Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction

Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction | 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 Research Article Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction Hongna Cheng, Chaoyong Wang, Zihan Wang, Weikang Peng, Jiayi Hou, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7803669/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract The climate crisis caused by excessive carbon dioxide (CO 2 ) emissions urgently call for efficient electrocatalytic reduction technology to convert CO 2 into high value-added products. In this study, nickel polyphthalocyanine (NiPPc) electrocatalysts with different copper (Cu) doping amounts (10-90wt%) were prepared by solvothermal method, Combining X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and other characterization and electrochemical testing, it is found that: Doping with 10 wt% Cu significantly enhanced catalytic activity, achieving a current density of 325 mA·cm − 2 at -0.6 V (vs. RHE)—2.8 times that of the undoped sample;50 wt% Cu doping optimized the Cu–N 4 active sites, yielding a carbon monoxide (CO) Faraday efficiency of up to 95% at -1.0 V; 30 wt% Cu-doped catalyst can generate CO:H 2 = 1:1 syngas, A controllable catalyst design strategy is provided for CO 2 electrocatalytic reduction. Cu ion doping NiPPc Electrocatalyst CO2 reduction Electrochemical properties Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction The global climate crisis caused by CO 2 emissions [ 1 – 4 ] urgently demands efficient carbon conversion technologies. The current mainstream CO 2 reduction strategies include biological fixation [ 5 – 7 ] , chemical adsorption [ 8 , 9 ] , thermal catalysis [ 10 , 11 ] and geological sequestration [ 12 , 13 ] , etc: Biological fixation relies on photosynthesis by plants or microbes to assimilate CO 2 ; however, it suffers from low sequestration efficiency, long cycles, and environmental limitations; Although chemisorption techniques (such as amine washing [ 14 , 15 ] , metal-organic framework materials [ 16 , 17 ] ) can achieve efficient capture, However, the energy consumption of adsorbent regeneration is high and the cycle stability is poor.Although thermocatalytic CO 2 reduction offers a wide product spectrum, simple equipment, and low cost—making it attractive for large-scale deployment [ 18 ] —its long-term feasibility remains contentious. Geological storage of CO 2 needs to be compressed and injected into deep geological structures, but there is a risk of leakage and long-term monitoring problems.In contrast, electrocatalytic CO 2 reduction (eCO 2 RR) technology is considered a key path to achieving carbon neutrality by driving the conversion of CO 2 into high value-added chemicals (e.g., CO [ 19 , 20 ] , syngas [ 21 – 23 ] , hydrocarbons [ 24 – 26 ] , hydrocarbon derivatives [ 27 , 28 ] , etc.), which have the advantages of carbon recycling and energy storage [ 29 , 30 ] .However, eCO 2 RR faces the dual challenge of the high stability of CO 2 molecules and competition from the side reaction of hydrogen evolution (HER),Phthalocyanine compounds have advantages such as easy synthesis, low cost, and adjustable structure, making them ideal catalytic materials for eCO 2 RR.Among the polyphthalocyanine materials with metal centers such as iron [ 31 , 32 ] , cobalt [ 33 , 34 ] , nickel [ 35 , 36 ] , and copper [ 37 , 38 ] , NiPPc stands out with its unique M-N 4 coordination structure and adjustable electronic properties, but it still has problems such as overly strong intermediate adsorption and slow reaction kinetics [ 39 , 40 ] . This leads to insufficient low-potential activity and intensifies the hydrogen evolution side reaction.To overcome this technical bottleneck, Cu, with its precise *COOH intermediate adsorption regulation characteristics, can dynamically balance the CO desorption kinetics and the C-C coupling reaction process [ 41 ] , demonstrating a synergistic effect in achieving the directional synthesis of multi-carbon products and the regulation of syngas components [ 42 , 43 ] .Based on the above findings, this study innovatively proposes to directionally regulate the electronic structure characteristics of NiPPc materials through copper ion doping strategies and reconstruct the coordination configuration of their surface catalytic sites. The experiment precisely constructed the gradient Cu-doped NiPPc: Cu catalyst by solvothermal method, and systematically studied the influence of doping amount on the CO 2 reduction performance.Cu-ion doping engineering effectively modulated both the geometric structure and electronic properties of the active sites, leading to enhanced catalytic activity and tunable product selectivity. This provides a solid theoretical basis and practical solutions for designing efficient CO 2 RR catalysts. Experimental Materials The Nickel acetate tetrahydrate (Ni(CH 3 COO) 2 ·4H 2 O), copper acetate monohydrate (Cu(CH 3 COO) 2 ·H 2 O), 1,2,4,5-tetracyanobenzene (C 10 H 2 N 4 ) and Nafion were supplied by Shanghai Maikelin Bioengineering Technology Co., Ltd. Ethanol (CH 3 CH 2 OH), sulfuric acid (H 2 SO 4 ) and hydrogen peroxide (H 2 O 2 ) were obtained from Tianjin Yongda Chemical Reagent Co., Ltd. Potassium bicarbonate (KHCO 3 ) was provided by Shanghai Aladdin Biochemical Technology Co., Ltd. Preparation of electrocatalysts Using the solvothermal method, the specific experimental process is as follows: Ni(CH 3 COO) 2 ·4H 2 O, C 10 H 2 N 4 , and Cu(CH 3 COO) 2 ·H 2 O were weighed in the desired ratios and sequentially added to 35 mL of ethanol.The mixture was stirred at 500 rpm for 30 min, sonicated for 1 h, then heated in an autoclave at 180°C for 24 h. After naturally cooling to room temperature, centrifuge wash with anhydrous ethanol (8000 rpm, 5 min, repeated 3 times), the obtained precipitate is dried in a vacuum oven at 80°C for 12 hours, and after grinding, NiPPc: Cu powder is obtained. Installation and testing of electrochemical equipment Working-electrode fabrication: Carbon paper (1 cm × 1.5 cm) was calcined at 200°C for 3 h under Ar. A catalyst ink (4 mg catalyst, 960 µL EtOH, 40 µL Nafion) was sonicated for 30 min; 100 µL of the ink was drop-cast onto 1 cm² of the carbon paper in two aliquots and dried under UV. Membrane pretreatment: Nafion 115 was boiled in deionized water (30 min), treated with 3% H 2 O 2 at 80°C (1 h), rinsed again in boiling water (30 min), immersed in 1 M H 2 SO 4 (30 min), and finally washed in boiling water (30 min) before storage in deionized water. Electrolyte: 0.5 M KHCO 3 (10.012 g in 200 mL H 2 O). Electrolytic cell assembly:The pretreated membrane was clamped between