Preparation method and application of cobalt phosphide electrocatalyst with adjustable interface water hydrogen bond network

Abstract

This invention discloses a method for preparing a cobalt phosphide electrocatalyst with a tunable interfacial water hydrogen bond network and its application, belonging to the field of electrocatalytic materials. The invention uses cobalt nitrate, variable-valence metal chloride salts, and urea as raw materials to synthesize a hydroxide precursor, which is then subjected to a simple low-temperature phosphating reaction followed by in-situ oxidation and reconstruction during the oxygen evolution reaction of water electrolysis. The preparation method of this invention has advantages such as simple operation, high efficiency, environmental friendliness, strong controllability, and low cost. The prepared cobalt phosphide oxygen evolution electrocatalyst possesses advantages such as a tunable interfacial water hydrogen bond network, high stability, and excellent oxygen evolution activity.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials, specifically relating to a method for preparing a cobalt phosphide electrocatalyst with a tunable interfacial water-hydrogen bond network and its application. Background Technology

[0002] With traditional fossil resources dwindling while energy demand continues to rise, the combined effect is creating increasingly severe pressure on the ecological environment. Accelerating the construction of a clean, low-carbon, safe, and efficient new energy system has become a global consensus. Developing efficient energy conversion technologies urgently requires overcoming the technical challenges at the level of the reaction principles behind key materials, and innovating material design and preparation methods.

[0003] Hydrogen production through water electrolysis is a green and efficient energy conversion method that has attracted much attention due to its advantages such as high product purity, wide availability of raw materials, and zero carbon emissions. In the water electrolysis process, the oxygen evolution reaction (OER) involves a four-electron transfer process with slow kinetics, making it crucial to the overall energy conversion efficiency. Therefore, developing efficient, stable, and low-cost oxygen evolution electrocatalysts is of great significance for promoting the development of hydrogen production technology through water electrolysis.

[0004] Among non-precious metal oxygen evolution catalysts, cobalt-based materials have become a research hotspot due to their excellent oxygen evolution activity, structural tunability, and abundant resources. In recent years, cobalt phosphide (CoP) has been widely used as an oxygen evolution electrocatalyst due to its superior conductivity and catalytic stability. Studies have shown that the surface and interfacial microenvironment of the catalyst, especially the hydrogen bond network structure of interfacial water molecules, has a significant impact on the adsorption behavior of intermediates and the reaction pathway in the oxygen evolution reaction. By modulating the interfacial water hydrogen bond network, the interaction between reactants and active sites can be optimized, thereby improving catalytic efficiency.

[0005] However, a simple and controllable preparation strategy for regulating interfacial water hydrogen bond networks is still lacking. Existing methods mostly rely on complex surface modifications or harsh synthesis conditions, making it difficult to achieve precise design and reproducible construction of hydrogen bond network structures. Therefore, developing a cobalt phosphide electrocatalyst capable of effectively regulating interfacial water hydrogen bond networks has significant theoretical value and application prospects. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing a method for preparing a cobalt phosphide electrocatalyst with a tunable interfacial water hydrogen bond network and its application. The cobalt phosphide oxygen evolution electrocatalyst prepared by this invention possesses characteristics such as tunable interfacial water hydrogen bond network, high stability, and excellent oxygen evolution activity.

[0007] The present invention discloses a method for preparing a cobalt phosphide electrocatalyst with tunable interfacial water-hydrogen bond network, comprising the following steps:

[0008] Step 1: Add cobalt nitrate, first variable valence metal chloride, ammonium fluoride and urea to a container containing solvent and mix well. Stir thoroughly until completely dissolved to obtain a mixed reaction solution.

[0009] Step 2: The mixed reaction solution is subjected to hydrothermal reaction at 100-160 °C for 8 hours. The resulting product is washed and dried to obtain the cobalt hydroxide precursor.

[0010] Step 3: Disperse the obtained cobalt hydroxide precursor in a solution of a second variable valence metal chloride and react for 10-120 minutes to obtain a dual variable valence metal-doped cobalt hydroxide precursor;

[0011] Step 4: The obtained dual-valence metal-doped cobalt hydroxide precursor was phosphated with sodium hypophosphite at 300-400 °C for 2 hours, and after cooling, cobalt phosphide electrocatalyst was obtained.

