Electrolysis water catalyst, and preparation method and application thereof
By constructing a CoP/Fe2O3 hierarchical heterostructure on a nickel foam substrate, the electronic structure and active sites of the catalyst are controlled, solving the problems of high cost of precious metal catalysts and insufficient performance of cobalt-based oxides. This achieves low-cost and high-efficiency water electrolysis performance, especially exhibiting excellent HER and OER activities under alkaline conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV
- Filing Date
- 2026-05-14
- Publication Date
- 2026-07-07
AI Technical Summary
Existing precious metal catalysts suffer from high cost, limited resources, and weak HER performance in water electrolysis. Cobalt-based oxides have insufficient conductivity and limited interfacial charge transport capacity in water electrolysis, making it difficult to meet the requirements for efficient overall water electrolysis.
Using nickel foam as a conductive framework and cobalt molybdenum hydrate as a substrate, a CoP composite structure is formed through phosphating treatment, and Fe2O3 is deposited using ALD technology. Combined with in-situ electrochemical activation treatment, the local electronic structure and active sites of the catalyst are regulated to form a multi-level heterostructure synergistically regulated by CoP/Fe2O3.
It significantly improves HER performance and also has excellent OER activity, achieving low-cost and high-efficiency overall water electrolysis performance. The catalyst has a HER overpotential as low as 23mV, an OER overpotential as low as 180mV, and a total water electrolysis voltage as low as 1.44V under alkaline conditions, and has good long-term stability.
Smart Images
Figure CN122344748A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water electrolysis catalyst preparation technology, specifically relating to a water electrolysis catalyst, its preparation method, and its application. Background Technology
[0002] With the massive consumption of fossil fuels and the increasing prominence of environmental pollution, the development of clean, efficient, and sustainable energy has become an important research direction. Hydrogen energy, due to its high energy density and clean, pollution-free nature, is considered a clean energy source with great application potential. Water electrolysis is an important technological route for producing green hydrogen; however, both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have high reaction energy barriers and overpotentials, resulting in high overall energy consumption. Therefore, developing low-cost, highly active bifunctional electrocatalysts that combine the performance of HER and OER is of great significance.
[0003] Currently, noble metal catalysts such as Pt / C, RuO2, and IrO2 exhibit excellent water electrolysis performance, but their high cost and limited resources restrict their large-scale application. In contrast, cobalt-based oxides have attracted widespread attention in the field of water electrolysis due to their abundant resources and lower cost, especially their good OER performance. However, they still suffer from insufficient conductivity, limited interfacial charge transport capacity, and low utilization of active sites, resulting in weak HER performance and difficulty in meeting the requirements for efficient overall water electrolysis. To improve their HER performance, elemental doping and interface engineering are commonly used to improve the electronic structure and surface reaction behavior of cobalt-based oxides. Summary of the Invention
[0004] This invention provides a water electrolysis catalyst, its preparation method, and its application. Using nickel foam as a conductive framework and cobalt-molybdenum hydrate as a substrate precursor, a CoP-containing composite structure is formed through phosphating. Fe2O3 is then deposited on its surface using atomic layer deposition (ALD) technology. Further combined with in-situ electrochemical activation treatment, the catalyst's local electronic structure is regulated, and the intrinsic activity of active sites is enhanced, thereby significantly improving HER performance and exhibiting excellent OER activity, achieving highly efficient overall water electrolysis performance.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: An electrolytic water catalyst is a cobalt-based oxide synergistically regulated by CoP / Fe2O3, which has a multi-level heterogeneous structure and a nanosheet-like morphology on the surface. It is based on nickel foam, with a cobalt molybdate hydrate layer loaded on the surface. After phosphating, a CoP-containing composite structure is formed. The surface of the composite structure is further loaded with Fe2O3 by ALD technology and then subjected to in-situ electrochemical activation treatment.
[0006] A method for preparing a water electrolysis catalyst includes the following steps: Preparation of cobalt-based precursors on conductive substrates; The cobalt-based precursor is subjected to phosphating treatment to form a phosphide layer as an activation induction layer; In-situ electrochemical activation was performed to obtain a water electrolysis catalyst.
[0007] In the steps described above, an iron oxide layer can be deposited on the surface of the phosphide layer as a synergistic enhancement layer before activation. The phosphide layer formed by phosphating can regulate the local electronic environment on the surface of cobalt-molybdenum hydrate, thereby improving its performance during in-situ electrochemical activation. Further deposition of the iron oxide layer can form an interface synergistic effect with the phosphide layer, altering the electronic structure around the phosphide and enhancing the charge redistribution and structural reconstruction processes during activation. Therefore, after the deposition of the iron oxide layer, in-situ electrochemical activation of the entire iron oxide / phosphide / cobalt-molybdenum hydrate composite catalyst can further improve its catalytic performance.