the two chambers, each filled with 30 mL electrolyte. CO 2 was supplied to the catholyte at 10 mL min − 1 for 30 min. An Ag/AgCl electrode and Pt foil served as reference and counter electrodes,The test potential was converted using the formula E(vs.RHE) = E(vs.Ag/AgCl) + 0.197 + 0.0592 × pH (1).Using linear sweep voltammetry (LSV) to analyze the initial potential and current density of the sample to evaluate the performance of the catalyst.Electrochemical impedance spectroscopy (EIS) obtains the reaction kinetics of the materials.The electrochemical active surface area (ECSA) was calculated using the formula ECSA = Cdl/Cs (2), which reflects the accommodation of catalytic sites.By combining electrochemical testing with gas chromatography analysis, the Faradaic efficiency is calculated using the I-t data through formula (3).By calculating the CO partial current density through equation \(\:{\text{j}}_{\text{C}\text{O}}={\text{j}}_{\text{总}}\times\:{\text{x}}_{\text{C}\text{O}}\) (4) and analyzing the CO/H 2 ratio, the CO 2 reduction efficiency, product selectivity and syngas tunability. Physical characterization This study systematically analyzes the characteristics of samples through multi-dimensional representation technology: Characterization and analysis of the sample's phase and crystal structure using X-ray diffraction (XRD, D/MAX2500PC); Using a Fourier Transform Infrared Spectrometer (FT-IR, VERTEX70) to accurately analyze molecular structure and identification; At the same time, the chemical bond vibrations and chemical bond information were obtained using the micro-Raman spectrometer (DXR);Observe the morphological characteristics of the catalyst nanoscale structure through transmission electron microscopy (TEM, HT-7800) and conduct elemental mapping analysis;Further use of X-ray photoelectron spectroscopy (XPS, Thermo Kalpha) to deeply analyze the chemical state and elemental valence state of the material surface. Results and Discussion The effect of Cu ion doping amount on the structure of NiPPc: Cu Using nickel content as a benchmark, copper ions are introduced into the system in mass proportions, with the amounts set at 10%, 30%, 50%, 70%, and 90% of the nickel content.The series of materials prepared are sequentially named as 10 wt% NiPPc: Cu, 30 wt% NiPPc: Cu, 50 wt% NiPPc: Cu, 70 wt% NiPPc: Cu, and 90 wt% NiPPc: Cu. XRD patterns (Fig. 1 ) show that the polyphthalocyanine peak at ~ 27° weakens and broadens upon initial Cu incorporation, indicating a loss of crystallinity. Within the NiPPc:Cu series, however, the ~ 27° reflection gradually regains intensity as the Cu level increases, pointing to a partial restoration of structural order. FT-IR spectra (Fig. 2 a) show that the phthalocyanine-ring vibrations are more intense for 30 wt % NiPPc:Cu than for pristine NiPPc; the intensity remains above the NiPPc level up to 90 wt % Cu, indicating that ≥ 30 wt % Cu promotes phthalocyanine formation, whereas 10 wt % Cu suppresses it. The terminal C ≡ N stretch at 2 231 cm⁻¹ also gains intensity at 30 wt % Cu, confirming enhanced C–N bond formation. Raman spectra (Fig. 2 b) display a weak but consistent metal-phthalocyanine band at ~ 1 560 cm⁻¹ across all Cu loadings, corroborating the FT-IR conclusions. TEM (Fig. 3 a,b) reveals uniform ~ 500 nm spheres whose morphology is preserved after Cu introduction. Elemental maps (Fig. 3 c–f) show homogeneous distributions of Ni, Cu, N and C, evidencing successful NiPPc:Cu formation. The EDS spectrum (Fig. 4 ) corroborates the uniform incorporation of Cu within the NiPPc matrix. The survey XPS scan (Fig. 5 a) confirms the presence of Ni, Cu, N and C, verifying NiPPc:Cu formation. The Cu 2p region (Fig. 5 b) exhibits broad, poorly fitted peaks at 934.98 eV (Cu 2p 3/2 ) and 955.27 eV (Cu 2p 1/2 ), indicating that Cu is predominantly Cu(II) with a minor Cu(I) contribution, but is not fully incorporated into the phthalocyanine lattice. Ni 2p and C 1s spectra (Fig. 5 b,c) show negligible shifts, whereas the N 1s signal (Fig. 5 d) reveals a marked weakening of the Ni–N bond, evidencing electronic perturbation of the macrocycle upon Cu introduction. The effect of Cu ion doping amount on the CO 2 reduction performance of NiPPc: Cu Activity tests (Fig. 6 a) show that 10 wt % Cu improves low-overpotential stability through structural uniformity, whereas 50 wt % Cu tunes *COOH adsorption via Cu–N₄ sites; together they optimise overall performance. Between − 0.6 and − 0.9 V vs. RHE the doped catalysts deliver lower current than pristine NiPPc, but beyond ~ 1 V overpotential all Cu-containing samples outperform the parent material. In the 10–15 mA cm − 2 window the potentials required decrease in the order 30 > 10 > 90 > 50 > 70 wt % NiPPc: Cu, while at higher densities the polarisation curves converge. EIS (Fig. 6 b) reveals larger charge-transfer resistance for the doped electrodes, indicating compromised kinetics. As seen in Fig. 7 , the low scanning speed has little effect on the CV of NiPPc:Cu, as derived from Fig. 7 (f) based on Figs. 7 (a-e). Figure 7 (f) shows that the double layer capacitance of 10 wt% NiPPc: Cu, 50 wt% NiPPc: Cu, and 70 wt% NiPPc: Cu is higher than that of NiPPc (0.809429 mF·cm − 2 ), which are 2.76 mF·cm − 2 , 3.25 mF·cm − 2 , and 1.02 mF·cm − 2 , respectively;But 30 wt% NiPPc: Cu (0.163143 mF·cm − 2 ) and 90 wt% NiPPc: Cu (0.270214 mF·cm − 2 ) are lower than NiPPc. To investigate the effect of doping Cu on the stability of NiPPc, I-t tests were conducted. As can be seen from Fig. 8 , at a potential of − 0.8 V vs. RHE shows that 10 wt % NiPPc:Cu sustains 5 mA cm − 2 , whereas NiPPc and all other Cu-doped variants deliver only ~ 2.5 mA cm − 2 , evidencing enhanced low-potential activity with light Cu loading. Over 3 600 s the current density of 10 wt % NiPPc: Cu remains virtually unchanged, confirming superior stability. When the doping amount of Cu is 10% and 90%, the trend of the catalyst's selectivity to CO is consistent, both first increasing and then decreasing.At−0.8 V (vs.RHE), the selectivity for CO of 90 wt% NiPPc: Cu was lower than that of 10 wt% NiPPc: Cu.However, in the range of−0.9 to−1.1 V (vs. RHE), the 90 wt% NiPPc: Cu has a higher selectivity for CO.For 30 wt% NiPPc: Cu, at potentials of−0.8 V and−0.9 V (vs.RHE), the Faradaic efficiency for CO is about 50%, with a CO to H 2 ratio of 1:1 (Fig. 9 (d)).When the amount of Cu doping increases to 50 wt% and 70 wt%, the catalyst shows a significant enhancement in selectivity for CO in the high potential range (−0.8 to−1.1 V (vs.RHE) ).The CO faradaic efficiency of 50 wt% NiPPc: Cu can reach over 65%, and can be as high as about 95% at−1.0 V (vs. RHE), achieving a jump in CO selectivity at high