Preparation Method and Application of Porous Carbon Film Electrode Modified with Cobalt Phosphide Nanoparticles

Abstract

The present invention provides a preparation method and application of a porous carbon film electrode modified with cobalt phosphide nanoparticles, belonging to the technical field of electrocatalysts. The preparation method of the porous carbon film electrode modified with cobalt phosphide nanoparticles is a green and scalable preparation method. First, taking low-cost biomass soybean as a natural source of carbon, nitrogen, and phosphorus, by applying the traditional method of preparing frozen tofu to transition metal phosphides (TMPs), an unprecedented "Co tofu" is prepared. After calcining the Co tofu, cobalt phosphide (Co 2 P) nanoparticles can be in-situ generated on the tofu-based carbon film to obtain a porous carbon film electrode modified with cobalt phosphide nanoparticles. Toxic reagents are not required for gas-phase phosphidation during the preparation process, and the environmental pollution is small. In addition, the porous carbon film electrode modified with cobalt phosphide nanoparticles prepared by the present invention has an overall structure and can be used as a bifunctional electrode for electrocatalytic water splitting, having excellent catalytic activities for hydrogen evolution reaction / oxygen evolution reaction (HER / OER).

Description

Technical Field

[0001] The invention belongs to the technical field of electrocatalysts, and in particular relates to a preparation method and application of a porous carbon film electrode modified with cobalt phosphide nanoparticles. Background Art

[0002] Nanostructured transition metal phosphides (TMPs) supported on porous carbon powder are considered to be a stable and efficient electrocatalyst for water splitting reactions. However, the synthesis of TMPs supported on powdered carbon usually requires the use of toxic reagents for gas phase phosphating, which produces a large amount of harmful gases such as phosphine, which is dangerous and pollutes the environment. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a method for preparing a porous carbon film electrode modified with cobalt phosphide nanoparticles, which method does not require the use of toxic reagents for gas phase phosphating and is green and environmentally friendly.

[0004] The present invention also provides an application of the porous carbon film electrode modified by the cobalt phosphide nanoparticles.

[0005] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0006] A method for preparing a porous carbon film electrode modified with cobalt phosphide nanoparticles comprises the following steps:

[0007] (1) Soybeans and deionized ultrapure water are mixed in a predetermined ratio, and then ground and filtered to obtain soy milk; the soy milk is boiled, cooled to 80-90° C., a Co salt solution is added, and mixed evenly to obtain a mixture; the mixture is allowed to stand to obtain a semisolid gel product, which is subjected to molding to obtain Co tofu;

[0008] (2) The Co tofu is freeze-dried to obtain an aerogel-like product, which is first placed in a muffle furnace for low-temperature carbonization in air, and then transferred to a tubular furnace for high-temperature carbonization in an argon atmosphere to obtain a black product. The black product is polished, ultrasonically cleaned, and vacuum dried to obtain a porous carbon film electrode modified with cobalt phosphide nanoparticles.

[0009] Preferably, in step (1), the mass ratio of soybeans to deionized ultrapure water is 1:9.

[0010] Preferably, in step (1), the mixture contains Co(NO 3 ) 2 The concentration is 0.1M.

[0011] Preferably, in step (1), the mixture is allowed to stand for 20-30 minutes.

[0012] Preferably, in step (1), the molding process is specifically: pouring the semi-solid gel product into a mold and pressing for 8-14 hours to remove excess water.

[0013] Preferably, in step (2), the freeze-drying time is 24-36 hours.

[0014] Preferably, in step (2), the low-temperature carbonization temperature is 260-300°C for 5-6 hours, the high-temperature carbonization temperature is 800-1000°C for 2-6 hours, the gas flow rate of both carbonizations is 40 mL / min, and the heating rate is 5°C / min.

[0015] Preferably, in the step (2), the carbonized product is polished using 2000-mesh sandpaper to a thickness of 400 μm.

[0016] The invention discloses an application of a porous carbon film electrode modified with cobalt phosphide nanoparticles prepared by the preparation method as a dual-functional electrode for electrocatalytic water decomposition.