[0008] Preferably, the preparation of a cobalt-based precursor on a conductive substrate includes the following steps: dissolving a cobalt source and a molybdenum source in a solvent at a molar ratio of 1-2:1 to form a reaction solution; immersing the conductive substrate in the reaction solution to perform a hydrothermal reaction, thereby growing the cobalt-based precursor on the surface of the conductive substrate.
[0009] The cobalt source is cobalt nitrate hexahydrate, and the molybdenum source is sodium phosphomolybdate; the hydrothermal reaction temperature is 180-200℃, and the time is 5-8h.
[0010] Preferably, the phosphating treatment includes the following steps: placing hypophosphite as a phosphorus source upstream of the reaction vessel, placing the cobalt-based precursor downstream, and performing phosphating under inert gas protection to form a phosphide layer on the surface of the cobalt-based precursor.
[0011] The phosphating treatment is performed at a temperature of 300-350℃, with a heating rate of 2℃ / min. -1 The time is 1-2 hours.
[0012] Preferably, the deposited iron oxide layer is deposited using atomic layer deposition (ALD) technology; the deposition is performed using ozone-assisted ALD, the precursor is ferrocene, the source temperature is 100°C, the deposition temperature is 180-200°C, and the number of deposition cycles is 50-200.
[0013] Preferably, the in-situ electrochemical activation treatment includes the following steps: electrochemically treating the structure after depositing the iron oxide layer in a constant current mode to obtain the activated water electrolysis catalyst; wherein the current density is 10 mA cm⁻¹. -2 The activation time is 2-5 hours.
[0014] The present invention also provides a catalyst prepared by the above method, or the application of the above water electrolysis catalyst in water electrolysis.
[0015] Beneficial Effects: This invention provides a water electrolysis catalyst, its preparation method, and its application. Using cobalt-molybdenum acid hydrate as a substrate, a phosphide active layer is constructed via phosphating, and an iron oxide layer is loaded using ALD technology, forming a multi-level heterogeneous structure of cobalt-molybdenum acid hydrate co-supported by iron oxide and phosphide. The phosphide layer alters the local electronic environment on the surface of the cobalt-molybdenum acid hydrate, promoting surface charge redistribution and Co-O-Mo bond breaking during in-situ electrochemical activation, reducing the coordination number of Co atoms, and inducing spin polarization, thereby optimizing the adsorption strength of hydrogen intermediates and improving the HER reaction activity. Further loading of iron oxide and the phosphide form an interfacial coupling, enhancing the electronic regulation and structural reconstruction induced by the phosphide layer, further improving the intrinsic catalytic activity of the active sites. Based on these structural advantages, the catalyst exhibits excellent HER performance under alkaline conditions, reaching 10 mA cm⁻¹. -2 The HER overpotential is as low as 23 mV at current density, while exhibiting a low overpotential of 180 mV in OER. The total water splitting voltage is as low as 1.44 V, and it has good long-term stability. Moreover, the catalyst of this invention adopts a non-precious metal system, which is inexpensive. Combined with a three-dimensional nickel foam conductive network, it is beneficial to gas release and mass transfer processes, and has good application prospects in the field of water electrolysis. Attached Figure Description
[0016] Figure 1 The XRD patterns of the CMOH / NF, CoP@CMOH / NF, Fe2O3@CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF-A catalysts synthesized and prepared in the embodiments of the present invention are shown. Figure 2 The image shows a SEM image of the Fe2O3@CoP@CMOH / NF catalyst synthesized and prepared in the embodiments of the present invention. Figure 3 This is a SEM image of the Fe2O3@CoP@CMOH / NF-A catalyst synthesized and prepared in the embodiments of the present invention; Figure 4 Electrochemical performance diagrams of the CMOH / NF, CoP@CMOH / NF, CoP@CMOH / NF-A, Fe2O3@CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF-A catalysts HER synthesized and prepared in the embodiments of the present invention: (a) is the LSV curve, and (b) is the Tafel slope curve; Figure 5 The Fe2O3@CoP@CMOH / NF-A catalyst synthesized in this embodiment of the invention was prepared at 10 mA cm⁻¹. -2Long-term stability curves of HER at current density; Figure 6 The above is a bar chart showing the TOF values of the CoP@CMOH / NF, CoP@CMOH / NF-A, Fe2O3@CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF-A catalysts synthesized and prepared in the embodiments of the present invention. Figure 7 Electrochemical performance diagrams of the CMOH / NF, CoP@CMOH / NF, CoP@CMOH / NF, Fe2O3@CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF catalysts OER synthesized and prepared in the embodiments of the present invention: (a) is the LSV curve, (b) is the Tafel slope curve; Figure 8 The Fe2O3@CoP@CMOH / NF catalyst synthesized in this embodiment of the invention was tested at 10 mA cm⁻¹. -2 Long-term stability curves of OER at current density; Figure 9 The following are electrochemical performance graphs of the Fe2O3@CoP@CMOH / NF catalyst synthesized in the embodiments of the present invention for the complete water splitting: (a) is the LSV curve, and (b) is the long-term stability curve. Detailed Implementation
[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments: In the following examples and figures, CMOH represents cobalt molybdate hydrate, NF represents nickel foam, and A represents the sample after in-situ electrochemical activation treatment.