potentials (Fig. 9 (a) ).The performance is better than the recently reported M-N 4 type catalyst [ 44 ] ;The CO faradaic efficiency of 70 wt% NiPPc: Cu can be stably maintained at 80% at−0.8 to−1.0 V (vs. RHE). Overall, for the single product CO, 50 wt% NiPPc: Cu exhibits excellent CO 2 reduction performance.The CO Faradaic efficiency of 30 wt% NiPPc: Cu is about 50%, at which point the ratio of CO to H 2 was 1:1, allowing for precise control of the composition ratio of synthesis gas.At a lower potential (−0.8V (vs.RHE) ), 10 wt% NiPPc: Cu exhibits a CO partial current density of approximately 5 mA·cm − 2 (as shown in Fig. 9 (a) ),At the same time, the ratio of CO to H 2 is approximately 10, which can achieve a high level of CO 2 reduction performance. Therefore, 10 wt% NiPPc: Cu is the optimal catalyst choice in this case. Conclusion This study successfully constructed a copper ion gradient-doped nickel-based phthalocyanine complex (NiPPc: Cu) electrocatalyst through a heterogeneous atom doping strategy using a solvent thermal method.Through systematic and in-depth research, the effect of different copper ion doping levels on the structure and performance of the catalyst has been comprehensively explored.Systematic research indicates that high amounts of Cu contribute to the formation of phthalocyanine structures.In terms of performance, different doping amounts have varying effects on the catalyst activity, stability, and product selectivity.Low doping concentration improves stability, while high doping concentration regulates the adsorption pathways of intermediates.In terms of product selectivity, a 30 wt% can adjust the ratio of CO to H 2 to 1:1, while 50 wt% and 70 wt% enhance CO selectivity at high potentials.For a single CO product, 50 wt% NiPPc: Cu performs better.Synthesis gas selects 30 wt% NiPPc: Cu;Under low potential, the best CO 2 reduction performance was with 10 wt% NiPPc: Cu.This work delivers both theoretical insights and practical protocols for designing high-performance CO 2 RR catalysts, representing a significant advance toward the industrialization of electrocatalytic carbon-recycling technologies. Abbreviations Abbreviations full name CO carbon monoxide CO 2 carbon dioxide Cu(CH 3 COO) 2 ·H 2 O) copper(II) acetate monohydrate EtOH/CH 3 CH 2 OH ethanol H 2 hydrogen H 2 O 2 hydrogen peroxide H 2 SO 4 sulfuric acid KHCO 3 potassium bicarbonate Ni(CH 3 COO) 2 ·4H 2 O nickel(II) acetate tetrahydrate NiPPc nickel polyphthalocyanine NiPPc: Cu Cu-doped nickel polyphthalocyanine Nation perfluorosulfonic acid ionomer C 10 H 2 N 4 1,2,4,5-tetracyanobenzene *COOH carboxyl intermediate CO/H 2 syngas M–N 4 metal–nitrogen 4 coordination Declarations Ethics and Consent to Participate Not applicable. This work does not involve human participants, human data, human tissue, or animals. Consent for Publication All authors hereby solemnly declare that they have thoroughly reviewed and hereby affirmatively consent to submit this manuscript entitled "Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction" for publication in Catalysis Letters. Additionally, they commit to fully complying with all procedures stipulated by the journal's publication protocol and strictly adhering to regulations governing copyright transfer. Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Author Contribution H.N.C. and C.Y.W. conceived the project, designed the experiments and supervised the study,wrote the main manuscript. Z.H.W, W.K.P. and J.Y.H. systematically integrated the research background, methodology and findings, and finalized the core discussion.S.T.T. and Z.X.S. prepared all figures and tables, transforming experimental data into clear visual representations with professional graphing and statistical tools.Y.L. performed the electrocatalytic tests, materials characterization and data collection, ensuring reproducibility and reliability.All authors critically reviewed the draft, provided feedback on academic rigor and content accuracy, and approved the final version of the paper. Funding The authors gratefully acknowledge the support of the National Natural Science Foundation of China (Grant No. 5187209) and the Tangshan Basic Research Fund Project (No. 23130210E) Availability of data and materials Experimental data and materials used in this study are available upon reasonable request from the corresponding author. 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1","display":"","copyAsset":false,"role":"figure","size":32125,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of NiPPc: Cu with different Cu ion doping amounts\u003c/p\u003e\n\u003cp\u003eLegend: XRD patterns of NiPPc and NiPPc:Cu catalysts with varying Cu doping levels (10–90 wt%). The peak at ~27° corresponds to the phthalocyanine framework structure. Cu incorporation leads to peak broadening and reduced crystallinity, with partial structural recovery observed at higher Cu contents.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/80cb0058c86ebba4c2773c47.png"},{"id":94452480,"identity":"f8625f97-2ed5-4de0-ba74-c81d03f355a4","added_by":"auto","created_at":"2025-10-27 14:41:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":71523,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR diagram (a) and Raman diagram (b) of NiPPc: Cu with different Cu ion doping amount\u003c/p\u003e\n\u003cp\u003eLegend: (a) FT-IR and (b) Raman spectra of NiPPc and NiPPc:Cu samples. FT-IR shows enhanced phthalocyanine ring formation at ≥30 wt% Cu doping, evidenced by increased peak intensities. The Raman peak at ~1560 cm⁻¹ confirms the formation of metal–phthalocyanine structures.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/49531221490831298a1a6e16.png"},{"id":94452145,"identity":"b196cc9a-2555-443c-be69-44d47eab6d32","added_by":"auto","created_at":"2025-10-27 14:40:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":285353,"visible":true,"origin":"","legend":"\u003cp\u003eTEM diagram of NIPPC:Cu (a, b) and scanning diagram of elements (c)Ni, (d)Cu, (e)N and(f) C\u003c/p\u003e\n\u003cp\u003eLegend: (a, b) TEM images and (c–f) elemental mapping of 50 wt% NiPPc:Cu. The catalyst exhibits uniform spherical morphology (~500 nm) with homogeneous distribution of Ni, Cu, N, and C elements, confirming successful Cu incorporation into the NiPPc matrix.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/91169d11434dbba0d3bd61b6.png"},{"id":94452123,"identity":"23c73909-3639-49cb-9b2c-6071afab56b9","added_by":"auto","created_at":"2025-10-27 14:40:47","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":15399,"visible":true,"origin":"","legend":"\u003cp\u003eEDS diagram of NiPPC: Cu\u003c/p\u003e\n\u003cp\u003eLegend: EDS spectrum of 50 wt% NiPPc:Cu, confirming the presence and uniform distribution of Ni, Cu, N, and C elements in the catalyst.