[0012] Step 5: Place the cobalt phosphide electrocatalyst in a potassium hydroxide solution and perform oxidative reconstruction at different voltages to obtain a cobalt phosphide electrocatalyst with tunable interfacial water-hydrogen bond network.

[0013] in:

[0014] In step 1, the molar ratio of the first variable valence metal chloride salt to cobalt nitrate, ammonium fluoride and urea is 0.05~0.2:1:2.5:5.

[0015] In step 3, the mass ratio of the second variable-valence metal chloride salt to the cobalt hydroxide precursor is 0.1 to 1:1.

[0016] The first and second variable-valence metal chloride salts are selected from ferric chloride, cerium chloride, chromium chloride, vanadium chloride, tin chloride, or aluminum chloride, and the first and second variable-valence metal chloride salts are different. The first variable-valence metal salt functions to regulate structure by introducing a metal element that readily undergoes partial ion leaching, which, in conjunction with the second variable-valence metal salt, promotes electrochemical oxidation and reconstruction. The second variable-valence metal salt functions to enhance activity by introducing metal ions that are oxygen-loving intermediates, used to regulate the hydrogen bond coordination number of water at different interfaces, thereby optimizing the hydrogen bond network of the water at the interface.

[0017] The solvent used in the preparation process is deionized water or ethanol.

[0018] In step 4, the mass ratio of the dual-variable-valence metal-doped cobalt hydroxide precursor to sodium hypophosphite is 1:20.

[0019] In step 5, the oxidative reconstruction is carried out in a 1.0 mol / L potassium hydroxide solution at a voltage of 1.0-1.8 V, and the water-hydrogen bond network at the interface of the cobalt phosphide electrocatalyst is effectively controlled through the electrochemical oxidative reconstruction process.

[0020] The present invention relates to the application of cobalt phosphide electrocatalyst in the oxygen evolution reaction of water electrolysis.

[0021] The specific reaction conditions were as follows: using the prepared catalyst as the anode, a platinum sheet as the cathode, and an Hg / HgO reference electrode to form a three-electrode system; 25 ℃; 1.0 M KOH electrolyte; and a test voltage range of 0.8 ~ 1.8 V. RHE The sweep speed is 5 mV / s.

[0022] The beneficial effects of this invention are reflected in:

[0023] 1. This invention achieves regulation of the hydrogen bond network of water molecules at the catalyst surface through precursor structure design and electrochemical oxidation reconstruction strategy, which significantly improves the oxygen evolution reaction activity.

[0024] 2. The preparation method of the present invention is simple to operate, does not require high-temperature calcination, has low energy consumption, and is under mild conditions, avoiding catalyst agglomeration. The prepared catalyst has good dispersibility and controllable structure, making it suitable for large-scale preparation.

[0025] 3. The raw materials used in this invention are all non-precious metal salts, which are abundant and inexpensive. The solvents are mainly water or ethanol, which are environmentally friendly.

[0026] 4. The prepared cobalt phosphide oxygen evolution electrocatalyst exhibits excellent oxygen evolution catalytic activity and good stability, achieving 500 mA cm⁻¹. -2 The required overpotential for the current density is lower than the current industrial requirement of 300 mV. Attached Figure Description

[0027] Figure 1 The image shown is a scanning electron microscope image of the cobalt phosphide electrocatalyst obtained in Example 1, which shows that it has a uniform nanosheet axial growth structure.

[0028] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the cobalt phosphide electrocatalyst obtained in Example 1. From... Figure 2 As can be seen, doping with dual-valence metal elements does not change the crystal structure of cobalt phosphide, and the main cobalt phosphide diffraction peaks at 31.5° and 36.4° are obvious.

[0029] Figure 3Figure a shows the interfacial water ratio for different hydrogen bond coordination numbers of the cobalt phosphide electrocatalyst obtained in Example 1, where OCP represents the open-circuit voltage. Figure a shows that the interfacial water hydrogen bond network of the cobalt phosphide electrocatalyst without the introduction of a variable-valence metal element has a low content of free water; the introduction of the first variable-valence metal element has a small effect on increasing the content of free water with low coordination hydrogen bonds; the introduction of the second variable-valence metal element significantly increases the content of free water with low coordination hydrogen bonds, indicating a significant improvement in the rigidity of the interfacial water hydrogen bond network. Figure b shows the catalytic performance of the cobalt phosphide electrocatalyst obtained in Example 1. Figure b shows that after controlling the interfacial water hydrogen bond network with dual variable-valence metal element doping, the overpotential required to achieve a specific current density is significantly lower than that of undoped or single variable-valence metal element doping, driving 500 mA cm⁻¹. -2 The current density requires only an overpotential of 284 mV.