[0017] It can be seen from the above technical scheme that the present invention provides a preparation method of a porous carbon film electrode modified with cobalt phosphide nanoparticles and its application, and its beneficial effects are: the preparation method of the porous carbon film electrode modified with cobalt phosphide nanoparticles described in the present invention is a green and scalable preparation method. First, low-cost soybeans are used as natural carbon, nitrogen and phosphorus sources, and the traditional frozen tofu preparation method is applied to transition metal phosphides (TMPs) to prepare unprecedented Co tofu. After calcining the Co tofu, cobalt phosphide (Co phosphide) can be in situ generated on the tofu-based carbon film (CTF). 2 P) nanoparticles to obtain the porous carbon film electrode modified with the cobalt phosphide nanoparticles; during the calcination process, Co forms Co 2 P is successfully phosphorylated, Co 2 P nanoparticles were deposited on the tofu-based carbon film in the form of being wrapped in egg yolk shells. 2 P nanoparticles can serve as reactive sites to embed Co on CTF. 2 P nanoparticles increase the electrochemically active surface area. 2 The synergistic effect between P nanoparticles and CTF exposes a large number of reactive sites, making the prepared catalyst material have excellent electrochemical performance and stability. The above method is different from the existing method of synthesizing nitrogen / phosphorus-doped carbon catalysts. It does not require the use of toxic reagents for gas phase phosphating. Therefore, a large amount of harmful gases will not be produced during the phosphating process, and the pollution to the environment is small. This simple and effective calcination strategy based on natural soybeans provides a green and sustainable idea for the existing phosphating methods.

[0018] In addition, the porous carbon film electrode modified with cobalt phosphide nanoparticles prepared by the preparation method of the present invention has an integral structure and can be directly used as a bifunctional electrode for electrocatalytic water decomposition without the use of a binder and an additional conductive agent, and has excellent hydrogen evolution reaction / oxygen evolution reaction (HER / OER) catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 YesCo 2 Scanning electron microscope (SEM) image of P@CTF.

[0020] Figure 2 YesCo 2 Transmission electron microscopy (TEM) image of P@CTF.

[0021] Figure 3 It is CTF and Co 2 X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) results of P@CTF.

[0022] Figure 4 YesCo 2 HER activity test results of P@CTF.

[0023] Figure 5 YesCo 2 OER activity test results of P@CTF. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be emphasized that the specific embodiments described herein are only used to better illustrate the present invention, are part of the embodiments of the present invention, not all of the embodiments, and are therefore not used to limit the present invention.

[0025] The present invention provides a method for preparing a porous carbon film electrode modified with cobalt phosphide nanoparticles, comprising the following steps:

[0026] (1) Soybeans and deionized ultrapure water are mixed in a predetermined ratio, and then ground and filtered to obtain soy milk; the soy milk is boiled, cooled to 80-90° C., a Co salt solution is added, and mixed evenly to obtain a mixture; the mixture is allowed to stand to obtain a semisolid gel product, which is subjected to molding to obtain Co tofu;

[0027] In one embodiment, 50 g of soybeans were soaked in ultrapure water for 12 h, the soaked soybeans were mixed with 450 mL of deionized ultrapure water and then put into a Joyoung soymilk maker, ground, and the dregs were filtered out to obtain soymilk. 300 mL of soymilk was measured, boiled, and cooled to 85 ° C. 50 mL of Co(NO 3 )2 The solution was mixed evenly to obtain a mixture in which Co(NO 3 ) 2 The concentration was 0.1 M, and the mixture was allowed to stand for 20 min to obtain a semi-solid gel product, which was poured into a homemade mold and pressed for 12 h to remove excess water to obtain Co tofu (Co 2+ @TF). In this step, low-cost biomass soybeans are used as natural sources of carbon, nitrogen and phosphorus. Co tofu is prepared by applying the traditional frozen tofu preparation method to transition metal phosphides (TMPs). When the soy milk is cooled to 85°C, Co(NO 3 ) 2 The purpose of the solution is to flocculate the protein at this temperature, thereby ensuring that Co 2 + Completely integrated into the tofu base.

[0028] (2) The Co tofu is freeze-dried to obtain an aerogel-like product, which is first placed in a muffle furnace for low-temperature carbonization in air, and then transferred to a tubular furnace for high-temperature carbonization in an argon atmosphere to obtain a black product. The black product is polished, ultrasonically cleaned, and vacuum dried to obtain a porous carbon film electrode modified with cobalt phosphide nanoparticles.