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/ca7c25df489ffc7aa567785c.png"},{"id":94451807,"identity":"deed07ae-60e1-47c9-a7d3-64f02ba942df","added_by":"auto","created_at":"2025-10-27 14:40:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":72222,"visible":true,"origin":"","legend":"\u003cp\u003eXPS diagram of NiPPC: Cu (a)-full spectrum diagram of NiPPC: Cu; And the fine spectra of elements (b) Ni, (c) Cu, (d) N and (e) C\u003c/p\u003e\n\u003cp\u003eLegend: (a) XPS survey spectrum of 50 wt% NiPPc:Cu showing the presence of Ni, Cu, N, and C. (b) Cu 2p spectrum indicates Cu(II) as the dominant oxidation state. (c, d) Ni 2p and N 1s spectra reveal weakened Ni–N bonding upon Cu doping, suggesting electronic structure modulation.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/b6ec07e19318577d0d26f3d3.png"},{"id":94451132,"identity":"2325e367-437b-4ac1-941b-cbede16409d4","added_by":"auto","created_at":"2025-10-27 14:39:52","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":71416,"visible":true,"origin":"","legend":"\u003cp\u003eLSV diagram and EIS diagram of NiPPc: Cu with different Cu doping amount\u003c/p\u003e\n\u003cp\u003eLegend: (a) LSV curves of NiPPc and NiPPc:Cu catalysts in CO\u003csub\u003e2\u003c/sub\u003e-saturated 0.5 M KHCO\u003csub\u003e3\u003c/sub\u003e. (b) EIS Nyquist plots showing increased charge transfer resistance upon Cu doping, indicating altered reaction kinetics.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/5b5ffe72e8013e5ec78a7bbe.png"},{"id":94452304,"identity":"60588b9b-286b-44f0-88be-0689f2a6ffca","added_by":"auto","created_at":"2025-10-27 14:40:58","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":112026,"visible":true,"origin":"","legend":"\u003cp\u003eCV and C\u003csub\u003edl\u003c/sub\u003e plots of NiPPc: Cu with different cu ion doping amounts (a) 10 wt%, (b) 30 wt%, (c) 50 wt%, (d) 70 wt%, and (e) 90 wt%.\u003c/p\u003e\n\u003cp\u003eLegend: (a–e) CV curves at various scan rates and (f) calculated electrochemical double-layer capacitance (C\u003csub\u003edl\u003c/sub\u003e) for NiPPc and NiPPc:Cu catalysts. 10 wt%, 50 wt%, and 70 wt% Cu-doped samples exhibit higher C\u003csub\u003edl\u003c/sub\u003e values, suggesting increased electrochemically active surface areas.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/e5c6a859194480faa7888684.png"},{"id":94451957,"identity":"a1f46dab-e3cb-4c27-bc3c-cce99fd2ae2a","added_by":"auto","created_at":"2025-10-27 14:40:34","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":103987,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e(\u003c/strong\u003ea) I-t diagram of NiPPc: Cu with different Cu ions (b)10 wt%, (c)-30 wt%, (d)50 wt%, (e)70 wt% and (f)90 wt%\u003c/p\u003e\n\u003cp\u003eLegend: I–t curves recorded at −0.8 V vs. RHE over 3600 s. 10 wt% NiPPc:Cu maintains a stable current density of ~5 mA·cm\u003csup\u003e-2\u003c/sup\u003e, demonstrating superior stability compared to other compositions.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/5db1b6e495897f967112b76a.png"},{"id":94452337,"identity":"2ed5bcbc-bf25-4c95-ac33-84e981ab921d","added_by":"auto","created_at":"2025-10-27 14:41:00","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":75746,"visible":true,"origin":"","legend":"\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e reduction performance diagrams of NiPPc: Cu with different Cu ion doping amount (a)FECO diagram, (b)FEH\u003csub\u003e2\u003c/sub\u003e diagram, (c)jCO diagram and (d)CO/H\u003csub\u003e2\u003c/sub\u003e diagram\u003c/p\u003e\n\u003cp\u003eLegend:(a) CO and H\u003csub\u003e2\u003c/sub\u003e Faradaic efficiencies of NiPPc:Cu catalysts at various potentials. (b–e) CO/H\u003csub\u003e2\u003c/sub\u003e ratio tuning achieved via Cu doping: 30 wt% NiPPc:Cu yields a 1:1 syngas ratio, while 50 wt% achieves ~95% CO selectivity at −1.0 V. (f) CO partial current density showing optimal CO\u003csub\u003e2\u003c/sub\u003eRR performance for 10 wt% NiPPc:Cu at low overpotential.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/a5fb79a99bfb0300b61728ca.png"},{"id":94491354,"identity":"ff418ff7-643c-41cd-87ef-64c25ecc8514","added_by":"auto","created_at":"2025-10-27 17:24:33","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1346547,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7803669/v1/4e7f6c8c-a01f-488e-956e-c85c9a3fb687.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe global climate crisis caused by CO\u003csub\u003e2\u003c/sub\u003e emissions \u003csup\u003e[\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e urgently demands efficient carbon conversion technologies. The current mainstream CO\u003csub\u003e2\u003c/sub\u003e reduction strategies include biological fixation \u003csup\u003e[\u003cspan additionalcitationids=\"CR6\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e, chemical adsorption \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e, thermal catalysis \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/sup\u003e and geological sequestration \u003csup\u003e[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e, etc: Biological fixation relies on photosynthesis by plants or microbes to assimilate CO\u003csub\u003e2\u003c/sub\u003e; however, it suffers from low sequestration efficiency, long cycles, and environmental limitations; Although chemisorption techniques (such as amine washing \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e, metal-organic framework materials \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e) can achieve efficient capture, However, the energy consumption of adsorbent regeneration is high and the cycle stability is poor.Although thermocatalytic CO\u003csub\u003e2\u003c/sub\u003e reduction offers a wide product spectrum, simple equipment, and low cost\u0026mdash;making it attractive for large-scale deployment\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e\u0026mdash;its long-term feasibility remains contentious. Geological storage of CO\u003csub\u003e2\u003c/sub\u003e needs to be compressed and injected into deep geological structures, but there is a risk of leakage and long-term monitoring problems.In contrast, electrocatalytic CO\u003csub\u003e2\u003c/sub\u003e reduction (eCO\u003csub\u003e2\u003c/sub\u003eRR) technology is considered a key path to achieving carbon neutrality by driving the conversion of CO\u003csub\u003e2\u003c/sub\u003e into high value-added chemicals (e.g., CO \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]\u003c/sup\u003e, syngas \u003csup\u003e[\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e, hydrocarbons \u003csup\u003e[\u003cspan