Electrochemical engineering for phase-controlled exfoliation of transition metal dichalcogenides

Electrochemical engineering for phase-controlled exfoliation of transition metal dichalcogenides | 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 Physical Sciences - Article Electrochemical engineering for phase-controlled exfoliation of transition metal dichalcogenides Zhiyuan Zeng, Ju Li, Kian Ping Loh, Bin Liu, Bilu Liu, Xiao Zhang, and 14 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6516593/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 Crystallographic phase engineering is crucial for the precise manipulation of the physical and electronic properties of materials. However, exfoliation of high-phase-purity atomic-layer transition-metal dichalcogenide (TMD) nanosheets remains a challenge. Conventional methods based on alkali metal-ion intercalation (Li + , Na + , K + ) yield MoS 2 or WS 2 flakes with uncontrolled phase mixing (2H/1T hybridization), severely limiting their functional reproducibility. Here, we demonstrate that phase-selective exfoliation for fabricating phase-pure 2H and 1T' TMD atomically thin nanosheets is both scalable and reliable. This process involves the electrochemical co-intercalation of Li-solvent (e.g., Li + -diethylene glycol dimethyl ether) and solvent-free Li-ion intercalation (e.g., propylene carbonate-based electrolyte) into 2H phase TMD crystal powders, followed by mild sonication and exfoliation. Quantitative modulation of the intercalation depth allows deterministic phase targeting, achieving monolayer yields exceeding 90% for 1T'-MoS 2 , WS 2 , and MoSe 2 , and bilayer/trilayer 2H-MoS 2 , WS 2 , and MoSe 2 with yields above 75%. Phase hybridization is further engineered at atomic precision, generating heterophase MoS 2 nanosheets with 1T' ratios tunable from 13% to 92% via electrosynthesis parameters. Further, our approach enables the mass production of high-phase-purity MoS 2 nanosheets on a hundred-gram scale via controlled charging of a LiFePO 4 ||MoS 2 pouch-cell configuration. This universal and selective synthesis of ultrathin TMD nanosheets presents opportunities to accelerate the exploration of electronic and photonic properties. Physical sciences/Materials science/Nanoscale materials/Two-dimensional materials Physical sciences/Materials science/Nanoscale materials/Electronic properties and materials Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Main Two-dimensional (2D) transition-metal dichalcogenides (TMDs), composed of layered materials bound by van der Waals interactions, have attracted substantial interest both in fundamental research and industrial applications 7-9 . In TMDs, phase is a key factor determining the properties, and hence functions 10,11 . Besides the conventional 2H phase, TMDs in octahedral (1T) or distorted octahedral (1T’) phases (Supplementary Fig. 1) display metallic and semi-metallic properties and have attracted growing attention for potential applications in next-generation electronics, catalysis and superconductivity devices 12-16 . However, the inability to controllably synthesize phase-pure 1T/1T’ monolayers or 2H few-layers from naturally abundant bulk precursors remains a critical bottleneck 17 . Current top-down strategies face intrinsic limitations: intercalation-based liquid exfoliation and mechanical exfoliation preserves the original 2H phase 18-20 , while conventional chemical/electrochemical Li-intercalation methods 21,22 induce uncontrolled electron doping that inevitably generates mixed-phase (1T’/2H) nanosheets (Fig. 1a) 23,24 . Although phase transitions during intercalation have been recognized since early work 25 , few methodology exists to selectively produce phase-pure TMD monolayer. This is because the electron doping required to stabilize the 2H-phase (demanding precise low-level electron injection) and 1T’-phase (requiring saturated electron doping) has not been quantitatively controlled—particularly at industrially relevant scales 26 . We address this challenge through solvent engineering-driven electrochemical intercalation (Fig. 1b). By systematically modulating Li + solvation chemistry, we achieve two distinct pathways: i) Solvent-free Li + intercalation under heated conditions accelerates Li + desolvation in propylene carbonate (PC), enabling full 2H→1T’ phase transformation through saturated electron injection to yield monolayer 1T’-TMDs (MoS 2 , WS 2 , MoSe 2 ). ii) Li + -diethylene glycol dimethyl ether (DEGDME) co-intercalation precisely caps electron injection below the phase transition threshold, preserving pristine few-layer 2H-TMDs (Fig.1b, see methods for details) from their bulk powders (particle size, purity and phase of the bulk material shown in Supplementary Fig. 2-6) guided by our in-situ XRD experiments and theoretical calculations. In addition, this principle further enables the creation of controlled 1T’/2H heterophase monolayers through voltage/temperature-tuned phase transitions. Next, we demonstrate scale-up viability using LiFePO 4 ||MoS 2 pouch-type batteries for 100-gram-level 1T’-MoS 2 monolayers production. For the application, the exfoliated 1T’ phase WS 2 showed record catalytic performance for NO 3 − reduction reaction (NO 3 − RR) with current densities high as 2.0 A cm −2 and NH 3 Faraday efficiency of 92%, initially showing the potential of pure-phase TMDs in scale-up application. Our method enables the selective phase synthesis of 2D TMDs, thereby further enriching their properties and extending their applications. The co-intercalation-driven exfoliated MoS 2 NSs dispersion exhibits a green color (Fig. 2a, inset), indicating partial visible light absorption, consistent with UV-vis spectral data (Fig. 2a and Supplementary Fig. 7a) that confirm the formation of semiconducting 2H-phase MoS 2 nanostructures 18 . Conversely, the solvent-free intercalated and exfoliated MoS 2 NSs dispersion exhibits a black color (Fig. 2a, inset), attributed to its complete and featureless visible-range absorption (Fig. 2a and Supplementary Fig. 7b), suggesting a phase transition toward metallic 1T/1T’ MoS 2 NSs. Only two dominant peaks (the in-plane phonon E 2g at 383.2 cm −1 and the out-of-plane phonon A 1g modes at 402.3 cm −1 ), corresponding to 2H-MoS 2 appear in the Raman spectroscopy of co-intercalation exfoliated MoS 2 NSs (Fig. 2b), indicating their 2H phase. In contrast, solvent-free exfoliated MoS 2 NSs display distinct J 1 , J 2 , and J 3 peaks in low-frequency regions along with near-absence of E 2g modes (Fig. 2b), confirming high-purity 1T’ phase formation 27 . In marked contrast, MoS 2 obtained by traditional electrochemical Li-ion intercalation exhibits both J-series peaks and E 2g peaks, indicative of a mixed phase with both 2H and 1T’ (Supplementary Fig. 8a) and is consistent with previously reported results 27,28 . The X-ray photoelectron spectroscopy (XPS) spectra of the exfoliated 1T’ MoS 2 exhibited two dominant Mo 3d peaks at ~228.2 eV (3d 5/2 ) and ~231.4 eV (3d 3/2 ), ~1.4 eV lower in binding energy than those of the 2H phase (229.6 eV and 232.8 eV, respectively), as shown in Fig. 2c and aligned with Ref. 12. By contrast, the mixed phases of 1T’ and 2H MoS 2 was produced by the traditional electrochemical Li-ion intercalation and exfoliation (Supplementary Fig. 8b) 15 . Furthermore, the atomic coordination is investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS spectra showed a lower chemical state in 1T’-MoS 2 NSs due to the enrichment of electrons on the surface (Supplementary Fig. 9a) 29 . The Mo K-edge EXAFS oscillation curves differ between 1T’- and 2H-MoS 2 (Supplementary Fig. 9b); its Fourier transform further reveals a shortened Mo-Mo bond in 1T’-MoS 2 , resulting from distorted octahedral coordination (Fig. 2d) 30 . The phase structures of exfoliated MoS 2 NSs were verified by aberration-corrected annular dark-field scanning transmission electron microscopy (ADF-STEM). Co-intercalation-exfoliated MoS₂ NSs exhibit a hexagonal lattice arrangement of Mo and S atoms in ADF-STEM imaging (Fig. 2e), confirming the 2H phase 31 . In contrast, solvent-free intercalation-exfoliated NSs display one-dimensional zigzag Mo atom chains (Fig. 2h), characteristic of the metastable 1T’ phase 32 . Furthermore, the corresponding fast Fourier transform (FFT, Fig. 2f and Fig. 2i) shows the diffraction characteristics of the 2H and 1T’ crystal structure of MoS 2 . The intensity profiles (Fig. 2g and Fig. 2j) show that the different Mo-Mo distances are 0.33 nm and 0.56 nm in 2H-MoS 2 , while 0.26 nm, 0.30 nm and 0.36 nm in 1T’-MoS 2 (the crystal model is shown in Supplementary Fig. 10). The selected area electron diffraction (SAED) pattern (Supplementary Fig. 11) further confirms the high crystallinity of the obtained 1T’- and 2H-MoS 2 NSs 33 . Atomic force microscopy (AFM) confirmed the successful preparation of large quantities of 2H- and 1T’-MoS 2 NSs (Fig. 2k, m), with mean thicknesses of 1.81 nm (bilayer) and 1.05 nm (monolayer) (Fig. 2l, n). The lateral sizes reached several micrometers for 2H-MoS 2 NSs and hundreds of nanometers for 1T’-MoS 2 NSs, confirming their bilayer and monolayer structures, respectively. Besides MoS 2 , phase-selective preparation of WS 2 and MoSe 2 were also successfully achieved by Li-solvent co-intercalation and solvent-free intercalation (Supplementary Fig. 12-15), and they were characterized in detail (see Extended Data Fig. 1 and Supplementary Fig. 16-21). Besides pure 1T’ monolayer and 2H bi-layer flakes, 1T’/2H heterophase NSs with 1T’-phase purity ranging from 13% to 92% can also be obtained by regulation of electrolytes, cut-off voltage, and reaction temperature. Using co-intercalation electrolytes, we obtained 2H-phase-dominated bi-layer MoS 2 (Extended Data Fig. 2a,b), and the 2H-phase ratio was adjustable from 55.1% to 100% by gradually increasing the cut-off voltage from 0.8 V to 1.1 V (Fig. 3a). For 1T’-phase-dominated heterophase NSs, decreasing cut-off voltage (from 0.9 V to 0.7 V) and increasing temperature (from 25 °C to 110 °C) can raise the 1T’-phase ratio from 70.1% to nearly 100% (Fig. 3b) and obtain nanosheets in single layers (Extended Data Fig. 2c,d). Heatmaps (Fig. 3c,d and see details in Supplementary Fig. 22) intuitively show the 1T’- or 2H-MoS 2 ratio and MoO x formation at the indicated cut-off voltage and temperature. It is worth noting that lowering the cut-off voltage and increasing the reaction temperature will increase the percentage of 1T’ phase (Fig. 3c), it may also result in the formation of MoO x (Fig. 3d), so the integrated modulation of the temperature and cut-off voltage in electrosynthesis is important for the formation of unoxidized 1T’-phase MoS 2 . Atomic-resolution STEM reveals that Mo and S atoms in 2H-phase MoS 2 are arranged hexagonally, with 2H regions embedded in the 1T’ phase in a triangular shape in both 2H-dominated and 1T’-dominated heterophase NSs (Fig. 3f-i). The discharge curves of MoS 2 ||Li cells reveal significant differences in the Li-ion intercalation process before exfoliation (Fig. 4a). In the previous Li-ion intercalation and exfoliation method using unmodulated traditional electrolyte, by setting