[0029] In a specific embodiment, the prepared Co tofu is freeze-dried for 24 h to obtain an aerogel-like product, which is placed in a muffle air at 260°C for low-temperature carbonization for 6 h, and then transferred to a tube furnace at 1000°C for high-temperature carbonization in an argon atmosphere for 6 h. The gas flow rate of the two carbonizations is 40 mL / min, and the heating rate is 5°C / min. A black product is obtained. The black product is carefully polished with 2000 mesh sandpaper to a thickness of 400 μm, and is cleaned with ultrasound to remove residual carbon. Finally, it is dried in a vacuum oven at 60°C for 12 h to obtain a porous carbon film decorated with cobalt phosphide nanoparticles (Co 2 P@CTF). In this step, Co 2 P@CTF material has good graphitization degree, Co 2 The hierarchical porous structure in the P@CTF structure provides a transmission channel for electrons to promote electron transfer, which is beneficial to improve the conductivity of the material and thus improve its electrochemical performance. 2 P is successfully phosphorylated, Co 2 P nanoparticles were deposited on tofu-based carbon film (CTF) in the form of yolk shells, which increased the electrochemically active surface area. 2 The synergistic effect between P nanoparticles and CTF exposes a large number of reactive sites to improve the electrochemical reaction activity and stability.

[0030] Please see Figure 1 , Co 2 The morphology of P@CTF, Figure 1 (a) is Co 2 Photo of P@CTF, (b) Co 2 SEM image of the overall view of P@CTF, (c) Co 2 Top view SEM image of P@CTF, (d) Co 2 Side view SEM image of P@CTF, (e) Co 2 P@CTF 2 P nanoparticle distribution, (f) Co 2 Electrolyte wettability of P@CTF, (g) Co 2 SEM images of P@CTF and corresponding elemental maps (C, N, Co, P), (h) CTF and Co 2 The conductivity of the P@CTF electrode. Figure 1 As shown in (a), the Co obtained after carbonization 2 P@CTF is an integrated structure. Figure 1 (b)-(d) show the Co 2 P@CTF has an interconnected isotropic pore structure, and Co 2 The surface of P@CTF is rich in pores, with sizes ranging from 5 to 50 μm, and the pore sizes in the vertical direction are the same. Figure 1 (e) A large number of nanoparticles can be observed deposited on CTF, Co 2 P nanoparticles exist in the form of yolk shells. Due to the presence of hierarchical porous structure and sufficient channels, the electrolyte droplets are 2 P@CTF can be quickly absorbed. Figure 1 (f) shows that the electrolyte wettability is good, which ensures that the electrolyte can be quickly transported to the three-phase reaction site, thereby improving the hydrogen evolution reaction / oxygen evolution reaction (HER / OER) performance. Figure 1 In the energy dispersive X-ray (EDX) elemental map of (g), it can be clearly observed that the four elements C, N, P, and Co are evenly distributed on the tofu-based carbon matrix. Figure 1 (h) shows that CTF is at 2.56S·m -1 It exhibits excellent conductivity and contains Co 2 CoP nanoparticles 2 The conductivity of the P@CTF electrode is 5.01 S·m -1 , has better conductivity than CTF.

[0031] See also Figure 2 , using transmission electron microscopy (TEM) to analyze the Co 2The microstructure of P@CTF was characterized. Figure 2 (a) is Co 2 Low-resolution TEM image of P@CTF, (b) Co 2 Low-resolution image of P@CTF, the inserted image is the particle size distribution result, (c) is the HRTEM image, and (d) is the Co 2 HAADF-STEM image of P@CTF and the corresponding elemental maps of C, N, Co, and P. Figure 2 (a)-(b) show that after high temperature calcination, Co with a diameter of 5-35 nm was in situ grown on CTF. 2 P nanoparticles. Figure 2 (c) further reveals that the coated Co 2 P nanoparticles, whose interplanar spacings are 0.35 nm and 0.20 nm, corresponding to Co 2 The (111) surface of P and the (002) surface of graphite carbon, Co 2 The P nanoparticles are wrapped by a thin layer of graphitic carbon of about 1.5 nm, with an interlayer spacing of about 0.35 nm. Figure 2 (d) Elemental mapping and transmission electron microscopy (TEM) further confirmed that the Co and P elements in the prepared nanoparticles were uniformly distributed in the CTF. EDX showed that the four elements C, N, Co, and P were evenly distributed, and the Co and P elements were almost overlapping.