additionalcitationids=\"CR25\" citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e, hydrocarbon derivatives \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e, etc.), which have the advantages of carbon recycling and energy storage \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e.However, eCO\u003csub\u003e2\u003c/sub\u003eRR faces the dual challenge of the high stability of CO\u003csub\u003e2\u003c/sub\u003e molecules and competition from the side reaction of hydrogen evolution (HER),Phthalocyanine compounds have advantages such as easy synthesis, low cost, and adjustable structure, making them ideal catalytic materials for eCO\u003csub\u003e2\u003c/sub\u003eRR.Among the polyphthalocyanine materials with metal centers such as iron \u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e, cobalt \u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e, nickel \u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e, and copper \u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e, NiPPc stands out with its unique M-N\u003csub\u003e4\u003c/sub\u003e coordination structure and adjustable electronic properties, but it still has problems such as overly strong intermediate adsorption and slow reaction kinetics\u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/sup\u003e. This leads to insufficient low-potential activity and intensifies the hydrogen evolution side reaction.To overcome this technical bottleneck, Cu, with its precise *COOH intermediate adsorption regulation characteristics, can dynamically balance the CO desorption kinetics and the C-C coupling reaction process \u003csup\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/sup\u003e, demonstrating a synergistic effect in achieving the directional synthesis of multi-carbon products and the regulation of syngas components \u003csup\u003e[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e, \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]\u003c/sup\u003e.Based on the above findings, this study innovatively proposes to directionally regulate the electronic structure characteristics of NiPPc materials through copper ion doping strategies and reconstruct the coordination configuration of their surface catalytic sites.\u003c/p\u003e\u003cp\u003eThe experiment precisely constructed the gradient Cu-doped NiPPc: Cu catalyst by solvothermal method, and systematically studied the influence of doping amount on the CO\u003csub\u003e2\u003c/sub\u003e reduction performance.Cu-ion doping engineering effectively modulated both the geometric structure and electronic properties of the active sites, leading to enhanced catalytic activity and tunable product selectivity. This provides a solid theoretical basis and practical solutions for designing efficient CO\u003csub\u003e2\u003c/sub\u003eRR catalysts.\u003c/p\u003e"},{"header":"Experimental","content":"\u003ch2\u003eMaterials\u003c/h2\u003e\u003cp\u003eThe Nickel acetate tetrahydrate (Ni(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO), copper acetate monohydrate (Cu(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO), 1,2,4,5-tetracyanobenzene (C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e) and Nafion were supplied by Shanghai Maikelin Bioengineering Technology Co., Ltd. Ethanol (CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eOH), sulfuric acid (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) and hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) were obtained from Tianjin Yongda Chemical Reagent Co., Ltd. Potassium bicarbonate (KHCO\u003csub\u003e3\u003c/sub\u003e) was provided by Shanghai Aladdin Biochemical Technology Co., Ltd.\u003c/p\u003e\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003ePreparation of electrocatalysts\u003c/h2\u003e\u003cp\u003eUsing the solvothermal method, the specific experimental process is as follows:\u003c/p\u003e\u003cp\u003eNi(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO, C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e, and Cu(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO were weighed in the desired ratios and sequentially added to 35 mL of ethanol.The mixture was stirred at 500 rpm for 30 min, sonicated for 1 h, then heated in an autoclave at 180\u0026deg;C for 24 h. After naturally cooling to room temperature, centrifuge wash with anhydrous ethanol (8000 rpm, 5 min, repeated 3 times), the obtained precipitate is dried in a vacuum oven at 80\u0026deg;C for 12 hours, and after grinding, NiPPc: Cu powder is obtained.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eInstallation and testing of electrochemical equipment\u003c/h3\u003e\n\u003cp\u003eWorking-electrode fabrication: Carbon paper (1 cm \u0026times; 1.5 cm) was calcined at 200\u0026deg;C for 3 h under Ar. A catalyst ink (4 mg catalyst, 960 \u0026micro;L EtOH, 40 \u0026micro;L Nafion) was sonicated for 30 min; 100 \u0026micro;L of the ink was drop-cast onto 1 cm\u0026sup2; of the carbon paper in two aliquots and dried under UV.\u003c/p\u003e\u003cp\u003eMembrane pretreatment: Nafion 115 was boiled in deionized water (30 min), treated with 3% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e at 80\u0026deg;C (1 h), rinsed again in boiling water (30 min), immersed in 1 M H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e (30 min), and finally washed in boiling water (30 min) before storage in deionized water.\u003c/p\u003e\u003cp\u003eElectrolyte: 0.5 M KHCO\u003csub\u003e3\u003c/sub\u003e (10.012 g in 200 mL H\u003csub\u003e2\u003c/sub\u003eO).\u003c/p\u003e\u003cp\u003eElectrolytic cell assembly:The pretreated membrane was clamped between the two chambers, each filled with 30 mL electrolyte. CO\u003csub\u003e2\u003c/sub\u003e was supplied to the catholyte at 10 mL min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 30 min. An Ag/AgCl electrode and Pt foil served as reference and counter electrodes,The test potential was converted using the formula E(vs.RHE) = E(vs.Ag/AgCl) + 0.197 + 0.0592 × pH (1).Using linear sweep voltammetry (LSV) to analyze the initial potential and current density of the sample to evaluate the performance of the catalyst.Electrochemical impedance spectroscopy (EIS) obtains the reaction kinetics of the materials.The electrochemical active surface area (ECSA) was calculated using the formula ECSA = Cdl/Cs (2), which reflects the accommodation of catalytic sites.By combining electrochemical testing with gas chromatography analysis, the Faradaic efficiency is calculated using the I-t data through formula \n\u003cimg src=\"data:image/png;base64,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\" width=\"228\" height=\"55\"\u003e (3).By calculating the CO partial current density through equation \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\text{j}}_{\\text{C}\\text{O}}={\\text{j}}_{\\text{总}}\\times\\:{\\text{x}}_{\\text{C}\\text{O}}\\)\u003c/span\u003e\u003c/span\u003e(4) and analyzing the CO/H\u003csub\u003e2\u003c/sub\u003e ratio, the CO\u003csub\u003e2\u003c/sub\u003e reduction efficiency, product selectivity and syngas tunability.