[0018] Example 1:
[0019] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide water electrolysis catalyst, comprising the following steps: (1) Cut the nickel foam into 1 cm × 4 cm sizes, and clean it with anhydrous ethanol and deionized water for 30 min each. After cleaning, dry it at 60°C for later use. (2) The above-mentioned nickel foam was ultrasonically treated in 3M HCl solution for 15 min, and then ultrasonically cleaned in deionized water and anhydrous ethanol for 30 min respectively. After cleaning, it was dried at 60°C to obtain the pretreated nickel foam substrate. (3) 1 mmol of Co(NO3)2·9H2O and 1 mmol of Na3PO4·12MoO3·xH2O were added to 40 mL of deionized water and stirred for 2 h to form a homogeneous solution. Then, the pretreated nickel foam was immersed in the solution and transferred to a hydrothermal reactor and reacted at 180 °C for 6 h. After the reaction was completed, the sample was taken out, rinsed with deionized water and dried at 60 °C to obtain the CMOH / NF catalyst. (4) The CMOH / NF catalyst was placed downstream of a tube furnace, and 0.5g of NaH2PO2 was placed upstream. Gas-phase phosphating was carried out under Ar atmosphere protection at a temperature of 350℃ for 1h. After the reaction was completed, the furnace was cooled to obtain CoP@CMOH / NF catalyst. (5) Fe2O3 film was deposited on the CoP@CMOH / NF substrate prepared in step (4) using ALD technology. The deposition was ozone-assisted ALD, the deposition temperature was 180℃, the precursor was ferrocene, the source temperature was 100℃, and the reactant was ozone. The deposition cycle included a 2s ferrocene pulse, a 5s cleaning pulse, a 10s ozone pulse and a 12s cleaning pulse, and the number of cycles was 100. The cleaning gas and the carrier gas were both high-purity N2 (99.999%), and the Fe2O3@CoP@CMOH / NF catalyst was obtained. (6) The CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF catalysts were subjected to in-situ electrochemical activation using a constant current method with a current density of 10 mA cm⁻¹. -2 The activation time was 2 hours, resulting in CoP@CMOH / NF-A and Fe2O3@CoP@CMOH / NF-A catalysts.
[0020] Example 2:
[0021] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide water electrolysis catalyst as shown in Example 1. The difference is that in step (3), 2 mmol of Co(NO3)2·9H2O and 1 mmol of Na3PO4·12MoO3·xH2O are added to 40 mL of deionized water, and the remaining conditions are the same as in Example 1, to obtain the CMOH / NF catalyst.
[0022] Example 3:
[0023] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide water electrolysis catalyst as shown in Example 1. The difference is that in step (3), the hydrothermal temperature is 200℃, and the other conditions are the same as in Example 1, thus obtaining the CMOH / NF catalyst.
[0024] Example 4:
[0025] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide electrolysis water catalyst as shown in Example 1. The difference is that in step (4), the phosphating temperature is 300℃, and the other conditions are the same as in Example 1, thus obtaining the CoP@CMOH / NF catalyst.
[0026] Example 5:
[0027] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide water electrolysis catalyst as shown in Example 1. The difference is that in step (5), the ALD deposition temperature is 200℃, and the other conditions are the same as in Example 1, to obtain the Fe2O3@CoP@CMOH / NF catalyst.
[0028] Example 6:
[0029] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide electrolysis water catalyst as shown in Example 1. The difference is that in step (5), the number of Fe2O3 cycles deposited by ALD is 50 cycles, and the other conditions are the same as in Example 1, thus obtaining the Fe2O3@CoP@CMOH / NF catalyst.