[0032] See also Figure 3 , X-ray diffraction (XRD) revealed that CTF and Co 2 Chemical structure of P@CTF, Figure 3 (a) is the XRD spectrum, (b) is the Raman spectrum, (c) is the XPS measurement spectrum, and (d) is the CTF and Co 2 XPS spectra of N 1s of P@CTF, (e) of CTF and Co 2 XPS spectrum of P 2p of P@CTF, (f) is Co 2 XPS spectrum of Co 2p of P@CTF. Figure 3 (a) shows the prepared CTF and Co 2 The main indicator of P@CTF, the XRD spectrum of CTF shows that when 2θ is 24.0° and 44.0°, corresponding to the (002) plane and (100) plane of graphite carbon, there are two strong diffraction peaks, indicating that CTF has a good degree of graphitization. The two strongest peaks at 40.67° and 43.34° are mainly from Co 2 P metal nanoparticles (PDF#32-0316), which is consistent with the TEM analysis results.

[0033] Raman spectroscopy was used to further investigate the Co2 Structural features of P@CTF. Figure 3 (b) It can be seen that CTF and Co 2 P@CTF electrode at 1343cm -1 and 1586cm -1 There are two characteristic peaks at each location, representing disordered carbon (D band) and graphite carbon (G band). The ID / IG value of CTF is 1.04, which is close to Co 2 P@CTF (1.02), indicating that the introduction of element Co has no significant effect on the degree of graphitization of carbon-based materials. 2 P@CTF has a good degree of graphitization, which is beneficial to improving the conductivity of the material, thereby promoting electron transfer and further improving the electrochemical performance.

[0034] X-ray photoelectron spectroscopy (XPS) was used to characterize the CTF and Co 2 The surface chemical state of P@CTF was characterized. Figure 3 (c) shows that C, N, O, Co, and P elements can be found in the prepared samples. The XPS measurement spectrum and content of the elements indicate that CTF is mainly composed of C (86.55 at.%), N (2.54 at.%), O (9.82 at.%), and P (0.28 at.%) elements. The presence of P element proves that biomass carbon materials have the basis for self-phosphorization. Figure 3 (d) is Co 2 High-resolution Co 2p XPS spectrum of P@CTF, Co 2p appearing at 777.9 eV and 793.1 eV 3 / 2 and Co 2p 1 / 2 peak, confirming that Co 2 The Co in P@CTF exists in the form of Co-P combination, which is consistent with Figure 3 (e) confirms the results, proving that Co 2 The existence of P. Figure 3 In the XPS profile of P 2p in (e), the anti-curling peaks at 129 eV and 130 eV indicate that Co 2 P was successfully phosphorylated, while the peaks at 133 eV and 132 eV represented PO binding and PO incorporation, respectively. Figure 3 (f) shows Co 2 N 1s spectrum of P@CTF. The N 1s peak fitting shows that CTF and Co 2 The N element in P@CTF exists mainly in the form of pyridinic-N, pyrrolic-N, graphitic N and oxidized N. Compared with CTF samples, Co 2The graphite nitrogen content of the P@CTF sample is significantly higher than that of the CTF sample, indicating that more N elements are embedded in the carbon shell. The synergistic effect of N elements and carbon shell further improves the electrochemical performance and long-term stability of the electrode material.