\u003c/p\u003e\n\u003ch3\u003ePhysical characterization\u003c/h3\u003e\n\u003cp\u003eThis study systematically analyzes the characteristics of samples through multi-dimensional representation technology: Characterization and analysis of the sample's phase and crystal structure using X-ray diffraction (XRD, D/MAX2500PC); Using a Fourier Transform Infrared Spectrometer (FT-IR, VERTEX70) to accurately analyze molecular structure and identification; At the same time, the chemical bond vibrations and chemical bond information were obtained using the micro-Raman spectrometer (DXR);Observe the morphological characteristics of the catalyst nanoscale structure through transmission electron microscopy (TEM, HT-7800) and conduct elemental mapping analysis;Further use of X-ray photoelectron spectroscopy (XPS, Thermo Kalpha) to deeply analyze the chemical state and elemental valence state of the material surface.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003eThe effect of Cu ion doping amount on the structure of NiPPc: Cu\u003c/h2\u003e\u003cp\u003eUsing nickel content as a benchmark, copper ions are introduced into the system in mass proportions, with the amounts set at 10%, 30%, 50%, 70%, and 90% of the nickel content.The series of materials prepared are sequentially named as 10 wt% NiPPc: Cu, 30 wt% NiPPc: Cu, 50 wt% NiPPc: Cu, 70 wt% NiPPc: Cu, and 90 wt% NiPPc: Cu. XRD patterns (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e) show that the polyphthalocyanine peak at ~\u0026thinsp;27\u0026deg; weakens and broadens upon initial Cu incorporation, indicating a loss of crystallinity. Within the NiPPc:Cu series, however, the ~\u0026thinsp;27\u0026deg; reflection gradually regains intensity as the Cu level increases, pointing to a partial restoration of structural order.\u003c/p\u003e\u003cp\u003eFT-IR spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) show that the phthalocyanine-ring vibrations are more intense for 30 wt % NiPPc:Cu than for pristine NiPPc; the intensity remains above the NiPPc level up to 90 wt % Cu, indicating that \u0026ge;\u0026thinsp;30 wt % Cu promotes phthalocyanine formation, whereas 10 wt % Cu suppresses it. The terminal C\u0026thinsp;\u0026equiv;\u0026thinsp;N stretch at 2 231 cm⁻\u0026sup1; also gains intensity at 30 wt % Cu, confirming enhanced C\u0026ndash;N bond formation. Raman spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e2\u003c/span\u003eb) display a weak but consistent metal-phthalocyanine band at ~\u0026thinsp;1 560 cm⁻\u0026sup1; across all Cu loadings, corroborating the FT-IR conclusions.\u003c/p\u003e\u003cp\u003eTEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003ea,b) reveals uniform\u0026thinsp;~\u0026thinsp;500 nm spheres whose morphology is preserved after Cu introduction. Elemental maps (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003ec\u0026ndash;f) show homogeneous distributions of Ni, Cu, N and C, evidencing successful NiPPc:Cu formation. The EDS spectrum (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e) corroborates the uniform incorporation of Cu within the NiPPc matrix.\u003c/p\u003e\u003cp\u003eThe survey XPS scan (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ea) confirms the presence of Ni, Cu, N and C, verifying NiPPc:Cu formation. The Cu 2p region (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb) exhibits broad, poorly fitted peaks at 934.98 eV (Cu 2p\u003csub\u003e3/2\u003c/sub\u003e) and 955.27 eV (Cu 2p\u003csub\u003e1/2\u003c/sub\u003e), indicating that Cu is predominantly Cu(II) with a minor Cu(I) contribution, but is not fully incorporated into the phthalocyanine lattice. Ni 2p and C 1s spectra (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003eb,c) show negligible shifts, whereas the N 1s signal (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003ed) reveals a marked weakening of the Ni\u0026ndash;N bond, evidencing electronic perturbation of the macrocycle upon Cu introduction.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003eThe effect of Cu ion doping amount on the CO\u003csub\u003e2\u003c/sub\u003e reduction performance of NiPPc: Cu\u003c/h2\u003e\u003cp\u003eActivity tests (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003ea) show that 10 wt % Cu improves low-overpotential stability through structural uniformity, whereas 50 wt % Cu tunes *COOH adsorption via Cu\u0026ndash;N₄ sites; together they optimise overall performance. Between \u0026minus;\u0026thinsp;0.6 and \u0026minus;\u0026thinsp;0.9 V vs. RHE the doped catalysts deliver lower current than pristine NiPPc, but beyond ~\u0026thinsp;1 V overpotential all Cu-containing samples outperform the parent material. In the 10\u0026ndash;15 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e window the potentials required decrease in the order 30\u0026thinsp;\u0026gt;\u0026thinsp;10\u0026thinsp;\u0026gt;\u0026thinsp;90\u0026thinsp;\u0026gt;\u0026thinsp;50\u0026thinsp;\u0026gt;\u0026thinsp;70 wt % NiPPc: Cu, while at higher densities the polarisation curves converge. EIS (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) reveals larger charge-transfer resistance for the doped electrodes, indicating compromised kinetics.\u003c/p\u003e\u003cp\u003eAs seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e, the low scanning speed has little effect on the CV of NiPPc:Cu, as derived from Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e(f) based on Figs.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e (a-e). Figure\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e (f) shows that the double layer capacitance of 10 wt% NiPPc: Cu, 50 wt% NiPPc: Cu, and 70 wt% NiPPc: Cu is higher than that of NiPPc (0.809429 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e), which are 2.76 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, 3.25 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, and 1.02 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, respectively;But 30 wt% NiPPc: Cu (0.163143 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) and 90 wt% NiPPc: Cu (0.270214 mF\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e) are lower than NiPPc.