[0030] Example 7:
[0031] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide electrolysis water catalyst as shown in Example 1. The difference is that in step (5), the number of Fe2O3 cycles deposited by ALD is 200 cycles, and the other conditions are the same as in Example 1, thus obtaining the Fe2O3@CoP@CMOH / NF catalyst.
[0032] Example 8:
[0033] This embodiment provides a method for preparing a CoP / Fe2O3 synergistically regulated cobalt-based oxide water electrolysis catalyst as shown in Example 1. The difference is that in step (6), the activation time is 5h, and the other conditions are the same as in Example 1, to obtain CoP@CMOH / NF-A and Fe2O3@CoP@CMOH / NF-A catalysts.
[0034] like Figure 1 As shown, the main phase of the CMOH / NF catalyst prepared in the above examples is Co. 1.2 MoO 4.2• 1,3H₂O, corresponding to standard card PDF#14-0087; Ni metal diffraction peaks were also detected on the nickel foam substrate, corresponding to PDF#04-0850. After loading with CoP and 100 cycles of Fe₂O₃ as in Example 1, the overall diffraction peaks of the material showed a slight shift. Further, after in-situ electrochemical activation treatment, Co… 1.2 MoO 4.2 The disappearance of the diffraction peaks of the 1,3H2O phase indicates that the material has undergone structural reconstruction.
[0035] like Figure 2 As shown, the Fe2O3@CoP@CMOH / NF catalyst prepared in Example 1 has a columnar structure with an average diameter of about 7.6 μm, a relatively smooth surface, and a small amount of particles attached to it.
[0036] like Figure 3 As shown, the Fe2O3@CoP@CMOH / NF-A catalyst in Example 1, after in-situ electrochemical activation treatment, still maintains the columnar morphology, but the surface transforms into a nanosheet structure at the nanoscale, with a significant increase in roughness. This is beneficial for increasing the specific surface area and promoting the adsorption of reactants, thereby enhancing HER kinetics.
[0037] like Figure 4 As shown, using the catalysts CMOH / NF, CoP@CMOH / NF, CoP@CMOH / NF-A, Fe2O3@CoP@CMOH / NF, and Fe2O3@CoP@CMOH / NF-A from Example 1 as the working electrode, a graphite rod as the counter electrode, and Hg / HgO as the reference electrode, a three-electrode system was constructed in 1M KOH electrolyte solution for electrochemical performance testing. The results are as follows. Figure 4 As shown. Among them, CMOH / NF, CoP@CMOH / NF, CoP@CMOH / NF-A, Fe2O3@CoP@CMOH / NF and Fe2O3@CoP@CMOH / NF-A catalysts were used at 10 mA cm⁻¹. -2 The overpotentials of HER at different current densities were 109 mV, 123 mV, 83 mV, 70 mV, and 23 mV, respectively, and the Tafel slopes were 159.92 mV dec. -1 252.17 mV dec -1 139.57mV dec -1 174.01mV dec -1 50.06mV dec -1 , Figure 5 The constant current test results showed that at 10mA cm -2The catalyst can maintain stable HER operation for 1000 h at the current density, indicating that the Fe2O3@CoP@CMOH / NF-A catalyst after in-situ electrochemical activation exhibits excellent HER activity.
[0038] like Figure 6 As shown, the turnover frequencies of the prepared CoP@CMOH / NF, CoP@CMOH / NF-A, Fe2O3@CoP@CMOH / NF, and Fe2O3@CoP@CMOH / NF-A catalysts are 0.04 s. -1 0.07s -1 0.05s -1 0.09s -1 This indicates that the improved HER performance of the activated catalyst mainly stems from the enhanced intrinsic activity of the catalytic sites.
[0039] like Figure 7 As shown, the catalysts CMOH / NF, CoP@CMOH / NF, and Fe2O3@CoP@CMOH / NF have a catalyst strength of 10 mA cm⁻. 2 The overpotentials of the OER at the given current densities were 252 mV, 270 mV, and 180 mV, respectively, and the Tafel slopes were 62.78 mV dec. -1 41.24mVdec -1 32.95mV dec -1 , Figure 8 The constant current test results showed that at 10mA cm -2 The catalyst can maintain stable OER operation for 1000 h at the current density, indicating that the Fe2O3@CoP@CMOH / NF catalyst exhibits excellent OER activity.
[0040] like Figure 9 As shown, a two-electrode system was constructed in 1M KOH electrolyte using Fe2O3@CoP@CMOH / NF catalyst as both cathode and anode for overall water splitting performance testing. The system was tested at 10 mA cm⁻¹. -2 At current density, only 1.44V is required to drive the reaction, and it can operate stably for 350 hours, demonstrating excellent water-splitting performance.
