GmbH, Germany).\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003ePhysical characterization\u003c/h3\u003e\n\u003cp\u003eICP-OES was performed using a Thermo Scientific iCAP 6000 Series instrument operated with Ar plasma in axially viewed mode. XRD patterns were recorded on a Bruker D8 Focus diffractometer over the 2θ range of 10\u0026deg;\u0026ndash;90\u0026deg; with a scan speed of 5\u0026deg; min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. TEM was conducted on an FEI Titan\u0026trade; 80\u0026ndash;300 microscope operated in HAADF mode with EDS. The catalyst powders were dispersed in ethyl alcohol, drop-cast onto a holey carbon film (200-mesh Ni grid), and dried under ambient conditions. XPS measurements were performed using a Thermo Scientific K-Alpha spectrometer equipped with a monochromated Al Kα source (1,486.6 eV). The analysis was carried out under an ultrahigh vacuum below 1 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;8\u003c/sup\u003e mbar with an X-ray spot size of approximately 400 \u0026micro;m. Survey and high-resolution spectra (C 1s, N 1s, and Pt 4f) were recorded, and all binding energies were calibrated with respect to the C 1s peak at 284.8 eV. Data acquisition and peak fitting were performed using the Avantage software package. XAS, including XANES and EXAFS, at the Pt L\u003csub\u003e3\u003c/sub\u003e-edge was conducted at the KIST-PAL beamline 1D (EXAFS) of the Pohang Accelerator Laboratory (PLS-II, Korea) in fluorescence mode, with energy calibration using a Pt foil at the absorption edge inflection point. And acquired data was processed and fitted using the Athena software package.\u003c/p\u003e\n\u003ch3\u003eElectrochemical measurements\u003c/h3\u003e\n\u003cp\u003eElectrochemical measurements were carried out using an Autolab PGSTAT204 potentiostat with a conventional three-electrode configuration. A glassy carbon disk electrode (geometric area: 0.196 cm\u003csup\u003e2\u003c/sup\u003e) mounted on a rotating disk electrode setup was employed as the working electrode. A Pt sheet (1 cm\u0026sup2;) and Ag/AgCl (in saturated 3.0 M KCl) served as the counter and reference electrodes, respectively. Catalyst inks of RI-SAC and commercial 20 wt% Pt/C were prepared by mixing 10 mg of each catalyst with 20 \u0026micro;L of DI water, followed by the addition of 5 wt% Nafion ionomer solution and IPA. The mixture was ultrasonicated to achieve a homogeneous dispersion. The working electrode was then prepared by drop-casting 5 \u0026micro;L of the ink onto a glassy carbon disk and drying it under ambient conditions. A diluted Pt/C(1.87) ink with a Pt loading matching that of RI-SAC was prepared by mixing 7 mg of the catalyst with 20 \u0026micro;L of DI water, followed by the addition of 5 wt% Nafion ionomer solution and sufficient IPA to adjust the concentration as necessary. After ultrasonication, 2.23 \u0026micro;L of the ink was drop-cast onto the working electrode and dried in the same manner. The electrochemical measurements were performed in 1.0 M KOH solution at 25\u0026deg;C. The potential of the reference electrode was calibrated against the reversible hydrogen electrode (RHE), and the conversion factor was determined to be in the range of +\u0026thinsp;1.020 to +\u0026thinsp;1.025 V in 1.0 M KOH. Accordingly, all potentials in this study were converted to the RHE scale using Eq.\u0026nbsp;(1):\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\text{E}}_{\\text{R}\\text{H}\\text{E}}\\:=\\:{\\text{E}}_{\\text{A}\\text{g}/\\text{A}\\text{g}\\text{C}\\text{l}}\\:+\\:\\left(1.020\\:\\sim\\:1.025\\right)\\:\\text{V}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(1\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003eHER measurements\u003c/h2\u003e\u003cp\u003eThe HER measurements were conducted under H\u003csub\u003e2\u003c/sub\u003e-saturated conditions. LSV tests were performed at a scan rate of 5 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a rotation speed of 1,600 rpm to evaluate the polarization behavior. CP measurements were subsequently carried out under the same gas-saturation and rotation conditions by maintaining a constant current density of 10 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e for 10 h to assess the durability of RI-SAC. Tafel slopes were obtained from the linear region of the η\u0026ndash;log(\u003cem\u003eI\u003c/em\u003e) plots derived from the LSV data. As the