\u003c/p\u003e\u003cp\u003eTo investigate the effect of doping Cu on the stability of NiPPc, I-t tests were conducted. As can be seen from Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e8\u003c/span\u003e, at a potential of \u0026minus;\u0026thinsp;0.8 V vs. RHE shows that 10 wt % NiPPc:Cu sustains 5 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, whereas NiPPc and all other Cu-doped variants deliver only\u0026thinsp;~\u0026thinsp;2.5 mA cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e, evidencing enhanced low-potential activity with light Cu loading. Over 3 600 s the current density of 10 wt % NiPPc: Cu remains virtually unchanged, confirming superior stability.\u003c/p\u003e\u003cp\u003eWhen the doping amount of Cu is 10% and 90%, the trend of the catalyst's selectivity to CO is consistent, both first increasing and then decreasing.At\u0026minus;0.8 V (vs.RHE), the selectivity for CO of 90 wt% NiPPc: Cu was lower than that of 10 wt% NiPPc: Cu.However, in the range of\u0026minus;0.9 to\u0026minus;1.1 V (vs. RHE), the 90 wt% NiPPc: Cu has a higher selectivity for CO.For 30 wt% NiPPc: Cu, at potentials of\u0026minus;0.8 V and\u0026minus;0.9 V (vs.RHE), the Faradaic efficiency for CO is about 50%, with a CO to H\u003csub\u003e2\u003c/sub\u003e ratio of 1:1 (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e(d)).When the amount of Cu doping increases to 50 wt% and 70 wt%, the catalyst shows a significant enhancement in selectivity for CO in the high potential range (\u0026minus;0.8 to\u0026minus;1.1 V (vs.RHE) ).The CO faradaic efficiency of 50 wt% NiPPc: Cu can reach over 65%, and can be as high as about 95% at\u0026minus;1.0 V (vs. RHE), achieving a jump in CO selectivity at high potentials (Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a) ).The performance is better than the recently reported M-N\u003csub\u003e4\u003c/sub\u003e type catalyst \u003csup\u003e[\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]\u003c/sup\u003e;The CO faradaic efficiency of 70 wt% NiPPc: Cu can be stably maintained at 80% at\u0026minus;0.8 to\u0026minus;1.0 V (vs. RHE).\u003c/p\u003e\u003cp\u003eOverall, for the single product CO, 50 wt% NiPPc: Cu exhibits excellent CO\u003csub\u003e2\u003c/sub\u003e reduction performance.The CO Faradaic efficiency of 30 wt% NiPPc: Cu is about 50%, at which point the ratio of CO to H\u003csub\u003e2\u003c/sub\u003e was 1:1, allowing for precise control of the composition ratio of synthesis gas.At a lower potential (\u0026minus;0.8V (vs.RHE) ), 10 wt% NiPPc: Cu exhibits a CO partial current density of approximately 5 mA\u0026middot;cm\u0026thinsp;\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e9\u003c/span\u003e (a) ),At the same time, the ratio of CO to H\u003csub\u003e2\u003c/sub\u003e is approximately 10, which can achieve a high level of CO\u003csub\u003e2\u003c/sub\u003e reduction performance. Therefore, 10 wt% NiPPc: Cu is the optimal catalyst choice in this case.\u003c/p\u003e\u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis study successfully constructed a copper ion gradient-doped nickel-based phthalocyanine complex (NiPPc: Cu) electrocatalyst through a heterogeneous atom doping strategy using a solvent thermal method.Through systematic and in-depth research, the effect of different copper ion doping levels on the structure and performance of the catalyst has been comprehensively explored.Systematic research indicates that high amounts of Cu contribute to the formation of phthalocyanine structures.In terms of performance, different doping amounts have varying effects on the catalyst activity, stability, and product selectivity.Low doping concentration improves stability, while high doping concentration regulates the adsorption pathways of intermediates.In terms of product selectivity, a 30 wt% can adjust the ratio of CO to H\u003csub\u003e2\u003c/sub\u003e to 1:1, while 50 wt% and 70 wt% enhance CO selectivity at high potentials.For a single CO product, 50 wt% NiPPc: Cu performs better.Synthesis gas selects 30 wt% NiPPc: Cu;Under low potential, the best CO\u003csub\u003e2\u003c/sub\u003e reduction performance was with 10 wt% NiPPc: Cu.This work delivers both theoretical insights and practical protocols for designing high-performance CO\u003csub\u003e2\u003c/sub\u003eRR catalysts, representing a significant advance toward the industrialization of electrocatalytic carbon-recycling technologies.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003eAbbreviations\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003efull name\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003eCO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 259px;\"\u003e\n \u003cp\u003ecarbon monoxide\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003ecarbon dioxide\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eCu(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;H\u003csub\u003e2\u003c/sub\u003eO)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003ecopper(II) acetate monohydrate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eEtOH/CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003eOH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eethanol\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003ehydrogen\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003ehydrogen peroxide\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003esulfuric acid\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eKHCO\u003csub\u003e3\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003epotassium bicarbonate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eNi(CH\u003csub\u003e3\u003c/sub\u003eCOO)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003enickel(II) acetate tetrahydrate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eNiPPc\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003enickel polyphthalocyanine\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eNiPPc: Cu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eCu-doped nickel polyphthalocyanine\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eNation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eperfluorosulfonic acid ionomer\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eC\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003e1,2,4,5-tetracyanobenzene\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003e*COOH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003ecarboxyl intermediate\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eCO/H\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003esyngas\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003eM\u0026ndash;N\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 259px;\"\u003e\n \u003cp\u003emetal\u0026ndash;nitrogen\u003csub\u003e4\u003c/sub\u003e coordination\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cem\u003eEthics and Consent to Participate\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable. This work does not involve human participants, human data, human tissue, or animals.