[0035] See also Figure 4 The prepared Co 2 HER activity of P@CTF catalyst and comparative example CTF and Pt / C catalysts. Figure 4 (a) is CTF, Co 2 The scan rate of P@CTF and Pt / C electrodes in 1.0 M KOH solution was 0.5 mV·s -1 HER polarization curves at , (b) CTF, Co 2 Tafel diagrams of P@CTF and Pt / C electrodes, (c) CTF, Co 2 EIS Nyquist (electrochemical impedance spectroscopy Nyquist) diagrams of P@CTF and Pt / C, (d) CTF and Co 2 Double layer capacitance of P@CTF electrode. (e) Comparison of different electrodes up to 10 mA cm -2 and 100mA·cm -2 The required overpotential, (f) is the Co 2 Long-term stability test of P@CTF electrode. Figure 4 (a) It can be clearly seen that at a current density of 10 mA cm -2 When , the HER activity of CTF electrode is the worst, with an overpotential of 136 mV. Under the same reaction conditions, Co 2 The HER activity of P@CTF was enhanced at a current density of 10 mA cm -2 The overpotential is only 66 mV at a current density of 100 mA cm -2 The overpotential is 133 mV, indicating that the Co embedded in the CTF 2 P nanoparticles are the more active HER components. Figure 4 (b) is the Tafel diagram of different electrodes. In the Tafel diagram, the smaller the Tafel slope value, the faster the current density increases, indicating that the catalyst has faster kinetics and better catalytic activity. The Tafel slope of Pt / C is 80mV·dec -1 The Tafel slope of CTF is 161mV·dec -1 ,Co 2 The Tafel slope of P@CTF is 66mV·dec -1 , and the Tafel slope of the Heyrovsky reaction (≈40 mV dec -1) is very close. 2 The HER activity of the CTF electrode with P nanoparticles is significantly lower than that of Co 2 P@CTF electrode, indicating that Co 2 P nanoparticles are Co 2 Active sites with higher HER activity in P@CTF electrode. Figure 4 (c) It can be seen that Co 2 The resistance of P@CTF electrode and CTF electrode is lower than that of Pt / C electrode. 2 CoP nanoparticles 2 The transfer resistance of the P@CTF electrode is lower, indicating that the self-supporting electrode is more conducive to electron transfer. The high conductivity and large specific surface area of ​​CTF play a favorable role in HER. Figure 4 In (d), by comparing CTF and Co 2 The double layer capacitance (C dl ), and their electrochemically active surface areas (ECSAs) were compared. CTF and Co 2 P@CTF C dl 0.25mF·cm -2 and 1.72mF·cm -2 , confirming the embedding of Co in the CTF matrix 2 P nanoparticles increase the electrochemically active surface area. In addition, the metallic Co embedded in the CTF matrix 2 The P nanoparticles are highly dispersed and work synergistically with the CTF matrix to expose a large number of active sites in HER. Figure 4 (e) shows that Co 2 The performance of the P@CTF electrode is one of the best among the recently developed Co-based electrocatalysts and other non-precious metal alkaline media HER catalysts. 2 The HER activity of P@CTF electrode is still much lower than that of Pt / C. -2 When the overpotential is as low as 9mV, at 100mA·cm -2 The Co 2 The long-term HER stability of P@CTF electrode at high current density is shown in Figure 2. Figure 4 (f) During the 100 h electrocatalytic HER process, the current density is relatively stable. At an overpotential of -1.3 V vs. RHE, the current density is 1000 mA cm -2 The overpotential of electrocatalytic HER is relatively stable at -0.197 V vs. RHE for more than 150 h, and the current density is 100 mA cm-2 It is basically unchanged. 2 P@CTF has excellent stability due to its highly active Co 2 The result of the synergistic effect of P nanoparticles and carbon shell structure.