the discharge cut-off voltage at 0.9 V (vs. Li + /Li), just after the state from MoS 2 to Li x MoS 2 located at ~1.1 V 34 . The Mo 3d XPS spectra shows the traditional electrochemical conditions make Li-intercalated MoS 2 under the mix of the 1T’ and 2H phases (Fig. 4b). In contrast, discharged in PC-based electrolyte at 110 ℃, MoS 2 exhibits enhanced electron injection (an increase of 0.85 e per unit) and forms a nearly pure 1T’ Li-intercalated MoS 2 (Fig. 4b). In the DEGDME-based electrolyte, the discharge curve mainly exhibits a diagonal shape rather than a plateau when cut-off at 0.9 V (Supplementary Fig. 23). By setting a higher cut-off voltage (1.1 V), we can make the electron injection lower by 1.25 e per unit when compared with the traditional electrolyte (Fig. 4a), thereby maintaining the 2H phase even in the intercalated MoS 2 (Fig. 4b). The formations of high-phase-purity 1T’- and 2H-MoS 2 induced by two different Li-intercalation methods were observed by electrochemical in-situ X-ray diffraction experiments (Fig. 4c,d and Supplementary Fig. 24). In DEGDME-based electrolyte, (002) diffraction peak at 14.2° corresponds to a lattice spacing of 0.62 nm in the bulk MoS 2 material (Fig. 4e) 35 , which gradually weakens during the discharge of the MoS 2 ||Li cell from the open-circuit potential to 1.1 V, indicating that interlayer spacing is enlarged during Li intercalation. (004) and (006) diffraction peaks belonging to bulk MoS 2 located at 28.6° and 43.7° gradually shifted to 12.2° and 28.6°, implying that the interlayer spacing expanded from 0.62 nm to 1.45 nm after Li-DEGDME co-intercalation (Fig. 4f). The Li + -DEGDME complex did not co-intercalate into each MoS 2 interlayer, as shown by the fact that the intercalated Li x MoS 2 still retained a lattice spacing of ~0.62 nm (Fig. 4f) and a weak (002) peak of 14.2° (Fig. 4c) at the end of discharging. The interlayer expansion is consistent with the thickness of the MoS 2 NSs after co-intercalation and exfoliation, shown by AFM characterizations with a high yield of few-layer MoS 2 NSs rather than monolayers (Fig. 2l). When MoS 2 was intercalated in PC-based electrolyte at 110 °C, the (002), (004), (006) and (008) 2H bulk diffraction peaks (located at 14.2°, 28.6°, 43.7° and 60.2°) disappear at a lithiation time of approximately 21 hours, and the (001) Li x MoS 2 appears (located at 14.0°) 36,37 , signifying that the 2H to 1T/1T’ phase transformation completes here. The starting point of the phase transition detected by in-situ Raman spectroscopy is at a discharge time of two hours (generation of the J 1 peak and the attenuation of the E 2g peak demonstrated in Supplementary Fig. 25), which is consistent with the result of in-situ XRD. At the end of the solvent-free intercalation, the Li x MoS 2 layer spacing was slightly enlarged from 0.62 nm to 0.63 nm (Fig. 4g). The phase transition behaviors during in-situ formation process can provide a basis for the phase-selective electrosynthesis of MoS 2 via phase transitions/retention strategies. To understand the synthesis process of phase-selective MoS 2 , we have performed theoretical explorations combining density functional theory (DFT) and molecular dynamics (MD) simulations. First of all, the thermodynamic properties of the 1T’ and 2H phase MoS 2 are demonstrated, where the 2H phase is more stable with 2.45 eV lower in formation energy (Extended Data Fig. 3). Based on the transition state (TS) search, the phase transition from 1T’ to 2H phase of MoS 2 requires an activation barrier of 3.03 eV, indicating that such a process needs the facilitation of heating during the synthesis. For the intercalation synthesis approach, the electrolyte molecules play a significant role due to the different affinity with Li-ions in the solution. Accordingly, the binding energy of DEGDME, DEC, PC, and EC with Li-ions are compared with varying coordination numbers (Supplementary Fig. 26). For all the electrolyte molecules, the binding energies gradually decrease with the increasing of coordination numbers, while the desolvation energies show a converse trend. In particular, DEGDME exhibits the strongest binding in Li + (DEGDME) 4 , leading to the largest desolvation energy costs. This reveals that the Li-ions in the DEGDME electrolyte are prone to forming stable complex structures, which causes the co-intercalation into the MoS 2 layers with low intercalation concentrations. In comparison, the binding between PC and Li + is very weak due to high energy costs for all coordination environments. The much lower desolvation barriers represent that the Li-ions migrate easily in the electrolyte as well as into the interlayers of MoS 2 during the synthesis condition, resulting in the largest intercalation concentration of ions to trigger the complete phase transition towards 1T’-MoS 2 . To further investigate the interactions between Li + and MoS 2 in various electrolytes, we performed molecular dynamics (MD) simulations. The migration activity of Li + towards the interlayer direction has been discussed through the mean square displacement (MSD), where Li + in PC electrolytes has the smallest MSD due to the strong interactions with MoS 2 within the interlayer (Supplementary Fig. 27). Moreover, we have compared the interaction energies between MoS 2 and electrolytes as well as the distortion ratios of MoS 2 (Supplementary Fig. 28). Notably, Li + has the strongest interactions with MoS 2 in the PC electrolyte with the lowest energy costs. This further realizes the highest concentrations of Li + in the interlayer of the MoS 2 to drive the phase transition into 1T’, which is further confirmed by the highest distortion ratios of the MoS 2 in the PC electrolyte after MD simulations. 100 gram-scale high-phase-purity 2H and 1T’-MoS 2 NSs were first prepared via DEGDME-based Li-solvent co-intercalation and PC-based Li-ion intercalation, respectively, and then combined with exfoliation approach (Fig. 5a). Here, we developed a full battery configuration (2H-MoS 2 ||LiFePO 4 ) where 2H-MoS 2 anodes and LiFePO 4 cathodes were premanufactured (Fig. 5b and Supplementary Fig. 29) with an industry-standard roll-to-roll process (Fig. 5a). The lithiation curves of LiFePO 4 ||Li and 2H-MoS 2 ||LiFePO 4 in the two kinds of phase-selective electrolytes were controlled (Supplementary Fig. 30). After intercalation in electrolytes, we put the MoS 2 anodes in water and ultrasonicated them to fully exfoliate the MoS 2 particles into 2D NSs. By centrifuging the resulting suspensions, we obtained ~10 L of 1T’-MoS 2 NSs (~10 g L −1 and ~98 % in 1T’ phase purity shown in Fig. 5c and Supplementary Fig. 31) from five soft pack batteries (~20 wt.% yield; Supplementary Fig. 30d). After exfoliation, the scaled-up production of 110.7 g of 1T’-MoS 2 NSs (Extended Data Fig. 4a) can be collected in solid state. Further, the MoS 2 NSs can be easily fabricated onto a flexible polyvinylidene difluoride (PVDF) substrate by vacuum filtration (Extended Data Fig. 4b-c) and cross-sectional SEM image (Extended Data Fig. 4d) reveals the typical lamellar and compact architecture of MoS 2 film. Fig. 5d shows comparisons of the 2H or 1T’ phase and scalability of co-intercalation/solvent-free intercalation and exfoliation for producing TMDs NSs with other exfoliation methods, such as Li-ion electrochemical exfoliation 34 , n-BuLi chemical exfoliation 23 , nap-Li chemical exfoliation 5 , solid lithiation for exfoliation 38 , solution-processable exfoliation 18 , mild electrochemical exfoliation 39 , solvent lithium intercalation for exfoliation 17 and solvent-assisted mechanical exfoliation 20 (details shown in Supplementary Table 1). Our method enables the batch preparation (hundred-gram range) of 1T’- and 2H- TMDs with high phase purity among all methods. High-phase-purity TMDs NSs synthesized via lithiation-exfoliation show promise for applications in catalysis, energy storage, and electronic devices due to their scalable production potential 43,44 . As demonstrated, 2H- and 1T’- MoS 2 , WS 2 and MoSe 2 NSs were used as electrocatalysts for NO 3 − reduction reaction (NO 3 − RR) (see detail in Methods and Supplementary Fig. 32-34). The 1T’ phase NSs (MoS 2 , WS 2 and MoSe 2 ) possessed higher reduction currents and Faraday efficiencies for NH 3 production comparing the pure 2H phase and the 1T’/2H mixed phase NSs (Fig. 5e-f and Supplementary Fig. 35) at high overpotentials (after −0.65 V). Among them, 1T’-WS 2 exhibits highest reduction current density up to ~2.0 A cm −2 with a Faraday efficiency of more than 92%, achieving a high NH 3 production rate of 143.4 mg h −1 cm −2 (Fig. 5g), which is still stable for 100 h of electrolysis at an industrial-grade current density of 1.0 A cm −2 (Extended Data Fig. 5a). Compared with previous works, it has obvious advantages in terms of reduction current and Faraday efficiency (Extended Data Fig. 5b and Supplementary Table 2). DFT calculations were used to explore the catalytic performances of different phases for nitrate reduction. We first compare the electronic structures of 1T’-WS 2 , 1T’-MoS 2 , and 1T’-MoSe 2 through the projected partial density of states (PDOS) (Supplementary Fig. 36). For the S-3p orbitals, a gradual upshifting is noted from WS 2 to MoS 2 . In MoSe 2 , the Se-4p orbitals become further closer to the Fermi level, inducing reduced overlapping between Mo-4d and Se-4p orbitals for electron transfer. Accordingly, the corresponding d-band and p-band centers of 1T’ phases are summarized (Supplementary Fig. 37). Notably, the d-band and p-band centers display a converse trend from WS 2 to MoSe 2 , supporting the reduced electroactivity due to the weakened p-d coupling with the enlarged mismatch of orbitals. These results confirm the highest electroactivity of 1T’-WS 2 for nitrate reduction. The PDOS are further compared to demonstrate the phase influences on the MoS 2 and WS 2 (Supplementary Fig. 38). It is apparent that the 2H-WS 2 and 2H-MoS 2 are semiconductors with evident band gaps for electron transfer while the 1T’-WS 2 and 1T’-MoS 2 exhibit metallic-like properties with much higher electron transfer efficiency, which guarantees the higher electroactivity of 1T’ phase for nitrate reduction. In the end, the reaction trends for nitrate reduction have been compared to 1T’-WS 2 and 2H-WS 2 (Supplementary Fig. 39). The 1T’ phase displays a stronger reaction trend than the 2H phase, where the rate-determining step (RDS) is the reduction of *NO 2 to *NO. The RDS barrier of the 1T’ phase is only 0.48 eV, which is only half that of the 2H phase (1.08 eV), supporting the improved nitrate reduction performance in 1T’-WS 2 . In summary, we have developed a general phase-controlled intercalation-exfoliation method for the hundred-gram synthesis of high-phase-purity TMDs nanosheets, offering a scalable alternative to traditional manufacturing methods. Enhanced NO 3 − RR performance of 1T’ TMDs suggested their potential applications as a high-performance catalyst. The intercalation mechanism allowed for the selective exfoliation of 1T’- and 2H- MoS 2 , WS 2 and MoSe 2 and the 1T’/2H heterophase monolayer or bi-layer by tuning electrochemical engineering. Our method