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eConsent for Publication\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAll authors hereby solemnly declare that they have thoroughly reviewed and hereby affirmatively consent to submit this manuscript entitled \u0026quot;Effects of Cu Doping on NiPPc electrocatalysts for CO\u003csub\u003e2\u003c/sub\u003e Electrocatalytic Reduction\u0026quot; for publication in\u0026nbsp;Catalysis Letters. Additionally, they commit to fully complying with all procedures stipulated by the journal\u0026apos;s publication protocol and strictly adhering to regulations governing copyright transfer.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eCompeting Interest\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAuthor Contribution\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eH.N.C. and C.Y.W. conceived the project, designed the experiments and supervised the study,wrote the main manuscript. Z.H.W, W.K.P. and J.Y.H. \u0026nbsp;systematically integrated the research background, methodology and findings, and finalized the core discussion.S.T.T. and Z.X.S. prepared all figures and tables, transforming experimental data into clear visual representations with professional graphing and statistical tools.Y.L. performed the electrocatalytic tests, materials characterization and data collection, ensuring reproducibility and reliability.All authors critically reviewed the draft, provided feedback on academic rigor and content accuracy, and approved the final version of the paper.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFunding\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge the support of the National Natural Science Foundation of China (Grant No. 5187209) and the Tangshan Basic Research Fund Project (No. 23130210E)\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp;Availability of data and materials\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eExperimental data and materials used in this study are available upon reasonable request from the corresponding author.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eAcknowledgments\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eWe thank the School of Materials Science and Engineering, North China University of Science and Technology, for the technical support in characterization testing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eCui CY, Sa RJ, Hong ZX (\u003cstrong\u003e2020\u003c/strong\u003e) Ionic-Liquid-Modified Click-Based Porous Organic Polymers for Controlling Capture and Catalytic Conversion of CO2. \u003cem\u003eCHEMSUSCHEM \u003c/em\u003ehttps://10.1002/cssc.201902715\u003c/li\u003e\n\u003cli\u003eDu J, Ouyang H, Tan B (\u003cstrong\u003e2021\u003c/strong\u003e) Porous Organic Polymers for Catalytic Conversion of Carbon Dioxide. \u003cem\u003eCHEMISTRY-AN ASIAN JOURNAL 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Products. \u003cem\u003eACS CATALYSIS \u003c/em\u003ehttps://10.1021/acscatal.3c01439\u003c/li\u003e\n\u003cli\u003eZhu CY, Geng Y, Yao XH (\u003cstrong\u003e2023\u003c/strong\u003e) Fascinating Electrocatalysts with Dispersed Di-Metals in MN3-M\u0026apos;N4 Moiety as Two Active Sites Separately for N2 and CO2 Reduction Reactions and Jointly for C-N Coupling and Urea Production. \u003cem\u003eSMALL METHODS \u003c/em\u003ehttps://10.1002/smtd.202201331\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Cu ion doping, NiPPc, Electrocatalyst, CO2 reduction, Electrochemical properties","lastPublishedDoi":"10.21203/rs.3.rs-7803669/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7803669/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe climate crisis caused by excessive carbon dioxide (CO\u003csub\u003e2\u003c/sub\u003e) emissions urgently call for efficient electrocatalytic reduction technology to convert CO\u003csub\u003e2\u003c/sub\u003e into high value-added products. In this study, nickel polyphthalocyanine (NiPPc) electrocatalysts with different copper (Cu) doping amounts (10-90wt%) were prepared by solvothermal method, Combining X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and other characterization and electrochemical testing, it is found that: Doping with 10 wt% Cu significantly enhanced catalytic activity, achieving a current density of 325 mA\u0026middot;cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e at -0.6 V (vs. RHE)\u0026mdash;2.8 times that of the undoped sample;50 wt% Cu doping optimized the Cu\u0026ndash;N\u003csub\u003e4\u003c/sub\u003e active sites, yielding a carbon monoxide (CO) Faraday efficiency of up to 95% at -1.0 V; 30 wt% Cu-doped catalyst can generate CO:H\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;1:1 syngas, A controllable catalyst design strategy is provided for CO\u003csub\u003e2\u003c/sub\u003e electrocatalytic reduction.\u003c/p\u003e","manuscriptTitle":"Effects of Cu Doping on NiPPc electrocatalysts for CO 2 Electrocatalytic Reduction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-27 11:33:23","doi":"10.21203/rs.3.rs-7803669/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-11-24T15:49:37+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-24T04:29:46+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-11-04T23:33:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"20715588243245231309675825616467472158","date":"2025-11-02T00:36:38+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"273324575515173538689215245805825722271","date":"2025-10-18T01:21:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-12T22:19:30+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-10-08T09:38:35+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-08T09:38:27+00:00","index":"","fulltext":""},{"type":"submitted","content":"Catalysis Letters","date":"2025-10-08T03:33:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"catalysis-letters","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Catalysis Letters](https://link.springer.com/journal/10562)","snPcode":"10562","submissionUrl":"https://submission.springernature.com/new-submission/10562/3","title":"Catalysis Letters","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e2167e8f-4c5a-4535-b892-5d848698d6da","owner":[],"postedDate":"October 27th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-29T15:53:07+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-27 11:33:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7803669","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7803669","identity":"rs-7803669","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}