[0041] In summary, the ratio of cobalt to molybdenum sources and the hydrothermal temperature mainly affect the crystallinity and morphology of the cobalt-molybdate hydrate precursor. Increased crystallinity leads to an increase in columnar diameter and a decrease in catalytic performance. The phosphating temperature primarily affects the formation of the CoP active layer; temperatures below 350℃ result in insufficient phosphating and decreased catalytic performance. The ALD deposition temperature and Fe2O3 cycle number mainly affect the deposition uniformity and loading of the Fe2O3 layer; deposition temperatures above 180℃ increase the nucleation and growth rate of Fe2O3, leading to increased loading, excessive CoP coverage, and reduced catalytic performance. The in-situ electrochemical activation time affects the degree of catalyst surface structure reconstruction and the formation of active sites. Therefore, considering the synergistic optimization of all conditions, the catalyst prepared under the conditions in Example 1 is the optimal choice and exhibits the best performance.
[0042] The cobalt-based oxide composite catalyst preparation method provided in this invention is simple and low-cost. After in-situ electrochemical activation, the obtained Fe2O3@CoP@CMOH / NF catalyst exhibits significantly improved HER reaction kinetics and enhanced intrinsic activity of the catalytic sites. Simultaneously, this catalyst also demonstrates excellent performance in the OER process, thus achieving highly efficient bifunctional water electrolysis. Overall water splitting can be achieved at relatively low voltage and remains stable during long-term operation, showing promising application prospects.
[0043] The above embodiments are merely preferred embodiments of the present invention and do not constitute a limitation thereof. All equivalent variations or improvements made by those skilled in the art within the spirit and principles of the present invention should be covered within the protection scope of the present invention.
Claims
1. A method for preparing a water electrolysis catalyst, characterized in that, Includes the following steps: Preparation of cobalt-based precursors on conductive substrates; The cobalt-based precursor is subjected to phosphating treatment to form a phosphide layer as an activation induction layer; In-situ electrochemical activation was performed to obtain a water electrolysis catalyst.
2. The method for preparing the water electrolysis catalyst according to claim 1, characterized in that, The preparation of a cobalt-based precursor on a conductive substrate includes the following steps: dissolving a cobalt source and a molybdenum source in a solvent at a molar ratio of 1-2:1 to form a reaction solution; immersing the conductive substrate in the reaction solution and performing a hydrothermal reaction at 180-200°C for 5-8 hours to grow the cobalt-based precursor on the surface of the conductive substrate.
3. The method for preparing the water electrolysis catalyst according to claim 2, characterized in that, The cobalt source is cobalt nitrate hexahydrate, and the molybdenum source is sodium phosphomolybdate.
4. The method for preparing the water electrolysis catalyst according to claim 1, characterized in that, The phosphating treatment includes the following steps: placing hypophosphite as a phosphorus source upstream of the reaction vessel, placing the cobalt-based precursor downstream, and performing phosphating under inert gas protection at a temperature of 300-350°C for 1-2 hours to form a phosphide layer on the surface of the cobalt-based precursor.
5. The method for preparing the water electrolysis catalyst according to claim 1, characterized in that, Before activation treatment, an iron oxide layer is deposited on the surface of the phosphide layer as a synergistic reinforcement layer.
6. The method for preparing the water electrolysis catalyst according to claim 5, characterized in that, Iron oxide layers were deposited using atomic layer deposition (ALD) technology with ozone-assisted ALD. The precursor was ferrocene, the source temperature was 100℃, the deposition temperature was 180-200℃, and the number of deposition cycles was 50-200.
7. The method for preparing the water electrolysis catalyst according to claim 1, characterized in that, The in-situ electrochemical activation treatment includes the following steps: electrochemically treating the structure after depositing the iron oxide layer in a constant current mode to obtain the activated water electrolysis catalyst; wherein the current density is 10 mA cm⁻¹. -2 The activation time is 2-5 hours.
8. A water electrolysis catalyst, characterized in that, It is prepared by the method described in any one of claims 1-7; the water electrolysis catalyst has a multi-level heterogeneous structure.
9. The water electrolysis catalyst according to claim 8, characterized in that, The water electrolysis catalyst is a cobalt-based oxide synergistically regulated by CoP / Fe2O3, with a nanosheet-like morphology on its surface.
10. The application of the water electrolysis catalyst according to any one of claims 8-9, characterized in that, The application of the water electrolysis catalyst in water electrolysis.