Titanium nitride / transition metal phosphide heterojunction electrode with nano array structure, preparation method of titanium nitride / transition metal phosphide heterojunction electrode and application of titanium nitride / transition metal phosphide heterojunction electrode in seawater electrolysis for hydrogen production

Abstract

The invention belongs to the technical field of energy and electrochemical catalysis, and discloses a titanium nitride / transition metal phosphide heterojunction electrode with a nano array structure, a preparation method of the titanium nitride / transition metal phosphide heterojunction electrode and application of the titanium nitride / transition metal phosphide heterojunction electrode to seawater electrolysis for hydrogen production. The electrode comprises titanium nitride grown on a conductive substrate and transition metal phosphides (such as cobalt phosphides, nickel phosphides, iron phosphides or a combination thereof) loaded on the surface of the titanium nitride. According to the composite electrode, a titanium dioxide nano array is synthesized on a conductive substrate through seed crystal assisted solvothermal, and a titanium nitride electrode is obtained through high-temperature nitridation; and then carrying out hydrothermal loading on a transition metal precursor and carrying out low-temperature phosphating treatment to obtain the titanium nitride / transition metal phosphide composite electrode. By combining high conductivity and corrosion resistance of titanium nitride and high catalytic activity and electrochemical stability of transition metal phosphide, the technical problems that a traditional electrode is easy to corrode and poor in catalytic stability in a seawater environment are solved; the synthesized titanium nitride / transition metal phosphide composite electrode is of a multi-scale graded nano array structure, and the micro-nano composite morphology of the composite electrode can be used for inducing the turbulence effect of an electrolyte, so that hydrogen evolution bubble separation is accelerated, and interface adsorption of precipitates such as magnesium hydroxide / calcium hydroxide is inhibited. Through the innovative hierarchical heterostructure design, an efficient, low-cost and long-life electrode solution is provided for direct hydrogen production from seawater, and the method has a wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a nano-array structured titanium nitride / transition metal phosphide heterojunction electrode and a preparation method and seawater electrolysis hydrogen production application thereof, and belongs to the technical field of energy and electrochemical catalysis. BACKGROUND

[0002] With the promotion of global energy structure transformation, hydrogen energy as a clean and efficient secondary energy is attracting much attention. Water electrolysis hydrogen production technology has become an important way for green hydrogen production due to its zero carbon emission characteristics, and seawater as the most abundant water resource on earth can greatly reduce freshwater consumption when directly electrolyzed to produce hydrogen, which has significant economic and environmental benefits. However, seawater electrolysis faces challenges such as high salinity, complex ion environment, strong corrosion and competitive side reactions, which puts higher requirements on the stability, selectivity and catalytic activity of electrode materials.

[0003] Although traditional noble metal-based catalysts (such as Pt) exhibit excellent hydrogen evolution reaction (HER) activity, their high cost and scarcity limit large-scale application. Therefore, developing efficient, stable and low-cost non-noble metal catalysts has become a research focus in the field of seawater electrolysis hydrogen production. Transition metal phosphides (TMPs) and nitrides (TMNs) have great potential in seawater electrolysis due to their unique electronic structure and catalytic performance. In particular, transition metal phosphides such as FeCoP exhibit low overpotential and high electrocatalytic activity during seawater electrolysis. However, single-component catalysts still face problems such as insufficient active site exposure and low electron transmission efficiency, especially in the high-chloride ion concentration seawater environment, which is prone to structural collapse and performance degradation. Moreover, the single material structure often limits its stability and electrocatalytic efficiency under high current density.

[0004] In recent years, heterojunction engineering and micro-nano structure regulation have been proven to be effective strategies to improve catalytic performance. By constructing a heterojunction, the electronic structure of the active site can be optimized. A multi-scale hierarchical nano-array structure not only increases the active site density, but also promotes mass transfer and bubble detachment, and inhibits the interfacial adsorption of magnesium / hydroxide calcium precipitates. Therefore, developing a titanium nitride / transition metal phosphide electrode with a multi-scale hierarchical structure can effectively improve the electrocatalytic activity of the electrode, and also improve its stability and durability under high current density, thereby realizing efficient and stable seawater electrolysis hydrogen production. This breakthrough in technology will provide a more promising solution for seawater electrolysis hydrogen production and promote the sustainable use of marine energy. SUMMARY

[0005] The application relates to a nano-array structured titanium nitride / transition metal phosphide heterojunction electrode and a preparation method and seawater electrolysis hydrogen production application thereof, and belongs to the technical field of energy and electrochemical catalysis.