[0030] Figure 4 The image shown is a scanning electron microscope image of the cobalt phosphide electrocatalyst obtained in Example 2, which shows that it has a uniform nanosheet axial growth structure.

[0031] Figure 5 Figure a shows the interfacial water proportion for different hydrogen bond coordination numbers of the catalyst obtained in Example 2, where OCP represents the open-circuit voltage. As can be seen from Figure a, compared to the undoped catalyst in Example 1, it significantly increases the proportion of free water with low coordination hydrogen bond numbers to 9-12%, achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the catalyst obtained in Example 2, indicating its driving voltage at 500 mA cm⁻¹. -2 The current density requires only an overpotential of 292 mV.

[0032] Figure 6 The image shown is a scanning electron microscope image of the catalyst obtained in Example 3, showing that it has a uniform nanosheet axial growth structure.

[0033] Figure 7 Figure a shows the interfacial water proportion for different hydrogen bond coordination numbers of the catalyst obtained in Example 3, where OCP represents the open-circuit voltage. Compared to the undoped catalyst in Example 1, it significantly increased the proportion of free water with low coordination hydrogen bond numbers to 10-14%, achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the catalyst obtained in Example 3, indicating its driving voltage at 500 mA cm⁻¹. -2 The current density requires only an overpotential of 276 mV.

[0034] Figure 8 The image shown is a scanning electron microscope image of the catalyst obtained in Example 4, which shows that it has a uniform nanosheet axial growth structure.

[0035] Figure 9Figure a shows the interfacial water proportion for different hydrogen bond coordination numbers of the catalyst obtained in Example 4, where OCP represents the open-circuit voltage. Compared to the undoped catalyst in Example 1, it significantly increased the proportion of free water with low coordination hydrogen bond numbers to 10-13%, achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the catalyst obtained in Example 4, indicating its driving voltage at 500 mA cm⁻¹. -2 The current density requires only an overpotential of 288 mV. Detailed Implementation

[0036] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The following embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following embodiments.

[0037] All reagents used were commercially available analytical grade.

[0038] Example 1:

[0039] (1) Cobalt nitrate, chromium chloride, ammonium fluoride and urea are added to deionized water in a ratio of 1:0.05:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution.

[0040] (2) The mixed reaction solution was transferred to a polytetrafluoroethylene reactor and hydrothermally reacted at 120 °C for 8 hours. The product was washed and dried to obtain the cobalt hydroxide precursor.

[0041] (3) The obtained cobalt hydroxide precursor was dispersed in ferric chloride solution with a mass ratio of ferric chloride to precursor of 0.5:1. The reaction was carried out for 60 minutes to obtain a cobalt hydroxide precursor doped with a dual variable valence metal.

[0042] (4) The obtained precursor and sodium hypophosphite were phosphated at 350 °C for 2 hours at a mass ratio of 1:20. After cooling, cobalt phosphide oxygen evolution electrocatalyst was obtained.

[0043] (5) The obtained cobalt phosphide oxygen evolution electrocatalyst was placed in a potassium hydroxide solution of 1.0 mol / L and oxidatively reconstructed by scanning 10 times at a voltage of 1.0-1.6V to obtain a cobalt phosphide oxygen evolution electrocatalyst with tunable interfacial water hydrogen bond network.

[0044] In contrast:

[0045] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (3) and (4) were repeated to prepare a single variable valence metal element doped catalyst Fe-CoP.

[0046] Cobalt nitrate, chromium chloride, ammonium fluoride and urea were added to deionized water in a ratio of 1:0.05:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2) and (4) were repeated to prepare a single variable valence metal element doped catalyst Cr-CoP.

[0047] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (4) and (5) were repeated to prepare an undoped catalyst CoP.