provides straightforward access to pure 1T’, 2H, and heterophase NSs, facilitating the study of their unique properties. This advancement not only accelerates foundational research but also broadens their utility in fields including topological electronics, catalysis, energy storage, and flexible electronics. Online content Any methods, additional references, Nature Portfolio reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at https://doi.org/xxx. Methods Materials Lithium hexafluorophosphate (LiPF 6 , 99.9%), Propylene carbonate (PC, 99.9%), Diethylene glycol dimethyl ether (DEGDME, 99.9%), Dimethyl sulfoxide (DMSO, 99.9%), Li foils (99.9%), Copper foil (99.9%), N-methyl-2-pyrrolidone (NMP, 99%), Polyvinylidene difluoride (PVDF, 99%), Molybdenum disulfide (MoS 2 , 99%), Tungsten disulfide (WS 2 , 99%), and Molybdenum diselenide (MoSe 2 , 99%), Nafion 117-containing solution (5%), Ethanol (99%). The traditional electrolyte (1.0 M LiPF 6 in EC and DEC) was purchased from DodoChem Technology Co., Ltd. Electrolyte preparation Molecular sieves were used to dry the solvents before electrolyte preparation. LiPF 6 was dissolved in the solvent within an Argon-filled glove box (with H 2 O and O 2 level< 0.1 ppm) to prepare co-intercalation and solvent-free-intercalation electrolytes. Detailed compositions of the electrolytes used in this work are as follows: (i) for traditional Li-ion intercalation electrolyte: 1.0 M LiPF 6 in EC:DEC (v/v: 50:50); (ii) for 1T’- MoS 2 , WS 2 and MoSe 2 : 1.0 M LiPF 6 in PC; (iii) for 2H- MoS 2 : 1.0 M LiPF 6 in DEGDME; and (iv) for 2H- WS 2 and MoSe 2 : 1.0 M LiPF 6 in DMSO. Synthesis of 2H- and 1T’-TMDs NSs. Phase-pure 2H- and 1T’-TMDs NSs were synthesized via a controlled electrochemical Li + intercalation-exfoliation process. This method was carried out within a coin cell setup. The cell assembly steps were performed in an Argon-filled glovebox, employing 600-µm-thick Li foils as the lithium source and 40 μL of electrolyte per cell. TMD electrodes (MoS 2 , WS 2 , and MoSe 2 ) were fabricated by mixing bulk TMD powder (80 wt.%), carbon black (10 wt.%), and PVDF (10 wt.%) in NMP, while graphite anodes consisted of carbon black, PVDF, and graphite (1:1:8 mass ratio) coated on Cu foil and dried at 80°C under vacuum for 12 h. The key differences in the synthesis of 2H- and 1T’-TMDs NSs are associated with the cut-off voltage and temperature during the galvanostatic discharge. For the production of 2H-MoS 2 , WS 2 and MoSe 2 , these critical parameters were established 1.1 V, 0.9 V and 0.9 V, respectively, and all are at room temperature. Whereas for 1T’- MoS 2 , WS 2 and MoSe 2 , the temperatures were set at 110 °C, 150 °C and 110 °C, and all were discharged to 0.7 V (discharge curves are shown in Supplementary Fig. 12, 14). All battery tested with a current of 0.1 C (167.4 mAh g −1 for MoS 2 , 108.1 mAh g −1 for WS 2 and 105.6 mAh g −1 for MoSe 2 ). Additionally, 2H-TMDs NSs were prepared by sonication in ethanol: DI water =1:1, whereas 1T’ -TMDs NSs were fabricated through sonication in pre-oxygenated DI water. After sonication, the 2H and 1T’ suspensions were subjected to centrifugation and repeated washing before final redispersion in DI water for characterization and subsequent use. Material Characterizations ADF-STEM (JEOL ARM200F spherical aberration-corrected transmission electron microscope operated at 200kV). TEM (FEI talosf200s). XPS (Thermo Scientific K-Alpha Nexsa), STEM (JEOL-ARM300). Raman spectroscopy (WITec alpha 300 confocal Raman microscope, 532 nm). XAS (Beijing Synchrotron Radiation Facility, beamline 4B9A/1W2A, transmission mode). AFM (Dimension 3100, Veeco, CA). SEM (JSM-7600). UV-vis spectrophotometer (UH 4150 UV, Hitachi). ICP-MS (PE Nexion 2000). XRD (Bruker D8 diffractometer, Cu Kα radiation source). NO 3 – reduction reaction measurement The electrochemical NO 3 – reduction reactions were performed in a custom H-type cell, with a CHI660E workstation recording the electrochemical responses. The catholyte consisted of 1.0 M KNO 3 and 3 M KOH, while the anolyte contained 3 M KOH alone. In a typical three-electrode system, a Pt foil and a Hg/HgO electrode were used as the counter and reference electrodes, respectively. A Nafion 117 proton exchange membrane separated the anolyte and catholyte chambers. All potentials measured against Hg/HgO were converted to the RHE scale using the equation: E (vs. RHE) = E (vs. Hg/HgO) + 0.241 V + 0.0098×pH, with 85% iR compensation applied unless stated. Electrochemical impedance spectroscopy (EIS) was conducted over a frequency range of 0.1 Hz to 100 kHz. Synthesized 1T’- MoS 2 , WS 2 and MoSe 2 , 2H- MoS 2 , WS 2 and 1T’/2H mixed MoS 2 were directly used as the working electrode. For the working electrode preparation, TMDs inks were dispersed in alcohol with Nafion 117, sonicated for 40 min, and 160 µL of the catalyst ink was drop-casted onto a 0.5× 0.5 cm 2 carbon paper, achieving a loading of 0.3 mg cm –2 . Linear sweep voltammetry tests were recorded at 10 mV s –1 , while chronoamperometric tests were conducted at different potentials for 1.0 hours with a rotation rate of 300 rpm. Long-term stability was evaluated via chronopotentiometry tests at 1.0 A cm –2 . All the measurements were conducted at room temperature under ambient pressure. The concentration of NH 4 + –N was quantified using the Nessler’s reagent method. A fixed volume of catholyte was extracted and diluted to 10 mL for analysis within the instrument’s detection range. Potassium sodium tartrate solution (0.2 mL, 500 g L –1 ) and Nessler’s reagent (0.2 mL) were sequentially added, followed by thorough mixing. After a 20-minute equilibration period, absorbance was measured at 420 nm. A calibration curve was constructed using standard NH 4 Cl solutions with varying NH 4 + –N concentrations. Computational details In this study, we employed DFT calculations using the CASTEP package to investigate binding energies, desolvation energies, electronic structures, and reaction energy changes 45 . For all the calculations, we have chosen the generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) functionals to accurately describe the exchange-correlation energy 46-48 . Based on the ultrafine quality, the plane-wave basis cut-off energy has been set to 380 eV, and the ultrasoft pseudopotentials are applied for the calculation. Meanwhile, to balance precision and efficiency, the Broyden-Fletcher-Goldfarb-Shannon (BFGS) algorithm and coarse k-point sampling were implemented 49 . A 20 Å vacuum space along the z-axis ensured sufficient room for geometry relaxation. Convergence criteria included total energy differences below 5×10⁻ 5 eV/atom, Hellmann-Feynman forces under 0.001 eV/Å, and inter-ionic displacements limited to 0.005 Å. The MD simulations have been performed through the Forcite packages, where the electrolytes are constructed with Li + : electrolyte = 1:4. For each electrolyte model, there are four layers of MoS 2 . Equilibrated models underwent NVT-ensemble simulations at 298 K, controlled by the Universal forcefield and Nosé thermostat. A 1.0 ns simulation with 1.0 fs time steps (totaling 1×10 6 steps) ensured dynamic stability. Declarations Data availability : All data supporting the findings of this study are available in the paper and its Supplementary Information. Other raw data is available from the corresponding authors on request. Source data are provided with this paper. Acknowledgements : Z.Y. Zeng thanks the Young Collaborative Research Grant [Project No. C1003-23Y] and General Research Fund (GRF) [Project No. CityU11308923 and CityU 11309824] support from the Research Grants Council of the Hong Kong Special Administrative Region, China, the Applied Research Grant of City University of Hong Kong (project no of 9667247) and Chow Sang Sang Group Research Fund of City University of Hong Kong (project no of 9229123). Z.Y. Zeng also thanks the funding supported by the Seed Collaborative Research Fund Scheme of State Key Laboratory of Marine Pollution which receives regular research funding from the Innovation and Technology Commission (ITC) of the Hong Kong SAR Government. However, any opinions, findings, conclusions or recommendations expressed in this publication do not reflect the views of the Hong Kong SAR Government or the ITC. Author Contributions : Z. Zeng conceived and guided the project. H. Hu designed and performed the synthesis and characterizations of all the materials. H. Hu and Q. Zhang performed the device fabrication and performance test. D. Voiry, Y. Chai, R. Ye, B. Liu and X. Zhang helped to analyze the results. M. Sun and B. Huang conducted the DFT calculations and MD simulations. Z. Zhang performed the HAADF-STEM test of the samples. H. Hu, M. Sun, B. Liu, K.Loh, J. Li, and Z. Zeng drafted the paper. All authors checked the paper and agreed with its content. Competing interests : The authors declare no competing interests. Additional information Supplementary information The online version contains supplementary material available at https://doi.org/xxx. Correspondence and requests for materials should be addressed to Zhiyuan Zeng. Peer review information Nature thanks xxx and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Reprints and permissions information is available at http://www.nature.com/reprints. 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Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46 , 6671-6687, (1992). Head, J. D. & Zerner, M. C. A Broyden—Fletcher—Goldfarb—Shanno optimization procedure for molecular geometries. Chem. Phys. Lett. 122 , 264-270, (1985). Additional Declarations There is NO Competing Interest. Supplementary Files SupportingInformation.docx Supplementary Information ExtendedDataFig.docx Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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03:20:18","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6516593/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6516593/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":83264297,"identity":"6f568bdc-183d-4858-a68e-5f3cf02f91be","added_by":"auto","created_at":"2025-05-22 05:12:33","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":369993,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eSchematics for the phase-selective synthesis strategy.\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, TraditionalLi-ion intercalation by chemical/electrochemical methods. \u003cstrong\u003eb\u003c/strong\u003e, Phase-selective synthesis based on electrochemical Li-ion intercalation.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/12f8475875dcce64355519d9.png"},{"id":83264754,"identity":"73c31d40-02ff-4032-b5ab-420e3a768395","added_by":"auto","created_at":"2025-05-22 05:28:33","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":692360,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eStructural and optical characterization of exfoliated 1T’/2H MoS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e nanosheets (NSs).