geometric area was fixed at 0.196 cm\u003csup\u003e2\u003c/sup\u003e, the use of current instead of current density does not influence the calculated slope (\u003cem\u003ej\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eI A\u003c/em\u003e\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The TOF was calculated from CO-stripping measurements. After thorough Ar purging, pre-CV scans were performed to clean the catalyst surface, and the potential was held at 0.05 V\u003csub\u003eRHE\u003c/sub\u003e for 60 s. While maintaining this potential, high-purity CO gas was bubbled through the electrolyte for 15 min to allow surface adsorption, followed by Ar purging to remove the residual CO. The CO oxidation region was identified by comparing the first and subsequent CV cycles. The TOF was determined using Eq.\u0026nbsp;(2):\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\text{T}\\text{O}\\text{F}\\:\\left({\\text{s}}^{-1}\\right)\\:=\\:\\frac{I\\:\\times\\:\\:FE}{n\\:\\times\\:\\:F\\:\\times\\:\\:{N}_{\\text{a}\\text{c}\\text{t}\\text{i}\\text{v}\\text{e}}}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(2\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003eI\u003c/em\u003e is the current at a given potential (\u003cem\u003eA\u003c/em\u003e), \u003cem\u003eFE\u003c/em\u003e is assumed to be 1, \u003cem\u003en\u003c/em\u003e is the electron transfer number (2 for HER), and \u003cem\u003eF\u003c/em\u003e is the Faraday constant (96,485 C mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The number of active sites (\u003cem\u003eN\u003c/em\u003e\u003csub\u003eactive\u003c/sub\u003e) was obtained using Eq.\u0026nbsp;(3):\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:{N}_{\\text{a}\\text{c}\\text{t}\\text{i}\\text{v}\\text{e}}\\:=\\:\\frac{\\text{E}\\text{C}\\text{S}\\text{A}\\:\\times\\:\\:\\text{P}\\text{t}\\left(111\\right)\\:\\text{a}\\text{t}\\text{o}\\text{m}\\text{i}\\text{c}\\:\\text{d}\\text{e}\\text{n}\\text{s}\\text{i}\\text{t}\\text{y}}{{N}_{\\text{A}\\text{v}\\text{o}\\text{g}\\text{a}\\text{d}\\text{r}\\text{o}}}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(3\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eECSA (m\u003csup\u003e2\u003c/sup\u003e) was determined from the integrated charge of the CO-stripping region. The atomic density of Pt(111) is reported as 1.25 \u0026times; 10\u003csup\u003e19\u003c/sup\u003e atoms m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e in the literature, and \u003cem\u003eN\u003c/em\u003e\u003csub\u003eAvogadro\u003c/sub\u003e represents the Avogadro number (6.022 \u0026times; 10\u003csup\u003e23\u003c/sup\u003e atoms mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003eORR measurements\u003c/h2\u003e\u003cp\u003eThe ORR measurements were conducted under O\u003csub\u003e2\u003c/sub\u003e-saturated conditions. LSV tests were performed at a scan rate of 5 mV s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and rotation speed of 1,600 rpm to evaluate the polarization behavior. The electron transfer number (\u003cem\u003en\u003c/em\u003e) was calculated using the K\u0026ndash;L Eq.\u0026nbsp;(4):\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$\\:\\frac{1}{j}\\:=\\:\\frac{1}{{j}_{\\text{k}}}\\:+\\:\\frac{1}{B\\:\\times\\:\\:{\\omega\\:}^{\\frac{1}{2}}}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(4\\right)$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$$\\:B=0.62\\:\\times\\:\\:n\\:\\times\\:\\:F\\:\\times\\:\\:{D}_{0}^{\\frac{2}{3}}\\:\\times\\:\\:{\\nu\\:}^{-\\frac{1}{6}}\\:\\times\\:{C}_{0}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(5\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ewhere \u003cem\u003ej\u003c/em\u003e is the measured current density (A cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), \u003cem\u003ej\u003c/em\u003e\u003csub\u003ek\u003c/sub\u003e is the kinetic current density, \u003cem\u003eω\u003c/em\u003e is the electrode rotation rate (rad s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), \u003cem\u003eF\u003c/em\u003e is the Faraday constant (96,485 C mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), \u003cem\u003eD\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e is the diffusion coefficient of O\u003csub\u003e2\u003c/sub\u003e, \u003cem\u003eν\u003c/em\u003e is the kinematic viscosity of the electrolyte, and \u003cem\u003eC\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e is the bulk concentration of O\u003csub\u003e2\u003c/sub\u003e, and \u003cem\u003en\u003c/em\u003e was determined from the slope of the K\u0026ndash;L plots (\u003cem\u003ej\u003c/em\u003e\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e vs. \u003cem\u003eω\u003c/em\u003e\u003csup\u003e\u0026minus;1/2\u003c/sup\u003e) at different potentials.