[0048] Figure 1 The image shows a scanning electron microscope image of the obtained Fe,Cr-CoP catalyst, revealing that it has a uniform nanostructure.

[0049] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the cobalt phosphide electrocatalyst obtained in Example 1. From... Figure 2 As can be seen, doping with dual-valence metal elements does not change the crystal structure of cobalt phosphide, and the cobalt phosphide diffraction peaks at 31.5° and 36.4° are obvious.

[0050] Figure 3 Figure a shows the interfacial water proportion for different hydrogen bond coordination numbers of the obtained catalyst, indicating that it significantly increased the proportion of free water with low coordination hydrogen bond numbers to 10-13%, achieving control over the water-hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the obtained catalyst, showing its ability to drive a 500 mA cm⁻¹ current. -2 The current density requires only an overpotential of 284 mV.

[0051] The obtained catalyst was used to test the oxygen evolution reaction in water electrolysis. A three-electrode system was constructed using the prepared catalyst as the anode, a platinum sheet as the cathode, and an Hg / HgO reference electrode. The test was conducted at 25 °C with a 1.0 M KOH electrolyte, and the test voltage range was 0.8 ~ 1.8 V. RHE The scan rate was 5 mV / s. The results showed that the Fe,Cr-CoP catalyst increased the proportion of free water with low coordination hydrogen bonds to 10–13%, exhibiting excellent oxygen evolution reaction (OER) catalytic activity, achieving 500 mA cm⁻¹. -2 The current density requires only 284 mV of overpotential, which is lower than the industrial requirement of 300 mV.

[0052] Example 2:

[0053] (1) Cobalt nitrate, aluminum chloride, ammonium fluoride and urea were added to deionized water in a ratio of 1:0.05:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution.

[0054] (2) The mixed reaction solution was transferred to a polytetrafluoroethylene reactor and hydrothermally reacted at 100°C for 8 hours. The product was washed and dried to obtain the cobalt hydroxide precursor.

[0055] (3) The obtained cobalt hydroxide precursor was dispersed in ferric chloride solution with a mass ratio of ferric chloride to precursor of 0.5:1. The reaction was carried out for 120 minutes to obtain a cobalt hydroxide precursor doped with a dual variable valence metal.

[0056] (4) The obtained precursor and sodium hypophosphite were phosphated at 300 °C for 2 hours at a mass ratio of 1:20. After cooling, cobalt phosphide oxygen evolution electrocatalyst was obtained.

[0057] (5) The obtained cobalt phosphide oxygen evolution electrocatalyst was placed in a potassium hydroxide solution of 1.0 mol / L and oxidatively reconstructed by scanning 10 times at a voltage of 1.0-1.6V to obtain a cobalt phosphide oxygen evolution electrocatalyst with tunable interfacial water hydrogen bond network.

[0058] In contrast:

[0059] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (3) and (4) were repeated to prepare a single variable valence metal element doped catalyst Fe-CoP.

[0060] Cobalt nitrate, aluminum chloride, ammonium fluoride and urea were added to deionized water in a ratio of 1:0.05:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2) and (4) were repeated to prepare a single variable valence metal element doped catalyst Al-CoP.

[0061] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (4) and (5) were repeated to prepare an undoped catalyst CoP.

[0062] Figure 4 The image shows a scanning electron microscope image of the obtained Fe, Al-CoP catalyst, revealing its small nanosheet axial growth structure.

[0063] Figure 5 Figure a shows the interfacial water ratio for different hydrogen bond coordination numbers of the obtained catalyst, demonstrating a significant increase in the proportion of free water with low coordination hydrogen bond numbers to 9–12%, thus achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the obtained catalyst, indicating its ability to drive a 500 mA cm⁻¹ current. -2 The current density requires only an overpotential of 292 mV.

[0064] The obtained catalyst was used to test the oxygen evolution reaction in water electrolysis. A three-electrode system was constructed using the prepared catalyst as the anode, a platinum sheet as the cathode, and an Hg / HgO reference electrode. The test was conducted at 25 °C with a 1.0 M KOH electrolyte, and the test voltage range was 0.8 ~ 1.8 V. RHE The scan rate was 5 mV / s. The results showed that the Fe,Al-CoP catalyst increased the proportion of free water with low coordination hydrogen bond number to 9-12%, exhibiting excellent oxygen evolution reaction (OER) catalytic activity, achieving 500 mA cm⁻¹. -2 The current density requires only 292 mV of overpotential, which is lower than the industrial requirement of 300 mV.