\u003c/strong\u003e \u003cstrong\u003ea\u003c/strong\u003e, Ultraviolet-visible absorption spectra of exfoliated 1T’ MoS\u003csub\u003e2\u003c/sub\u003e and 2H MoS\u003csub\u003e2\u003c/sub\u003e. Vertical dashed lines highlight four characteristic absorption peaks in the 2H phase spectrum. Photograph of exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs dispersed in aqueous ink solution, with the Tyndall effect observed in both phases (inset). a.u., arbitrary unit. \u003cstrong\u003eb\u003c/strong\u003e, Raman spectra of exfoliated 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs and 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs. \u003cstrong\u003ec\u003c/strong\u003e, XPS spectra of exfoliated 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs and 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs. The empty dots and the solid curves represent the experimental XPS data and the corresponding deconvoluted spectra, respectively. \u003cstrong\u003ed\u003c/strong\u003e, Fourier transform Mo K-edge EXAFS spectra in R space of the 1T’-MoS\u003csub\u003e2\u003c/sub\u003e and 2H-MoS\u003csub\u003e2\u003c/sub\u003e.\u003cstrong\u003e e\u003c/strong\u003e,\u003cstrong\u003eh\u003c/strong\u003e Atomic-resolution HAADF-STEM image of 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs (\u003cstrong\u003ee\u003c/strong\u003e) and 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs (\u003cstrong\u003eh\u003c/strong\u003e). \u003cstrong\u003ef\u003c/strong\u003e,\u003cstrong\u003ei\u003c/strong\u003e The corresponding fast Fourier transform pattern of 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs (\u003cstrong\u003ef\u003c/strong\u003e) and 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs (\u003cstrong\u003ei\u003c/strong\u003e). \u003cstrong\u003eg,j \u003c/strong\u003eIntensity profiles along the blue and red lines in (\u003cstrong\u003ee\u003c/strong\u003e) and (\u003cstrong\u003eh\u003c/strong\u003e), confirming the 2H phase (\u003cstrong\u003eg\u003c/strong\u003e) and 1T’ phase of the MoS\u003csub\u003e2 \u003c/sub\u003e(\u003cstrong\u003ej\u003c/strong\u003e). \u003cstrong\u003ek,m \u003c/strong\u003eAFM images of exfoliated 2H-MoS₂ NSs (\u003cstrong\u003ek\u003c/strong\u003e) and 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs (\u003cstrong\u003em\u003c/strong\u003e).\u003cstrong\u003e l,n \u003c/strong\u003eMeasured thicknesses, height profiles, and thickness distribution histograms of 2H-MoS₂ NSs (mean: 1.81 nm, s.d.: 0.31 nm, bi-layer yield: 81%) (\u003cstrong\u003el\u003c/strong\u003e) and 1T’-MoS\u003csub\u003e2\u003c/sub\u003e NSs (mean: 1.05 nm, s.d.: 0.10 nm, single layer yield: 92%) (\u003cstrong\u003en\u003c/strong\u003e).\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/22e12b2b845602c29ae7d411.png"},{"id":83264301,"identity":"89b41ce2-ce27-4f66-b4cb-d27c38bd07f4","added_by":"auto","created_at":"2025-05-22 05:12:33","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":631140,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eTailorable phase ratio of heterophase MoS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eNSs via electrosynthesis. a,b \u003c/strong\u003eHigh-resolution XPS Mo 3d spectra of exfoliated\u003cstrong\u003e \u003c/strong\u003e2H MoS\u003csub\u003e2\u003c/sub\u003e with phase retention synthesis process by increasing cut-off voltage from 0.8 V to 1.1 V in DEGDME-based electrolyte (\u003cstrong\u003ea\u003c/strong\u003e) and 1T’ MoS\u003csub\u003e2\u003c/sub\u003e with phase transformation synthesis process by decreasing cut-off voltage from 0.9 V to 0.7 V and raising temperature from 25 ℃ to 110 ℃ in PC-based electrolyte (\u003cstrong\u003eb\u003c/strong\u003e). \u003cstrong\u003ec\u003c/strong\u003e,\u003cstrong\u003ed\u003c/strong\u003e \u0026nbsp;Heatmaps of 1T’ MoS\u003csub\u003e2\u003c/sub\u003e percentage (\u003cstrong\u003ec\u003c/strong\u003e) and MoO\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003e percentage (\u003cstrong\u003ed\u003c/strong\u003e) for exfoliated 1T’ MoS\u003csub\u003e2\u003c/sub\u003e NSs\u0026nbsp;with different synthesis conditions of cut-off voltage and temperature (OCV stands for open circuit voltage, i.e., tested when the battery is assembled but not discharged). \u003cstrong\u003ef\u003c/strong\u003e-\u003cstrong\u003ei\u003c/strong\u003e, Atomic-resolution ADF-STEM images showing the detailed configurations of four ratios of 1T’ MoS\u003csub\u003e2\u003c/sub\u003e in MoS\u003csub\u003e2 \u003c/sub\u003eNSs. The green area shows the 2H MoS\u003csub\u003e2\u003c/sub\u003e with a triangular shape embedded in the 1T’ MoS\u003csub\u003e2\u003c/sub\u003e with 1T’ ratio of 13% (\u003cstrong\u003ef\u003c/strong\u003e), 45% (\u003cstrong\u003eg\u003c/strong\u003e), 78% (\u003cstrong\u003eh\u003c/strong\u003e) and 92% (\u003cstrong\u003ei\u003c/strong\u003e). All panels share the same scale bar.\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/84fe0cf5314522b761fb5a45.png"},{"id":83264879,"identity":"bd90ab0b-33f7-42b3-adcb-61fdd53352c8","added_by":"auto","created_at":"2025-05-22 05:36:33","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":693052,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eIn-situ\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e formation of 1T\u003c/strong\u003e’\u003cstrong\u003e/2H MoS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2 \u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003eby quantitative Li-ion intercalation. a\u003c/strong\u003e, Electrochemical discharge voltage profiles of MoS\u003csub\u003e2\u003c/sub\u003e versus Li\u003csup\u003e+\u003c/sup\u003e/Li with traditional electrolyte (cut-off at 0.9 V), DEGDME-based electrolyte (cut-off at 1.1 V) and PC-based electrolyte (cut-off at 0.7 V, 110 °C).\u0026nbsp; \u003cstrong\u003eb\u003c/strong\u003e, Mo 3d XPS spectra of intercalated Li\u003csub\u003e\u003cem\u003ex\u003c/em\u003e\u003c/sub\u003eMoS\u003csub\u003e2\u003c/sub\u003e formation in three kinds of electrolytes.\u0026nbsp; \u003cstrong\u003ec\u003c/strong\u003e,\u003cstrong\u003ed\u003c/strong\u003e \u003cem\u003eIn-situ\u003c/em\u003e XRD of 2H-MoS\u003csub\u003e2\u003c/sub\u003e powder electrodes on discharging in DEGDME-based electrolyte (\u003cstrong\u003ec\u003c/strong\u003e) and PC-based electrolyte (\u003cstrong\u003ed\u003c/strong\u003e) and the corresponding electrochemical profiles. \u003cstrong\u003ee\u003c/strong\u003e-\u003cstrong\u003eg\u003c/strong\u003e Cross-sectional HRTEM images of multilayer bulk MoS\u003csub\u003e2 \u003c/sub\u003e(\u003cstrong\u003ee\u003c/strong\u003e), DEGDME-based electrolyte intercalated MoS\u003csub\u003e2\u003c/sub\u003e (\u003cstrong\u003ef\u003c/strong\u003e) and PC-based electrolyte intercalated MoS\u003csub\u003e2 \u003c/sub\u003e(\u003cstrong\u003eg\u003c/strong\u003e). All panels share the same scale bar.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/9f7f386c52521ccef80ee99d.png"},{"id":83264299,"identity":"43c0ae06-8563-4e15-a07c-77893a53a3ef","added_by":"auto","created_at":"2025-05-22 05:12:33","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":695596,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScale-up preparation and electrochemical NO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e−\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e reduction reaction (NO\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e\u003csup\u003e\u003cstrong\u003e−\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003eRR) performance of high-phase-purity MoS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e, WS\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e and MoSe\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e\u003cstrong\u003e. a\u003c/strong\u003e, 100 g-scale 2H/1T’ MoS\u003csub\u003e2\u003c/sub\u003e nanosheets fabricated by conducting charge process for LiFePO\u003csub\u003e4\u003c/sub\u003e cathode pouch-type battery and then exfoliating the lithiated TMDs anode in DI water. \u003cstrong\u003eb\u003c/strong\u003e-\u003cstrong\u003ec\u003c/strong\u003e, Digital photographs of pouch-type battery and clamps for pressing pouch cell (\u003cstrong\u003eb\u003c/strong\u003e), ~10 L of highly concentrated 2H-MoS\u003csub\u003e2\u003c/sub\u003e (dark green color) and 1T’- MoS\u003csub\u003e2\u003c/sub\u003e (dark black color) ink solutions (concentration: ~10 g L\u003csup\u003e−1\u003c/sup\u003e) (\u003cstrong\u003ec\u003c/strong\u003e). \u003cstrong\u003ed\u003c/strong\u003e, Phase purity versus production scale of TMDs nanosheets prepared by different methods, including Li-ion electrochemical exfoliation\u003csup\u003e34\u003c/sup\u003e, n-BuLi chemical exfoliation\u003csup\u003e23\u003c/sup\u003e, nap-Li chemical exfoliation\u003csup\u003e5\u003c/sup\u003e, solid lithiation for exfoliation\u003csup\u003e38\u003c/sup\u003e, \u0026nbsp;solution-processable exfoliation\u003csup\u003e18\u003c/sup\u003e, mild electrochemical exfoliation\u003csup\u003e39\u003c/sup\u003e, solvent lithium intercalation for exfoliation\u003csup\u003e17\u003c/sup\u003e, solvent-assisted mechanical exfoliation\u003csup\u003e20\u003c/sup\u003e, solid-state ball milling exfoliation\u003csup\u003e40\u003c/sup\u003e, redox liquid phase exfoliation\u003csup\u003e41\u003c/sup\u003e, and intermediate assisted grinding exfoliation\u003csup\u003e42\u003c/sup\u003e. \u003cstrong\u003ee\u003c/strong\u003e-\u003cstrong\u003ef\u003c/strong\u003e, \u003cem\u003eI–V \u003c/em\u003eplots (\u003cstrong\u003ee\u003c/strong\u003e) and the corresponding NH\u003csub\u003e3\u003c/sub\u003e\u0026nbsp;FEs (\u003cstrong\u003ef\u003c/strong\u003e) measured in a 1 M KNO\u003csub\u003e3\u003c/sub\u003e electrolyte within a potential window of −0.2 V to −0.8 V versus RHE. Error bars represent standard deviations from three replicates, with center values reflecting average data. \u003cstrong\u003eg\u003c/strong\u003e, The corresponding NH\u003csub\u003e3\u003c/sub\u003e\u0026nbsp;production rate and partial current density of 1T’-MoS\u003csub\u003e2\u003c/sub\u003e and 1T’-WS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/e0f93acfb0b2238acfac5821.png"},{"id":100373421,"identity":"01ffa24f-5bb8-4163-99c2-e7b44dcfac74","added_by":"auto","created_at":"2026-01-16 08:14:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4255976,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/58140dc5-ef81-4cc8-af7f-e820b955e3f3.pdf"},{"id":83264302,"identity":"69b9d3c1-7e99-4002-a002-0df7ec847fe9","added_by":"auto","created_at":"2025-05-22 05:12:33","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":13591230,"visible":true,"origin":"","legend":"Supplementary Information","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/6f9ec01f79dcbc3809e5b624.docx"},{"id":83264304,"identity":"6e904d0c-36e2-4e1d-bf91-c158dfd01f0e","added_by":"auto","created_at":"2025-05-22 05:12:33","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":3214993,"visible":true,"origin":"","legend":"","description":"","filename":"ExtendedDataFig.docx","url":"https://assets-eu.researchsquare.com/files/rs-6516593/v1/e9fd348e4842aff851b9ad63.