\u003c/p\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets used and/ or analyzed during the current study available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the Korea Atomic Energy Research Institute (KAERI) Institutional Program (NTIS No. 2710087432). And this work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (RS-2023\u0026ndash;00244981). This work was also supported by project for Collabo R\u0026amp;D between Industry, University, and Research Institute funded by Korea Ministry of SMEs and Startups in 2025 (RS-2025-02306589).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThese authors contributed equally: Soyeon Si, Dami Yun.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eS.L. and J.-M.Y. supervised the project. D.Y. performed the synthesis. S.S. and D.Y. performed the characterizations. S.S. performed electrochemical tests. Y.-M.L., H.B.K., S.-H.O., B.K., H.K., J.H.P. and I.K. performed data analyses. S.S. and D.Y. co-wrote the paper. All authors discussed the results and commented on the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare the following competing interests: D.Y., Y.-M.L., H.B.K., B.K., H.K., S.L., and J.-M.Y. are inventors on a patent application related to this work that has been filed by the Korea Atomic Energy Research Institute (KAERI) in Korea (Application No. 10-2025-0065141). The authors that are not named in the patent declare no other competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLiang S, Hao C, Shi Y (2015) The power of single-atom catalysis. 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Nat Commun 13:5721\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-8276245/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8276245/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRadiation-induced reduction is used to synthesize nanoparticles owing to its strong reducing power. However, reduced metal atoms readily aggregate because of their enhanced mobility, localized heating, and precursor migration during synthesis. Consequently, achieving single-atom dispersion remains challenging, highlighting the need for a reaction environment that suppresses diffusion and heat-induced aggregation during irradiation. Here, we present a new radiation-induced synthesis strategy that effectively controls precursor migration and aggregation by employing a frozen-state environment. This approach enables the formation of a radiation-induced single-atom catalyst (RI-SAC) in which Pt precursors are atomically dispersed on the support surface. The resulting RI-SAC exhibits excellent activity toward both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), with a turnover frequency (TOF) and mass activity of up to 3.6 and approximately 8 times higher than those of commercial Pt/C, respectively. Moreover, the process is scalable, continuous, and capable of producing approximately 313 g of catalyst per tray at 1 min intervals, corresponding to a daily yield of nearly 446 kg. Therefore, this synthesis approach provides a versatile and industrially viable platform for the large-scale production of single-atom catalysts (SACs) based on various metals, such as Pd and Ir.\u003c/p\u003e","manuscriptTitle":"Pilot-Scale Continuous Synthesis of Pt Single-Atom Catalysts via Electron-Beam Processing in Ice Matrices","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-09 07:28:54","doi":"10.21203/rs.3.rs-8276245/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3c7d07e6-8b2a-4143-a5ae-7da8a819dc8b","owner":[],"postedDate":"December 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":59294558,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Electrocatalysis"},{"id":59294559,"name":"Physical sciences/Chemistry/Catalysis/Catalyst synthesis"}],"tags":[],"updatedAt":"2026-01-07T06:26:14+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-09 07:28:54","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8276245","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8276245","identity":"rs-8276245","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}