[0036] See also Figure 5 The prepared Co2P@CTF catalyst was compared with the comparative examples CTF and RuO using a standard three-electrode configuration in 1.0 M KOH electrolyte. 2 OER activity of the electrode. Figure 5 (a) is CTF, Co 2 P@CTF、RuO 2 OER polarization curve of the electrode, (b) CTF of OER, Co 2 P@CTF、RuO 2 Tafel diagram of the electrode, (c) CTF, Co 2 P@CTF、RuO 2 EIS Nyquist (electrochemical impedance spectroscopy Nyquist) diagram, (d) CTF and Co 2 Double layer capacitance of P@CTF electrode. (e) Comparison of different electrodes up to 10 mA cm -2 and 100mA·cm -2 The required overpotential, (f) is the Co 2 Long-term stability test of P@CTF electrode. Figure 5 (a) It can be seen that it does not contain Co 2 The CTF electrode of P nanoparticles has almost no OER performance, and the Co-loaded 2 CoP nanoparticles 2 P@CTF electrode has excellent OER activity. Figure 5 (b) Co 2 The Tafel slope of the P@CTF electrode is 93 mV·dec -1 , with RuO 2 The Tafel slope (129mV·dec -1 ), indicating that the first electron transfer process is RDS. This unusually high OER activity is attributed to Co 2 The unique structure of P@CTF electrode, in which Co is directly embedded on the CTF substrate 2 P can serve as an efficient active site and charge separation site for OER, while the internal metal Co 2 The P core can quickly transfer electrons to the CTF matrix, thus making Co 2 The P@CTF electrode has excellent electrocatalytic OER performance. Figure 5EIS analysis of (c) shows that compared with the CTF electrode, Co 2 The smaller semicircle in the Nyquist plot of the P@CTF electrode confirms the reduction of its charge transfer resistance, which indicates that the Co loading 2 The electrode of P nanoparticles is beneficial to electron transfer and the increase of active sites. Figure 5 (d) In 2 P@CTF electrode C dl The value is 0.17mF·cm -2 , much higher than CTF (0.017mF·cm -2 ), Co 2 P@CTF C dl The value is larger than CTF, which means that Co 2 The active sites for OER in P@CTF are richer than those in CTF alone. Figure 5 Different polarization curves in a are at 100 mA·cm -2 The current density value under the current density, the change of OER catalytic activity is basically consistent with the ECSA of the electrode. Figure 5 (e) Display Co 2 The performance of P@CTF electrode is better than that of the commercial catalyst RuO 2 As with most other Co-based catalysts, Co 2 The P@CTF electrode requires an overpotential of 230 mV and 380 mV to reach 10 mA cm -2 and 100mA·cm -2 The current density is higher than that of the commercial catalyst RuO 2 (300 and 350mV) are much lower. Figure 5 As shown in (f), at an initial current density of 100 mA cm -2 Co was tested at a constant applied potential of 1.65 V vs. RHE. 2 OER stability of P@CTF electrode, Co 2 The current density of OER on the P@CTF electrode gradually decreased with the reaction time, and the activity was still 81% after 50 h of electrolysis. -2 Co was tested at a constant applied potential of 2.2 V vs. RHE. 2 The OER stability of the P@CTF electrode, but the rapid current decay, is due to the Co 2 Oxidation of P nanoparticles.

[0037] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for preparing a porous carbon film electrode modified with cobalt phosphide nanoparticles, Features: The following steps are involved: (1) Soybeans and deionized ultrapure water are mixed in a predetermined ratio, and then ground and filtered to obtain soy milk; the soy milk is boiled, cooled to 80-90° C., a Co salt solution is added, and mixed evenly to obtain a mixture; the mixture is allowed to stand to obtain a semisolid gel product, which is subjected to molding to obtain Co tofu; (2) The Co tofu is freeze-dried to obtain an aerogel-like product, which is first placed in a muffle furnace for low-temperature carbonization in air, and then transferred to a tubular furnace for high-temperature carbonization in an argon atmosphere to obtain a black product. The black product is polished, ultrasonically cleaned, and vacuum dried to obtain a porous carbon film electrode modified with cobalt phosphide nanoparticles.

2. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles according to claim 1, Features: In the step (1), the mass ratio of soybeans to deionized ultrapure water is 1:

9.

3. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles according to claim 1, Features: In the step (1), the mixture contains Co(NO 3 ) 2 The concentration is 0.1 M.

4. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles according to claim 1, Features: In the step (1), the mixture is allowed to stand for 20-30 minutes.

5. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles according to claim 1, Features: In the step (1), the molding process specifically comprises: pouring the semi-solid gel product into a mold and pressing for 8-14 hours to remove excess water.

6. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles as claimed in claim 1, Features: In the step (2), the freeze-drying time is 24-36 h.

7. The method for preparing a porous carbon film decorated with cobalt phosphide nanoparticles according to claim 1, Features: In the step (2), the low-temperature carbonization temperature is 260-300°C for 5-6 h, the high-temperature carbonization temperature is 800-1000°C for 2-6 h, the gas flow rate of both carbonizations is 40 mL / min, and the heating rate is 5°C / min.

8. The method for preparing the porous carbon film electrode modified with cobalt phosphide nanoparticles as claimed in claim 1, Features: In the step (2), the black product is polished using 2000-grit sandpaper to a thickness of 400 μm.

9. Use of a porous carbon film electrode modified with cobalt phosphide nanoparticles prepared by the preparation method according to any one of claims 1 to 8 as a bifunctional electrode for electrocatalytic water decomposition.

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