[0065] Example 3:

[0066] (1) Add cobalt nitrate, cerium chloride, ammonium fluoride and urea to deionized water in a ratio of 1:0.1:2.5:5 and stir until completely dissolved to obtain a mixed reaction solution.

[0067] (2) The mixed reaction solution was transferred to a polytetrafluoroethylene reactor and hydrothermally reacted at 140°C for 8 hours. The product was washed and dried to obtain the cobalt hydroxide precursor.

[0068] (3) The obtained cobalt hydroxide precursor was dispersed in a vanadium chloride solution with a mass ratio of vanadium chloride to precursor of 0.2:1. The reaction was carried out for 90 minutes to obtain a cobalt hydroxide precursor doped with a dual variable valence metal.

[0069] (4) The obtained precursor and sodium hypophosphite were phosphated at 400 °C for 2 hours at a mass ratio of 1:20. After cooling, cobalt phosphide oxygen evolution electrocatalyst was obtained.

[0070] (5) The obtained cobalt phosphide oxygen evolution electrocatalyst was placed in a potassium hydroxide solution of 1.0 mol / L and oxidatively reconstructed by scanning 10 times at a voltage of 1.0-1.8V to obtain a cobalt phosphide oxygen evolution electrocatalyst with tunable interfacial water hydrogen bond network.

[0071] In contrast:

[0072] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (3) and (4) were repeated to prepare a single variable valence metal element doped catalyst V-CoP.

[0073] Cobalt nitrate, cerium chloride, ammonium fluoride and urea were added to deionized water in a ratio of 1:0.1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; Steps (2) and (4) were repeated to prepare a single variable valence metal element doped catalyst Ce-CoP.

[0074] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (4) and (5) were repeated to prepare an undoped catalyst CoP.

[0075] The obtained catalyst was tested and found to have a uniform nano-morphology and excellent oxygen evolution catalytic stability, and the interfacial water hydrogen bond network structure showed obvious tunable characteristics.

[0076] Figure 6 The image shows a scanning electron microscope image of the obtained V, Ce-CoP catalyst, revealing its uniform nanosheet axial growth structure.

[0077] Figure 7 Figure a shows the interfacial water ratio for different hydrogen bond coordination numbers of the obtained catalyst, demonstrating a significant increase in the proportion of free water with low coordination hydrogen bond numbers to 10–14%, thus achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current switching of the obtained catalyst, showing its ability to drive a 500 mA cm⁻¹ current. -2 The current density requires only an overpotential of 276 mV.

[0078] The obtained catalyst was used to test the oxygen evolution reaction in water electrolysis. A three-electrode system was constructed using the prepared catalyst as the anode, a platinum sheet as the cathode, and an Hg / HgO reference electrode. The test was conducted at 25 °C with a 1.0 M KOH electrolyte, and the test voltage range was 0.8 ~ 1.8 V. RHE The scan rate was 5 mV / s. The results showed that the V,Ce-CoP catalyst increased the proportion of free water with low coordination hydrogen bond number to 10–14%, exhibiting excellent oxygen evolution reaction (OER) catalytic activity, achieving 500 mA cm⁻¹. -2 The current density requires only 276 mV of overpotential, which is lower than the industrial requirement of 300 mV.

[0079] Example 4:

[0080] (1) Add cobalt nitrate, tin chloride, ammonium fluoride and urea to deionized water in a ratio of 1:0.1:2.5:5 and stir until completely dissolved to obtain a mixed reaction solution.

[0081] (2) The mixed reaction solution was transferred to a polytetrafluoroethylene reactor and hydrothermally reacted at 130°C for 8 hours. The product was washed and dried to obtain the cobalt hydroxide precursor.

[0082] (3) The obtained cobalt hydroxide precursor was dispersed in a vanadium chloride solution with a mass ratio of vanadium chloride to precursor of 0.2:1. The reaction was carried out for 45 minutes to obtain a cobalt hydroxide precursor doped with a dual variable valence metal.