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Electrochemical engineering for phase-controlled exfoliation of transition metal dichalcogenides","fulltext":[{"header":"Main","content":"\u003cp\u003eTwo-dimensional (2D) transition-metal dichalcogenides (TMDs), composed of layered materials bound by van der Waals interactions, have attracted substantial interest both in fundamental research and industrial applications\u003csup\u003e7-9\u003c/sup\u003e. In TMDs, phase is a key factor determining the properties, and hence functions\u003csup\u003e10,11\u003c/sup\u003e. Besides the conventional 2H phase, TMDs in octahedral (1T) or distorted octahedral (1T\u0026rsquo;) phases (Supplementary Fig. 1) display metallic and semi-metallic properties and have attracted growing attention for potential applications in next-generation electronics, catalysis and superconductivity devices\u003csup\u003e12-16\u003c/sup\u003e. However, the inability to controllably synthesize phase-pure 1T/1T\u0026rsquo; monolayers or 2H few-layers from naturally abundant bulk precursors remains a critical bottleneck\u003csup\u003e17\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eCurrent top-down strategies face intrinsic limitations: intercalation-based liquid exfoliation and mechanical exfoliation preserves the original 2H phase\u003csup\u003e18-20\u003c/sup\u003e, while conventional chemical/electrochemical Li-intercalation methods\u003csup\u003e21,22\u003c/sup\u003e induce uncontrolled electron doping that inevitably generates mixed-phase (1T\u0026rsquo;/2H) nanosheets (Fig. 1a)\u003csup\u003e23,24\u003c/sup\u003e. Although phase transitions during intercalation have been recognized since early work\u003csup\u003e25\u003c/sup\u003e, few methodology exists to selectively produce phase-pure TMD monolayer. This is because the electron doping required to stabilize the 2H-phase (demanding precise low-level electron injection) and 1T\u0026rsquo;-phase (requiring saturated electron doping) has not been quantitatively controlled\u0026mdash;particularly at industrially relevant scales\u003csup\u003e26\u003c/sup\u003e.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWe address this challenge through solvent engineering-driven electrochemical intercalation (Fig. 1b). By systematically modulating Li\u003csup\u003e+\u003c/sup\u003e solvation chemistry, we achieve two distinct pathways: i) Solvent-free Li\u003csup\u003e+\u003c/sup\u003e intercalation under heated conditions accelerates Li\u003csup\u003e+\u003c/sup\u003e desolvation in propylene carbonate (PC), enabling full 2H\u0026rarr;1T\u0026rsquo; phase transformation through saturated electron injection to yield monolayer 1T\u0026rsquo;-TMDs (MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e, MoSe\u003csub\u003e2\u003c/sub\u003e). ii) Li\u003csup\u003e+\u003c/sup\u003e-diethylene glycol dimethyl ether (DEGDME) co-intercalation precisely caps electron injection below the phase transition threshold, preserving pristine few-layer 2H-TMDs (Fig.1b, see methods for details) from their bulk powders (particle size, purity and phase of the bulk material shown in Supplementary Fig. 2-6) guided by our \u003cem\u003ein-situ\u003c/em\u003e XRD experiments and theoretical calculations. In addition, this principle further enables the creation of controlled 1T\u0026rsquo;/2H heterophase monolayers through voltage/temperature-tuned phase transitions.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eNext, we demonstrate scale-up viability using LiFePO\u003csub\u003e4\u003c/sub\u003e||MoS\u003csub\u003e2\u003c/sub\u003e pouch-type batteries for 100-gram-level 1T\u0026rsquo;-MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003emonolayers production. For the application, the exfoliated 1T\u0026rsquo; phase WS\u003csub\u003e2\u003c/sub\u003e showed record catalytic performance for NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e reduction reaction (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003eRR) with current densities high as 2.0 A cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e and NH\u003csub\u003e3\u003c/sub\u003e Faraday efficiency of 92%, initially showing the potential of pure-phase TMDs in scale-up application. Our method enables the selective phase synthesis of 2D TMDs, thereby further enriching their properties and extending their applications.\u003c/p\u003e\n\u003cp\u003eThe co-intercalation-driven exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs dispersion exhibits a green color (Fig. 2a, inset), indicating partial visible light absorption, consistent with UV-vis spectral data (Fig. 2a and Supplementary Fig. 7a) that confirm the formation of semiconducting 2H-phase MoS\u003csub\u003e2\u003c/sub\u003e nanostructures\u003csup\u003e18\u003c/sup\u003e.\u0026nbsp;Conversely, the solvent-free intercalated and exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs dispersion exhibits a black color\u0026nbsp;(Fig.\u0026nbsp;2a, inset), attributed to its complete and featureless visible-range absorption (Fig. 2a and Supplementary Fig. 7b), suggesting a phase transition toward metallic 1T/1T\u0026rsquo; MoS\u003csub\u003e2\u003c/sub\u003e NSs. Only two dominant peaks (the in-plane phonon E\u003csub\u003e2g\u003c/sub\u003e at 383.2\u0026thinsp;cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e and the out-of-plane phonon A\u003csub\u003e1g\u003c/sub\u003e modes at 402.3\u0026thinsp;cm\u003csup\u003e\u0026minus;1\u003c/sup\u003e), corresponding to 2H-MoS\u003csub\u003e2\u003c/sub\u003e appear in the Raman spectroscopy of co-intercalation exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs (Fig. 2b), indicating their 2H phase. In contrast, solvent-free exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs display distinct J\u003csub\u003e1\u003c/sub\u003e, J\u003csub\u003e2\u003c/sub\u003e, and J\u003csub\u003e3\u003c/sub\u003e peaks in low-frequency regions along with near-absence of E\u003csub\u003e2g\u003c/sub\u003e modes (Fig. 2b), confirming high-purity 1T\u0026rsquo; phase formation\u003csup\u003e27\u003c/sup\u003e. In marked contrast, MoS\u003csub\u003e2\u003c/sub\u003e obtained by traditional electrochemical Li-ion intercalation exhibits both J-series peaks and E\u003csub\u003e2g\u003c/sub\u003e peaks, indicative of a mixed phase with both 2H and 1T\u0026rsquo; (Supplementary Fig. 8a) and is consistent with previously reported results\u003csup\u003e27,28\u003c/sup\u003e. The X-ray photoelectron spectroscopy (XPS) spectra of the exfoliated 1T\u0026rsquo; MoS\u003csub\u003e2\u003c/sub\u003e exhibited two dominant Mo 3d peaks at ~228.2 eV (3d\u003csub\u003e5/2\u003c/sub\u003e) and ~231.4 eV (3d\u003csub\u003e3/2\u003c/sub\u003e), ~1.4 eV lower in binding energy than those of the 2H phase (229.6 eV and 232.8 eV, respectively), as shown in Fig. 2c and aligned with Ref. 12. By contrast, the mixed phases of 1T\u0026rsquo; and 2H\u0026nbsp;MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ewas produced by the traditional electrochemical Li-ion intercalation and exfoliation (Supplementary Fig. 8b)\u003csup\u003e15\u003c/sup\u003e. Furthermore, the atomic coordination is investigated by extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS spectra showed a lower chemical state in 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e NSs due to the enrichment of electrons on the surface (Supplementary Fig. 9a)\u003csup\u003e29\u003c/sup\u003e. The Mo K-edge EXAFS oscillation curves differ between 1T\u0026rsquo;- and 2H-MoS\u003csub\u003e2\u003c/sub\u003e (Supplementary Fig. 9b); its Fourier transform further reveals a shortened Mo-Mo bond in 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e, resulting from distorted octahedral coordination (Fig. 2d)\u003csup\u003e30\u003c/sup\u003e. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe phase structures of exfoliated MoS\u003csub\u003e2\u003c/sub\u003e NSs were verified by aberration-corrected annular dark-field scanning transmission electron microscopy (ADF-STEM). Co-intercalation-exfoliated MoS₂ NSs exhibit a hexagonal lattice arrangement of Mo and S atoms in ADF-STEM imaging (Fig. 2e), confirming the 2H phase\u003csup\u003e31\u003c/sup\u003e. In contrast, solvent-free intercalation-exfoliated NSs display one-dimensional zigzag Mo atom chains (Fig. 2h), characteristic of the metastable 1T\u0026rsquo; phase\u003csup\u003e32\u003c/sup\u003e. Furthermore, the corresponding fast Fourier transform (FFT, Fig. \u0026nbsp;2f and Fig. 2i) shows the diffraction characteristics of the 2H and 1T\u0026rsquo; crystal structure of MoS\u003csub\u003e2\u003c/sub\u003e. The intensity profiles (Fig. 2g and Fig. 2j) show that the different Mo-Mo distances are 0.33 nm and 0.56 nm in 2H-MoS\u003csub\u003e2\u003c/sub\u003e, while 0.26 nm, 0.30 nm and 0.36 nm in 1T\u0026rsquo;-MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(the crystal model is shown in Supplementary Fig. 10). The selected area electron diffraction (SAED) pattern (Supplementary Fig. 11) further confirms the high crystallinity of the obtained 1T\u0026rsquo;- and 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs\u003csup\u003e33\u003c/sup\u003e. Atomic force microscopy (AFM) confirmed the successful preparation of large quantities of 2H- and 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e NSs (Fig. 2k, m), with mean thicknesses of 1.81 nm (bilayer) and 1.05 nm (monolayer) (Fig. 2l, n). The lateral sizes reached several micrometers for 2H-MoS\u003csub\u003e2\u003c/sub\u003e NSs and hundreds of nanometers for 1T\u0026rsquo;-MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eNSs, confirming their bilayer and monolayer structures, respectively.\u0026nbsp;Besides MoS\u003csub\u003e2\u003c/sub\u003e, phase-selective preparation of WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e were also successfully achieved by Li-solvent co-intercalation and solvent-free intercalation (Supplementary Fig. 12-15), and they were characterized in detail (see Extended Data Fig. 1 and Supplementary Fig. 16-21).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBesides pure 1T\u0026rsquo; monolayer and 2H bi-layer flakes, 1T\u0026rsquo;/2H heterophase NSs with 1T\u0026rsquo;-phase purity ranging from 13% to 92% can also be obtained by regulation of electrolytes, cut-off voltage, and reaction temperature. Using co-intercalation electrolytes, we obtained 2H-phase-dominated bi-layer MoS\u003csub\u003e2\u003c/sub\u003e (Extended Data Fig. 2a,b), and the 2H-phase ratio was adjustable from 55.1% to 100% by gradually increasing the cut-off voltage from 0.8 V to 1.1 V (Fig. 3a). For 1T\u0026rsquo;-phase-dominated heterophase NSs, decreasing cut-off voltage (from 0.9 V to 0.7 V) and increasing temperature (from 25 \u0026deg;C to 110 \u0026deg;C) can raise the 1T\u0026rsquo;-phase ratio from 70.1% to nearly 100% (Fig. 3b) and obtain nanosheets in single layers (Extended Data Fig. 2c,d). Heatmaps (Fig. 3c,d and see details in Supplementary Fig. 22) intuitively show the 1T\u0026rsquo;- or 2H-MoS\u003csub\u003e2\u003c/sub\u003e ratio and MoO\u003cem\u003e\u003csub\u003ex\u003c/sub\u003e\u003c/em\u003e formation at the indicated cut-off voltage and temperature. It is worth noting that lowering the cut-off voltage and increasing the reaction temperature will increase the percentage of 1T\u0026rsquo; phase (Fig. 3c), it may also result in the formation of MoO\u003cem\u003e\u003csub\u003ex\u003c/sub\u003e\u003c/em\u003e (Fig. 3d), so the integrated modulation of the temperature and cut-off voltage in electrosynthesis is important for the formation of unoxidized 1T\u0026rsquo;-phase MoS\u003csub\u003e2\u003c/sub\u003e. Atomic-resolution STEM reveals that Mo and S atoms in 2H-phase MoS\u003csub\u003e2\u003c/sub\u003e are arranged hexagonally, with 2H regions embedded in the 1T\u0026rsquo; phase in a triangular shape in both 2H-dominated and 1T\u0026rsquo;-dominated heterophase NSs (Fig. 3f-i).