[0083] (4) The obtained precursor and sodium hypophosphite were phosphated at 330 °C for 2 hours at a mass ratio of 1:20. After cooling, cobalt phosphide oxygen evolution electrocatalyst was obtained.

[0084] (5) The obtained cobalt phosphide oxygen evolution electrocatalyst was placed in a potassium hydroxide solution of 1.0 mol / L and oxidatively reconstructed by scanning 10 times at a voltage of 1.0-1.8V to obtain a cobalt phosphide oxygen evolution electrocatalyst with tunable interfacial water hydrogen bond network.

[0085] In contrast:

[0086] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (3) and (4) were repeated to prepare a single variable valence metal element doped catalyst V-CoP.

[0087] Cobalt nitrate, tin chloride, ammonium fluoride and urea were added to deionized water in a ratio of 1:0.1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; Steps (2) and (4) were repeated to prepare a single variable valence metal element doped catalyst Sn-CoP.

[0088] Cobalt nitrate, ammonium fluoride and urea were added to deionized water in a ratio of 1:2.5:5 and stirred until completely dissolved to obtain a mixed reaction solution; steps (2), (4) and (5) were repeated to prepare an undoped catalyst CoP.

[0089] Figure 8 The image shows a scanning electron microscope image of the obtained V, Sn-CoP catalyst, revealing its uniform nanosheet axial growth structure.

[0090] Figure 9 Figure a shows the interfacial water ratio for different hydrogen bond coordination numbers of the obtained catalyst, indicating that it significantly increased the proportion of free water with low coordination hydrogen bond numbers to 10-13%, achieving control over the hydrogen bond network structure. Figure b shows the specific voltage-current relationship of the obtained catalyst, showing its ability to drive a 500 mA cm⁻¹ current. -2 The current density requires only an overpotential of 288 mV.

[0091] The obtained catalyst was used to test the oxygen evolution reaction in water electrolysis. A three-electrode system was constructed using the prepared catalyst as the anode, a platinum sheet as the cathode, and an Hg / HgO reference electrode. The test was conducted at 25 °C with a 1.0 M KOH electrolyte, and the test voltage range was 0.8 ~ 1.8 V. RHE The scan rate was 5 mV / s. The results showed that the V,Sn-CoP catalyst increased the proportion of free water with low coordination hydrogen bond number to 10–13%, exhibiting excellent oxygen evolution reaction (OER) catalytic activity, driving a 500 mA cm⁻¹ scan. -2The current density requires only 288 mV of overpotential, which is lower than the industrial requirement of 300 mV.

[0092] In Examples 1-4, the cobalt phosphide electrocatalysts prepared by combining and doping with different dual-valence metal elements exhibited significant differences in microstructure and macroscopic catalytic performance, fully demonstrating the intrinsic relationship between structural design and performance regulation.

[0093] From a microscopic morphology perspective, although all four catalysts retained the basic axial growth structure of nanosheets, they exhibited unique morphological characteristics due to the different doping elements. Example 1, using iron and chromium co-doping, showed a clear tendency for the nanosheets to curl and cluster. This may be because the introduction of chromium caused lattice distortion, leading to bending and aggregation of the nanosheets into relatively dense clusters during growth. Example 2, using iron and aluminum as doping elements, resulted in finer nanosheets. The presence of aluminum may have limited the lateral growth of the nanosheets, resulting in a more fragmented overall structure. Example 3, introducing vanadium and cerium, showed a wider range of nanosheet size distribution, exhibiting varying sizes and reflecting the non-uniformity of the nucleation and growth process. Example 4, using vanadium and tin co-doping, resulted in tighter connections between the nanosheets, forming a more continuous network structure, which is beneficial for electron transport within the catalyst.

[0094] In terms of macroscopic performance, all four catalysts achieved effective control over the interfacial water hydrogen bond network, resulting in a significant increase in the proportion of free water with low coordination hydrogen bonds, thereby optimizing the oxygen evolution reaction kinetics. Among them, the vanadium and cerium co-doped catalyst in Example 3 showed the most outstanding performance, increasing the proportion of low coordination free water to 10%~14% and driving a 500 mA cm⁻¹ reaction. -2 The overpotential required for the current density is only 276 mV, making it the best performing of the four catalysts. The iron-chromium co-doped catalyst in Example 1, which increases the free water content to 10%–13%, has an overpotential of 284 mV, ranking second in performance. The vanadium-tin co-doped catalyst in Example 4 also achieves a free water content of 10%–13%, with an overpotential of 288 mV. The iron-aluminum co-doped catalyst in Example 2 increases the free water content to 9%–12%, with an overpotential of 292 mV, which, while slightly higher, is still better than the industrial requirement of 300 mV.

[0095] A comprehensive comparison reveals a close correlation between microstructure and catalytic performance. In Example 3, the nanosheets of varying sizes likely constructed multi-scale mass transfer channels, and combined with the synergistic advantages of vanadium and cerium in electronic structure regulation, achieving optimal hydrogen bond network regulation and oxygen evolution activity. While the coiled cluster structure of Example 1 thickened the catalyst layer to some extent, the strong electronic synergy between chromium and iron compensated for the morphological deficiencies. The continuous network structure of Example 4 facilitated electron conduction, while the fine nanosheets of Example 2, although providing a larger specific surface area, had relatively limited ability to regulate the electronic structure due to aluminum. Overall, the rational combination of dual-valence metals and the resulting differences in microstructure jointly determine the regulation efficiency of the interfacial water hydrogen bond network and the final oxygen evolution catalytic performance, validating the technical path of this invention—enhancing catalytic activity through precursor structure design and electrochemical oxidation reconstruction strategies.

[0096] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cobalt phosphide electrocatalyst with tunable interfacial water hydrogen bond network, characterized in that Includes the following steps: Step 1: Add cobalt nitrate, first variable valence metal chloride, ammonium fluoride and urea to the solvent and mix well. Stir thoroughly until completely dissolved to obtain a mixed reaction solution. Step 2: The mixed reaction solution is subjected to a hydrothermal reaction, and the resulting product is washed and dried to obtain the cobalt hydroxide precursor; Step 3: Disperse the obtained cobalt hydroxide precursor in a solution of a second variable valence metal chloride and react for 10-120 minutes to obtain a dual variable valence metal-doped cobalt hydroxide precursor; Step 4: The obtained dual-valence metal-doped cobalt hydroxide precursor was phosphated with sodium hypophosphite at 300-400 °C for 2 hours, and after cooling, cobalt phosphide electrocatalyst was obtained. Step 5: Place the cobalt phosphide electrocatalyst in a potassium hydroxide solution and perform oxidative reconstruction at different voltages to obtain a cobalt phosphide electrocatalyst with tunable interfacial water hydrogen bond network. The first variable valence metal chloride salt and the second variable valence metal chloride salt are selected from ferric chloride, cerium chloride, chromium chloride, vanadium chloride, tin chloride or aluminum chloride, and the first variable valence metal chloride salt and the second variable valence metal chloride salt are different; In step 2, the hydrothermal reaction temperature is 100-160 ℃, and the reaction time is 8 hours; In step 5, the oxidative reconstruction is carried out in a 1.0 mol / L potassium hydroxide solution at a voltage of 1.0-1.8 V.

2. The preparation method according to claim 1, characterized in that: In step 1, the molar ratio of the first variable valence metal chloride salt to cobalt nitrate, ammonium fluoride and urea is 0.05~0.2:1:2.5:

5.

3. The preparation method according to claim 1, characterized in that: In step 3, the mass ratio of the second variable-valence metal chloride salt to the cobalt hydroxide precursor is 0.1 to 1:

1.

4. The preparation method according to claim 1, characterized in that: In step 4, the mass ratio of the dual-variable-valence metal-doped cobalt hydroxide precursor to sodium hypophosphite is 1:

20.

5. A cobalt phosphide electrocatalyst with a tunable interfacial water-hydrogen bond network, prepared according to any one of claims 1-4.

6. The application of the cobalt phosphide electrocatalyst with tunable interfacial water hydrogen bond network as described in claim 5 in the oxygen evolution reaction of water electrolysis.

7. The application according to claim 6, characterized in that: A three-electrode system is formed using the cobalt phosphide electrocatalyst with tunable interfacial water-hydrogen bond network as the anode, a platinum sheet as the cathode, and Hg / HgO as the reference electrode.

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