\u003c/p\u003e\n\u003cp\u003eThe discharge curves of MoS\u003csub\u003e2\u003c/sub\u003e||Li cells reveal significant differences in the Li-ion intercalation process before exfoliation (Fig. 4a). In the previous Li-ion intercalation and exfoliation method using unmodulated traditional electrolyte, by setting the discharge cut-off voltage at 0.9 V (vs. Li\u003csup\u003e+\u003c/sup\u003e/Li), just after the state from MoS\u003csub\u003e2\u003c/sub\u003e to Li\u003csub\u003ex\u003c/sub\u003eMoS\u003csub\u003e2\u003c/sub\u003e located at ~1.1 V\u003csup\u003e34\u003c/sup\u003e. The Mo 3d XPS spectra shows the traditional electrochemical conditions make Li-intercalated MoS\u003csub\u003e2\u003c/sub\u003e under the mix of the 1T\u0026rsquo; and 2H phases (Fig. 4b). In contrast, discharged in PC-based electrolyte at 110 ℃, MoS\u003csub\u003e2\u003c/sub\u003e exhibits enhanced electron injection (an increase of 0.85 e per unit) and forms a nearly pure 1T\u0026rsquo; Li-intercalated MoS\u003csub\u003e2\u003c/sub\u003e (Fig. 4b). In the DEGDME-based electrolyte, the discharge curve mainly exhibits a diagonal shape rather than a plateau when cut-off at 0.9 V (Supplementary Fig. 23). By setting a higher cut-off voltage (1.1 V), we can make the electron injection lower by 1.25 e per unit when compared with the traditional electrolyte (Fig. 4a), thereby maintaining the 2H phase even in the intercalated MoS\u003csub\u003e2\u003c/sub\u003e (Fig. 4b).\u003c/p\u003e\n\u003cp\u003eThe formations of high-phase-purity 1T\u0026rsquo;- and 2H-MoS\u003csub\u003e2\u003c/sub\u003e\u003csub\u003e\u0026nbsp;\u003c/sub\u003einduced by two different Li-intercalation methods were observed by electrochemical \u003cem\u003ein-situ\u003c/em\u003e X-ray diffraction experiments (Fig. 4c,d and Supplementary Fig. 24). In DEGDME-based electrolyte, (002) diffraction peak at 14.2\u0026deg; corresponds to a lattice spacing of 0.62 nm in the bulk MoS\u003csub\u003e2\u003c/sub\u003e material (Fig. 4e)\u003csup\u003e35\u003c/sup\u003e, which gradually weakens during the discharge of the MoS\u003csub\u003e2\u003c/sub\u003e||Li cell from the open-circuit potential to 1.1 V, indicating that\u0026nbsp;interlayer spacing\u0026nbsp;is enlarged during Li intercalation. (004) and (006)\u0026nbsp;diffraction\u0026nbsp;peaks belonging to bulk MoS\u003csub\u003e2\u003c/sub\u003e located at 28.6\u0026deg; and 43.7\u0026deg; gradually shifted to 12.2\u0026deg; and 28.6\u0026deg;, implying that the interlayer spacing expanded from 0.62 nm to 1.45 nm after Li-DEGDME co-intercalation (Fig. 4f). The Li\u003csup\u003e+\u003c/sup\u003e-DEGDME complex did not co-intercalate into each MoS\u003csub\u003e2\u003c/sub\u003e interlayer, as shown by the fact that the intercalated Li\u003cem\u003e\u003csub\u003ex\u003c/sub\u003e\u003c/em\u003eMoS\u003csub\u003e2\u003c/sub\u003e still retained a lattice spacing of ~0.62 nm (Fig. 4f) and a weak (002) peak of 14.2\u0026deg; (Fig. 4c) at the end of discharging. The interlayer expansion is consistent with the thickness of the MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eNSs\u0026nbsp;after\u0026nbsp;co-intercalation\u0026nbsp;and exfoliation,\u0026nbsp;shown by\u0026nbsp;AFM\u0026nbsp;characterizations\u0026nbsp;with a high yield of few-layer MoS\u003csub\u003e2\u003c/sub\u003e NSs rather than monolayers (Fig. 2l).\u003c/p\u003e\n\u003cp\u003eWhen MoS\u003csub\u003e2\u003c/sub\u003e was intercalated in PC-based electrolyte at 110 \u0026deg;C, the (002), (004), (006) and (008) 2H bulk diffraction peaks (located at 14.2\u0026deg;, 28.6\u0026deg;, 43.7\u0026deg; and 60.2\u0026deg;) disappear at a lithiation time of approximately 21 hours, and the (001) Li\u003cem\u003e\u003csub\u003ex\u003c/sub\u003e\u003c/em\u003eMoS\u003csub\u003e2\u003c/sub\u003e appears (located at 14.0\u0026deg;)\u003csup\u003e36,37\u003c/sup\u003e, signifying that the 2H to 1T/1T\u0026rsquo; phase transformation completes here. The starting point of the phase transition detected by \u003cem\u003ein-situ\u003c/em\u003e Raman spectroscopy is at a discharge time of two hours (generation of the J\u003csub\u003e1\u003c/sub\u003e peak and the attenuation of the E\u003csub\u003e2g\u003c/sub\u003e peak demonstrated in Supplementary Fig. 25), which is consistent with the result of \u003cem\u003ein-situ\u003c/em\u003e XRD. At the end of the solvent-free intercalation, the Li\u003cem\u003e\u003csub\u003ex\u003c/sub\u003e\u003c/em\u003eMoS\u003csub\u003e2\u003c/sub\u003e layer spacing was slightly enlarged from 0.62 nm to 0.63 nm (Fig. 4g). The phase transition behaviors during \u003cem\u003ein-situ\u003c/em\u003e formation process can provide a basis for the phase-selective electrosynthesis of MoS\u003csub\u003e2\u003c/sub\u003e via phase transitions/retention strategies.\u003c/p\u003e\n\u003cp\u003eTo understand the synthesis process of phase-selective MoS\u003csub\u003e2\u003c/sub\u003e, we have performed theoretical explorations combining density functional theory (DFT) and molecular dynamics (MD) simulations. First of all,\u0026nbsp;the thermodynamic properties of the 1T\u0026rsquo; and 2H phase MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eare demonstrated, where the 2H phase is more stable with 2.45 eV lower in formation energy (Extended Data Fig. 3). Based on the transition state (TS) search, the phase transition from 1T\u0026rsquo; to 2H phase of MoS\u003csub\u003e2\u003c/sub\u003e requires an activation barrier of 3.03 eV, indicating that such a process needs the facilitation of heating during the synthesis. For the intercalation synthesis approach, the electrolyte molecules play a significant role due to the different affinity with Li-ions in the solution. Accordingly, the binding energy of DEGDME, DEC, PC, and EC with Li-ions are compared with varying coordination numbers (Supplementary Fig.\u0026nbsp;26). For all the electrolyte molecules, the binding energies gradually decrease with the increasing of coordination numbers, while the desolvation energies show a converse trend. In particular, DEGDME exhibits the strongest binding in Li\u003csup\u003e+\u003c/sup\u003e(DEGDME)\u003csub\u003e4\u003c/sub\u003e, leading to the largest desolvation energy costs. This reveals that the Li-ions in the DEGDME electrolyte are prone to forming stable complex structures, which causes the co-intercalation into the MoS\u003csub\u003e2\u003c/sub\u003e layers with low intercalation concentrations.\u0026nbsp;In comparison, the binding between PC and Li\u003csup\u003e+\u003c/sup\u003e is very weak due to\u0026nbsp;high\u0026nbsp;energy costs for all coordination environments. The much lower desolvation barriers represent that the\u0026nbsp;Li-ions\u0026nbsp;migrate easily in the electrolyte as well as into the interlayers of MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eduring the synthesis condition, resulting in the largest intercalation\u0026nbsp;concentration of ions to trigger the complete phase transition towards 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eTo further investigate the interactions between Li\u003csup\u003e+\u003c/sup\u003e and MoS\u003csub\u003e2\u003c/sub\u003e in various electrolytes, we performed molecular dynamics (MD) simulations. The migration activity of Li\u003csup\u003e+\u003c/sup\u003e towards the interlayer direction has been discussed through the mean square displacement (MSD), where Li\u003csup\u003e+\u003c/sup\u003e in PC electrolytes has the smallest MSD due to the strong interactions with MoS\u003csub\u003e2\u003c/sub\u003e within the interlayer (Supplementary Fig. 27). Moreover, we have compared the interaction energies between MoS\u003csub\u003e2\u003c/sub\u003e and electrolytes as well as the distortion ratios of MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(Supplementary Fig.\u0026nbsp;28). Notably,\u0026nbsp;Li\u003csup\u003e+\u0026nbsp;\u003c/sup\u003ehas the strongest interactions with MoS\u003csub\u003e2\u003c/sub\u003e in the PC electrolyte with the lowest energy costs. This further realizes the highest concentrations of Li\u003csup\u003e+\u003c/sup\u003e in the interlayer of the MoS\u003csub\u003e2\u003c/sub\u003e to drive the phase transition into 1T\u0026rsquo;, which is further confirmed by the highest distortion ratios of the MoS\u003csub\u003e2\u003c/sub\u003e in the PC electrolyte after MD simulations.\u003c/p\u003e\n\u003cp\u003e100 gram-scale high-phase-purity 2H and 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e NSs were first prepared via DEGDME-based Li-solvent co-intercalation and PC-based Li-ion intercalation, respectively, and then combined with exfoliation approach (Fig. 5a). Here, we developed a full battery configuration (2H-MoS\u003csub\u003e2\u003c/sub\u003e||LiFePO\u003csub\u003e4\u003c/sub\u003e)\u0026nbsp;where\u0026nbsp;2H-MoS\u003csub\u003e2\u003c/sub\u003e anodes\u0026nbsp;and LiFePO\u003csub\u003e4\u003c/sub\u003e cathodes were premanufactured\u0026nbsp;(Fig. 5b\u0026nbsp;and Supplementary Fig.\u0026nbsp;29)\u0026nbsp;with an industry-standard\u0026nbsp;roll-to-roll process (Fig.\u0026nbsp;5a). The lithiation\u0026nbsp;curves\u0026nbsp;of LiFePO\u003csub\u003e4\u003c/sub\u003e||Li and 2H-MoS\u003csub\u003e2\u003c/sub\u003e||LiFePO\u003csub\u003e4\u003c/sub\u003e in the two\u0026nbsp;kinds of phase-selective\u0026nbsp;electrolytes were\u0026nbsp;controlled (Supplementary Fig.\u0026nbsp;30). After intercalation in electrolytes, we put the\u0026nbsp;MoS\u003csub\u003e2\u003c/sub\u003e anodes in water and ultrasonicated them to fully exfoliate the MoS\u003csub\u003e2\u003c/sub\u003e particles into 2D\u0026nbsp;NSs. By centrifuging the resulting suspensions, we obtained ~10 L\u0026nbsp;of 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e NSs\u0026nbsp;(~10 g L\u003csup\u003e\u0026minus;1\u003c/sup\u003e and\u0026nbsp;~98\u0026thinsp;% in 1T\u0026rsquo;\u0026nbsp;phase purity\u0026nbsp;shown in\u0026nbsp;Fig.\u0026nbsp;5c and\u0026nbsp;Supplementary Fig.\u0026nbsp;31) from\u0026nbsp;five\u0026nbsp;soft pack batteries (~20\u0026thinsp;wt.% yield; Supplementary Fig. 30d). After exfoliation, the scaled-up production of 110.7 g of 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e NSs (Extended Data Fig. 4a) can be collected in solid state. Further, the MoS\u003csub\u003e2\u003c/sub\u003e NSs can be easily fabricated onto a flexible polyvinylidene difluoride (PVDF) substrate by vacuum filtration (Extended Data Fig. 4b-c) and cross-sectional SEM image (Extended Data Fig. 4d) reveals the typical lamellar and compact architecture of MoS\u003csub\u003e2\u003c/sub\u003e film.\u0026nbsp;Fig. 5d\u0026nbsp;shows comparisons of the\u0026nbsp;2H or 1T\u0026rsquo; phase\u0026nbsp;and scalability of\u0026nbsp;co-intercalation/solvent-free intercalation\u0026nbsp;and exfoliation for producing TMDs NSs\u0026nbsp;with other exfoliation methods, such as\u0026nbsp;Li-ion electrochemical exfoliation\u003csup\u003e34\u003c/sup\u003e, n-BuLi chemical exfoliation\u003csup\u003e23\u003c/sup\u003e, nap-Li chemical exfoliation\u003csup\u003e5\u003c/sup\u003e, solid lithiation for exfoliation\u003csup\u003e38\u003c/sup\u003e, \u0026nbsp;solution-processable exfoliation\u003csup\u003e18\u003c/sup\u003e, mild electrochemical exfoliation\u003csup\u003e39\u003c/sup\u003e, solvent lithium intercalation for exfoliation\u003csup\u003e17\u003c/sup\u003e and\u0026nbsp;solvent-assisted mechanical exfoliation\u003csup\u003e20\u003c/sup\u003e (details shown in\u0026nbsp;Supplementary Table 1). Our method enables the batch preparation\u0026nbsp;(hundred-gram range) of\u0026nbsp;1T\u0026rsquo;- and 2H-\u0026nbsp;TMDs with high phase purity\u0026nbsp;among all methods.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eHigh-phase-purity TMDs NSs synthesized via lithiation-exfoliation show promise for applications in catalysis, energy storage, and electronic devices due to their scalable production potential\u003csup\u003e43,44\u003c/sup\u003e. As demonstrated, 2H- and 1T\u0026rsquo;- MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e NSs were used as electrocatalysts for NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e reduction reaction (NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003eRR) (see detail in Methods and Supplementary Fig.\u0026nbsp;32-34). The 1T\u0026rsquo; phase NSs (MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e) possessed higher reduction currents and Faraday efficiencies for NH\u003csub\u003e3\u003c/sub\u003e production comparing the pure 2H phase and the 1T\u0026rsquo;/2H mixed phase NSs (Fig. 5e-f and Supplementary Fig. 35) at high overpotentials (after \u0026minus;0.65 V). Among them, 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e exhibits highest reduction current density up to ~2.0 A cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e with a Faraday efficiency of more than 92%, achieving a high NH\u003csub\u003e3\u003c/sub\u003e production rate of 143.4 mg h\u003csup\u003e\u0026minus;1\u003c/sup\u003e cm\u003csup\u003e\u0026minus;2\u0026nbsp;\u003c/sup\u003e(Fig. 5g), which is still stable for 100 h of electrolysis at an industrial-grade current density of 1.0 A cm\u003csup\u003e\u0026minus;2\u003c/sup\u003e (Extended Data Fig. 5a). Compared with previous works, it has obvious advantages in terms of reduction current and Faraday efficiency (Extended Data Fig. 5b and Supplementary Table 2).\u003c/p\u003e\n\u003cp\u003eDFT calculations were used to explore the catalytic performances of different phases for nitrate reduction.\u0026nbsp;We first compare the electronic structures of 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e, 1T\u0026rsquo;-MoS\u003csub\u003e2\u003c/sub\u003e,\u003csub\u003e\u0026nbsp;\u003c/sub\u003eand 1T\u0026rsquo;-MoSe\u003csub\u003e2\u003c/sub\u003e through the projected partial density of states (PDOS) (Supplementary Fig.\u0026nbsp;36). For the S-3p orbitals, a gradual upshifting is noted from WS\u003csub\u003e2\u003c/sub\u003e to MoS\u003csub\u003e2\u003c/sub\u003e. In MoSe\u003csub\u003e2\u003c/sub\u003e, the Se-4p orbitals become further closer to the Fermi level, inducing reduced overlapping between Mo-4d and Se-4p orbitals for electron transfer. Accordingly, the corresponding d-band and p-band centers of 1T\u0026rsquo; phases are summarized (Supplementary Fig.\u0026nbsp;37). Notably, the d-band and p-band centers display a converse trend from WS\u003csub\u003e2\u003c/sub\u003e to MoSe\u003csub\u003e2\u003c/sub\u003e, supporting the reduced electroactivity due to the weakened p-d coupling with the enlarged mismatch of orbitals. These results confirm the highest electroactivity of 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e for nitrate reduction.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe PDOS are further compared to demonstrate the phase influences on the MoS\u003csub\u003e2\u003c/sub\u003e and WS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(Supplementary Fig.\u0026nbsp;38). It is apparent that the 2H-WS\u003csub\u003e2\u003c/sub\u003e and 2H-MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eare semiconductors with evident band gaps for electron transfer while the 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e and 1T\u0026rsquo;-MoS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003eexhibit metallic-like properties with much higher electron transfer efficiency, which guarantees the higher electroactivity of 1T\u0026rsquo; phase for nitrate reduction. In the end, the reaction trends for nitrate reduction have been compared to 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e and 2H-WS\u003csub\u003e2\u0026nbsp;\u003c/sub\u003e(Supplementary Fig.\u0026nbsp;39). The 1T\u0026rsquo; phase displays a stronger reaction trend than the 2H phase, where the rate-determining step (RDS) is the reduction of *NO\u003csub\u003e2\u003c/sub\u003e to *NO. The RDS barrier of the 1T\u0026rsquo; phase is only 0.48 eV, which is only half that of the 2H phase (1.08 eV), supporting the improved nitrate reduction performance in 1T\u0026rsquo;-WS\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e\n\u003cp\u003eIn summary, we have developed a general phase-controlled intercalation-exfoliation method for the hundred-gram synthesis of high-phase-purity TMDs nanosheets,\u0026nbsp;offering a scalable alternative to traditional manufacturing methods. Enhanced NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003eRR performance of 1T\u0026rsquo; TMDs suggested their potential applications as a high-performance catalyst. The intercalation mechanism allowed for the selective exfoliation of 1T\u0026rsquo;- and 2H- MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e and the 1T\u0026rsquo;/2H heterophase monolayer or bi-layer by tuning electrochemical engineering. Our method provides straightforward access to pure 1T\u0026rsquo;, 2H, and heterophase NSs, facilitating the study of their unique properties. This advancement not only accelerates foundational research but also broadens their utility in fields including topological electronics, catalysis, energy storage, and flexible electronics.\u003c/p\u003e"},{"header":"Online content","content":"\u003cp\u003eAny methods, additional references, Nature Portfolio reporting summaries, source data, extended data, supplementary information, acknowledgements, peer review information; details of author contributions and competing interests; and statements of data and code availability are available at https://doi.org/xxx.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cstrong\u003eMaterials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eLithium hexafluorophosphate (LiPF\u003csub\u003e6\u003c/sub\u003e,\u0026nbsp;99.9%), Propylene carbonate (PC, 99.9%), Diethylene glycol dimethyl ether (DEGDME, 99.9%), Dimethyl sulfoxide (DMSO, 99.9%),\u0026nbsp;Li foils\u0026nbsp;(99.9%),\u0026nbsp;Copper foil (99.9%),\u0026nbsp;N-methyl-2-pyrrolidone (NMP, 99%), Polyvinylidene difluoride (PVDF, 99%), Molybdenum disulfide (MoS\u003csub\u003e2\u003c/sub\u003e, 99%), Tungsten disulfide (WS\u003csub\u003e2\u003c/sub\u003e, 99%), and Molybdenum diselenide (MoSe\u003csub\u003e2\u003c/sub\u003e, 99%),\u0026nbsp;Nafion 117-containing solution (5%), Ethanol (99%).\u0026nbsp;The\u0026nbsp;traditional\u0026nbsp;electrolyte\u0026nbsp;(1.0 M LiPF\u003csub\u003e6\u003c/sub\u003e in EC and DEC) was purchased from DodoChem Technology Co., Ltd.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eElectrolyte preparation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMolecular sieves were used to dry the solvents before electrolyte preparation. LiPF\u003csub\u003e6\u003c/sub\u003e was dissolved in the solvent within an Argon-filled glove box (with H\u003csub\u003e2\u003c/sub\u003eO\u0026nbsp;and\u0026nbsp;O\u003csub\u003e2\u003c/sub\u003e level\u0026lt; 0.1 ppm) to prepare co-intercalation and solvent-free-intercalation electrolytes. Detailed compositions of the electrolytes used in this work are as follows: (i) for traditional Li-ion intercalation electrolyte: 1.0 M LiPF\u003csub\u003e6\u003c/sub\u003e in EC:DEC (v/v: 50:50); (ii) for 1T\u0026rsquo;- MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e: 1.0 M LiPF\u003csub\u003e6\u003c/sub\u003e in PC; (iii) for 2H- MoS\u003csub\u003e2\u003c/sub\u003e: 1.0 M LiPF\u003csub\u003e6\u003c/sub\u003e in DEGDME; and (iv) for 2H- WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e: 1.0 M LiPF\u003csub\u003e6\u003c/sub\u003e in DMSO.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of 2H- and 1T\u0026rsquo;-TMDs NSs.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePhase-pure 2H- and 1T\u0026rsquo;-TMDs NSs were synthesized via a controlled electrochemical Li\u003csup\u003e+\u003c/sup\u003e intercalation-exfoliation process. This method was carried out within a coin cell setup. The cell assembly steps were performed in an Argon-filled glovebox, employing 600-\u0026micro;m-thick Li foils as the lithium source and 40 \u0026mu;L of electrolyte per cell. TMD electrodes (MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e, and MoSe\u003csub\u003e2\u003c/sub\u003e) were fabricated by mixing bulk TMD powder (80 wt.%), carbon black (10 wt.%), and PVDF (10 wt.%) in NMP, while graphite anodes consisted of carbon black, PVDF, and graphite (1:1:8 mass ratio) coated on Cu foil and dried at 80\u0026deg;C under vacuum for 12\u0026thinsp;h. The key differences in the synthesis of 2H-\u0026nbsp;and 1T\u0026rsquo;-TMDs\u0026nbsp;NSs are associated with the cut-off\u0026nbsp;voltage\u0026nbsp;and temperature\u0026nbsp;during the galvanostatic discharge.\u0026nbsp;For the production of 2H-MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e,\u0026nbsp;these critical parameters were established 1.1 V, 0.9 V and 0.9 V, respectively, and all are at room temperature. Whereas for\u0026nbsp;1T\u0026rsquo;-\u0026nbsp;MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e, the temperatures were set at 110\u0026nbsp;\u0026deg;C, 150\u0026nbsp;\u0026deg;C\u0026nbsp;and 110\u0026nbsp;\u0026deg;C, and all were discharged to 0.7 V (discharge curves are shown in Supplementary Fig. 12, 14). All battery tested with a current of 0.1 C (167.4 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e for MoS\u003csub\u003e2\u003c/sub\u003e, 108.1 mAh g\u003csup\u003e\u0026minus;1\u003c/sup\u003e for WS\u003csub\u003e2\u003c/sub\u003e and 105.6 mAh g\u003csup\u003e\u0026minus;1\u0026nbsp;\u003c/sup\u003efor MoSe\u003csub\u003e2\u003c/sub\u003e). Additionally, 2H-TMDs NSs were prepared by sonication in ethanol: DI water =1:1, whereas 1T\u0026rsquo; -TMDs NSs were fabricated through sonication in pre-oxygenated DI water. After sonication, the 2H and 1T\u0026rsquo; suspensions were subjected to centrifugation and repeated washing before final redispersion in DI water for characterization and subsequent use.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterial Characterizations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eADF-STEM (JEOL ARM200F spherical aberration-corrected transmission electron microscope operated at 200kV). TEM (FEI talosf200s). XPS (Thermo Scientific K-Alpha Nexsa), STEM (JEOL-ARM300). Raman spectroscopy (WITec alpha 300 confocal Raman microscope, 532 nm). XAS (Beijing Synchrotron Radiation Facility, beamline 4B9A/1W2A, transmission mode). AFM (Dimension 3100, Veeco, CA). SEM (JSM-7600). UV-vis spectrophotometer (UH 4150 UV, Hitachi). ICP-MS (PE Nexion 2000). XRD (Bruker D8 diffractometer, Cu K\u0026alpha; radiation source).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNO\u003csub\u003e3\u003c/sub\u003e\u003c/strong\u003e\u003cstrong\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;reduction reaction\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;measurement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe electrochemical NO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026ndash;\u003c/sup\u003e reduction reactions were performed in a custom H-type cell, with a CHI660E workstation recording the electrochemical responses. The catholyte consisted of 1.0 M KNO\u003csub\u003e3\u003c/sub\u003e and 3 M KOH, while the anolyte contained 3 M KOH alone. In a typical three-electrode system, a Pt foil and a Hg/HgO electrode were used as the counter and reference electrodes, respectively. A Nafion 117 proton exchange membrane separated the anolyte and catholyte chambers. All potentials measured against Hg/HgO were converted to the RHE scale using the equation: E (vs. RHE) = E (vs. Hg/HgO) + 0.241 V + 0.0098\u0026times;pH, with 85% \u003cem\u003eiR\u003c/em\u003e compensation applied unless stated. Electrochemical impedance spectroscopy (EIS) was conducted over a frequency range of 0.1 Hz to 100 kHz. Synthesized 1T\u0026rsquo;- MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and MoSe\u003csub\u003e2\u003c/sub\u003e, 2H- MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e and 1T\u0026rsquo;/2H mixed MoS\u003csub\u003e2\u003c/sub\u003e were directly used as the working electrode. For the working electrode preparation, TMDs inks were dispersed in alcohol with Nafion 117, sonicated for 40 min, and 160 \u0026micro;L of the catalyst ink was drop-casted onto a 0.5\u0026times;\u0026thinsp;0.5\u0026thinsp;cm\u003csup\u003e2\u003c/sup\u003e carbon paper, achieving a loading of 0.3\u0026thinsp;mg\u0026thinsp;cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e. Linear sweep voltammetry tests were recorded at 10\u0026thinsp;mV\u0026thinsp;s\u003csup\u003e\u0026ndash;1\u003c/sup\u003e, while chronoamperometric tests were conducted at different potentials for 1.0 hours with a rotation rate of 300 rpm. Long-term stability was\u0026nbsp;evaluated via chronopotentiometry tests at 1.0\u0026thinsp;A\u0026thinsp;cm\u003csup\u003e\u0026ndash;2\u003c/sup\u003e. All the measurements were conducted at room temperature under ambient pressure.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe concentration of NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e\u0026ndash;N was quantified using the Nessler\u0026rsquo;s reagent method. A fixed volume of catholyte was extracted and diluted to 10 mL for analysis within the instrument\u0026rsquo;s detection range. Potassium sodium tartrate solution (0.2 mL, 500 g L\u003csup\u003e\u0026ndash;1\u003c/sup\u003e) and Nessler\u0026rsquo;s reagent (0.2 mL) were sequentially added, followed by thorough mixing. After a 20-minute equilibration period, absorbance was measured at 420 nm. A calibration curve was constructed using standard NH\u003csub\u003e4\u003c/sub\u003eCl solutions with varying NH\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e+\u003c/sup\u003e\u0026ndash;N concentrations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComputational details\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn this study, we employed DFT calculations using the CASTEP package to investigate binding energies, desolvation energies, electronic structures, and reaction energy changes\u003csup\u003e45\u003c/sup\u003e. For all the calculations, we have chosen the generalized gradient approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) functionals to accurately describe the exchange-correlation energy\u003csup\u003e46-48\u003c/sup\u003e. Based on the ultrafine quality, the plane-wave basis cut-off energy has been set to 380 eV, and the ultrasoft pseudopotentials are applied for the calculation. Meanwhile, to balance precision and efficiency, the Broyden-Fletcher-Goldfarb-Shannon (BFGS) algorithm and coarse k-point sampling were implemented\u003csup\u003e49\u003c/sup\u003e. A 20 \u0026Aring; vacuum space along the z-axis ensured sufficient room for geometry relaxation. Convergence criteria included total energy differences below 5\u0026times;10⁻\u003csup\u003e5\u003c/sup\u003e eV/atom, Hellmann-Feynman forces under 0.001 eV/\u0026Aring;, and inter-ionic displacements limited to 0.005 \u0026Aring;. The MD simulations have been performed through the Forcite packages, where the electrolytes are constructed with Li\u003csup\u003e+\u003c/sup\u003e: electrolyte = 1:4. For each electrolyte model, there are four layers of MoS\u003csub\u003e2\u003c/sub\u003e. Equilibrated models underwent NVT-ensemble simulations at 298 K, controlled by the Universal forcefield and Nos\u0026eacute; thermostat. A 1.0 ns simulation with 1.0 fs time steps (totaling 1\u0026times;10\u003csup\u003e6\u003c/sup\u003e steps) ensured dynamic stability.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e: All data supporting the findings of this study are available in the paper and its Supplementary Information. Other raw data is available from the corresponding authors on request. Source data are provided with this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e: Z.Y. Zeng thanks the Young Collaborative Research Grant [Project No. C1003-23Y] and General Research Fund (GRF) [Project No. CityU11308923 and CityU 11309824] support from the Research Grants Council of the Hong Kong Special Administrative Region, China, the Applied Research Grant of City University of Hong Kong (project no of 9667247) and Chow Sang Sang Group Research Fund of City University of Hong Kong (project no of 9229123). Z.Y. Zeng also thanks the funding supported by the Seed Collaborative Research Fund Scheme of State Key Laboratory of Marine Pollution which receives regular research funding from the Innovation and Technology Commission (ITC) of the Hong Kong SAR Government. However, any opinions, findings, conclusions or recommendations expressed in this publication do not reflect the views of the Hong Kong SAR Government or the ITC.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e:\u0026nbsp;Z. Zeng conceived and guided the project.\u0026nbsp;H.\u0026nbsp;Hu\u0026nbsp;designed and performed the synthesis and characterizations of all the materials.\u0026nbsp;H. Hu\u0026nbsp;and\u0026nbsp;Q. Zhang\u0026nbsp;performed the device fabrication and performance test. D.\u0026nbsp;Voiry, Y.\u0026nbsp;Chai, R.\u0026nbsp;Ye, B. Liu and\u0026nbsp;X.\u0026nbsp;Zhang helped to analyze the results. M.\u0026nbsp;Sun and\u0026nbsp;B.\u0026nbsp;Huang\u0026nbsp;conducted the DFT calculations\u0026nbsp;and MD simulations.\u0026nbsp;Z. Zhang\u0026nbsp;performed the HAADF-STEM test of the samples.\u0026nbsp;H. Hu,\u0026nbsp;M. Sun,\u0026nbsp;B. Liu, K.Loh, J. Li,\u0026nbsp;and Z. Zeng drafted the paper. All authors checked the paper and agreed with its content.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e: The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSupplementary information\u0026nbsp;\u003c/strong\u003eThe online version contains supplementary material available at https://doi.org/xxx.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrespondence and requests for materials\u0026nbsp;\u003c/strong\u003eshould be addressed to Zhiyuan Zeng.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePeer review information\u003c/strong\u003e \u003cem\u003eNature\u0026nbsp;\u003c/em\u003ethanks xxx and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReprints and permissions information\u003c/strong\u003e is available at http://www.nature.com/reprints.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eVoiry, D., Mohite, A. \u0026amp; Chhowalla, M. 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However, exfoliation of high-phase-purity atomic-layer transition-metal dichalcogenide (TMD) nanosheets remains a challenge. Conventional methods based on alkali metal-ion intercalation (Li\u003csup\u003e+\u003c/sup\u003e, Na\u003csup\u003e+\u003c/sup\u003e, K\u003csup\u003e+\u003c/sup\u003e) yield MoS\u003csub\u003e2\u003c/sub\u003e or WS\u003csub\u003e2\u003c/sub\u003e flakes with uncontrolled phase mixing (2H/1T hybridization), severely limiting their functional reproducibility. Here, we demonstrate that phase-selective exfoliation for fabricating phase-pure 2H and 1T' TMD atomically thin nanosheets is both scalable and reliable. This process involves the electrochemical co-intercalation of Li-solvent (e.g., Li\u003csup\u003e+\u003c/sup\u003e-diethylene glycol dimethyl ether) and solvent-free Li-ion intercalation (e.g., propylene carbonate-based electrolyte) into 2H phase TMD crystal powders, followed by mild sonication and exfoliation. Quantitative modulation of the intercalation depth allows deterministic phase targeting, achieving monolayer yields exceeding 90% for 1T'-MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e, and MoSe\u003csub\u003e2\u003c/sub\u003e, and bilayer/trilayer 2H-MoS\u003csub\u003e2\u003c/sub\u003e, WS\u003csub\u003e2\u003c/sub\u003e, and MoSe\u003csub\u003e2\u003c/sub\u003e with yields above 75%. Phase hybridization is further engineered at atomic precision, generating heterophase MoS\u003csub\u003e2\u003c/sub\u003e nanosheets with 1T' ratios tunable from 13% to 92% via electrosynthesis parameters. Further, our approach enables the mass production of high-phase-purity MoS\u003csub\u003e2\u003c/sub\u003e nanosheets on a hundred-gram scale via controlled charging of a LiFePO\u003csub\u003e4\u003c/sub\u003e||MoS\u003csub\u003e2\u003c/sub\u003e pouch-cell configuration. This universal and selective synthesis of ultrathin TMD nanosheets presents opportunities to accelerate the exploration of electronic and photonic properties.","manuscriptTitle":"Electrochemical engineering for phase-controlled exfoliation of transition metal dichalcogenides","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-22 05:12:28","doi":"10.21203/rs.3.rs-6516593/v1","editorialEvents":[],"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":"6951e044-cf00-4ec7-b3e2-95b3bf83da69","owner":[],"postedDate":"May 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":48810209,"name":"Physical sciences/Materials science/Nanoscale materials/Two-dimensional materials"},{"id":48810210,"name":"Physical sciences/Materials science/Nanoscale materials/Electronic properties and materials"}],"tags":[],"updatedAt":"2026-01-28T10:46:04+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-22 05:12:28","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6516593","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6516593","identity":"rs-6516593","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}