[0006] In order to achieve the above-mentioned purpose, the present application provides a nano-array structured titanium nitride / transition metal phosphide heterojunction electrode, wherein the transition metal phosphide is phosphide of iron, cobalt, nickel and combinations thereof, the transition metal phosphide is uniformly distributed on the surface of the titanium nitride, the electrode presents a multi-scale hierarchical nano-array structure, and excellent catalytic activity is exhibited in seawater hydrogen evolution.

[0007] The present application also provides a preparation method of the nano-array structured titanium nitride / transition metal phosphide heterojunction electrode, comprising the following steps:

[0008] Step 1: titanium source and organic solvent are fully mixed to obtain solution A, the conductive substrate is soaked in solution A and then dried, and then annealing in a muffle furnace to achieve successful loading of TiO2 seeds on the conductive substrate. Subsequently, the titanium source and the solvent are fully mixed to obtain solution B, and the above electrode is placed in solution B for hydrothermal reaction to prepare a TiO2 nano-array electrode.

[0009] Step 2: the TiO2 electrode obtained in step 1 is subjected to high-temperature nitriding treatment in an inert atmosphere to obtain a titanium nitride electrode.

[0010] Step 3: the titanium nitride electrode obtained in step 2 is immersed in a transition metal salt precursor solution, and transition metal hydroxide is loaded by hydrothermal reaction.

[0011] Step 4: the product obtained in step 3 is subjected to low-temperature phosphating treatment in an inert atmosphere to obtain a titanium nitride / transition metal phosphide composite electrode.

[0012] Preferably, in step 1:

[0013] The cutting area of the conductive substrate (carbon paper or carbon cloth) is 2 cm*3 cm, and needs to be pretreated: sequentially cleaned with acetone, ethanol and ultrapure water for 15-25 minutes, and then dried at 50-70°C;

[0014] The solution A is titanium n-butoxide isopropanol solution, and the concentration of titanium n-butoxide is 0.04-0.08 M.

[0015] The calcination temperature of the muffle furnace is 350-450°C, and the calcination time is 1-2 h.

[0016] The solution B is a mixed solution of titanium n-butoxide, hydrochloric acid and acetone, wherein the volume fraction of titanium n-butoxide is 3-8%;

[0017] The hydrothermal reaction temperature is 180-200°C, and the hydrothermal reaction time is 2-3 h.

[0018] Preferably, in step 2:

[0019] The inert gas is any one of nitrogen or argon.

[0020] The nitrogen source during the nitriding is melamine, and the used mass is 0.8-1.2g;

[0021] The nitriding treatment temperature is 700-800℃;

[0022] The nitriding time is 2-3h;

[0023] The heating rate is 3-5℃ / min;

[0024] The flow rate of the inert gas flow is 50-200mL / min.

[0025] Preferably, in step 3:

[0026] The transition metal salt precursor solution is one or two of a cobalt salt, a nickel salt and an iron salt, and an ultrapure water solution of urea and ammonium fluoride, wherein the concentration of the cobalt salt, the nickel salt and the iron salt is 0.01-0.15M, the concentration of the urea is 0.05-0.2M, and the concentration of the ammonium fluoride is 0.1-0.4M;

[0027] The hydrothermal reaction temperature is 120-150℃, and the hydrothermal reaction time is 10-16h.

[0028] Preferably, in step 4:

[0029] The inert gas is any one of nitrogen or argon;

[0030] The phosphorus source during the phosphorization is sodium hypophosphite, and the used mass is 0.5-1.0g;

[0031] The phosphorization treatment temperature is 300-350℃, the selenization time is 1-2h, and the heating rate is 2-5℃ / min;

[0032] The flow rate of the inert gas flow is 50-200mL / min.

[0033] In addition, the application further provides an application of the titanium nitride / transition metal phosphide heterojunction electrode with the above nano array structure in electrolysis of seawater to produce hydrogen.

[0034] Compared with the prior art, the application has the following beneficial effects:

[0035] 1. The application provides a preparation method of a nano-array structure titanium nitride / transition metal phosphide heterojunction electrode, which adopts a template-assisted hydrothermal method combined with a gas-phase nitridation / phosphorization process to prepare a multi-scale hierarchical nano-array structure titanium nitride / transition metal phosphide composite electrode, and the process is simple, controllable and easy for large-scale production; the raw materials are titanium nitride and transition metal (cobalt, nickel, iron, etc.) phosphide, which are non-noble metal materials with abundant reserves, thereby avoiding the dependence on scarce noble metals, significantly reducing the electrode preparation cost, and effectively inhibiting the agglomeration of the materials in the synthesis process through a step-by-step reaction, and ensuring the uniformity of the composite electrode structure.

[0036] 2. The nano-array structure titanium nitride / transition metal phosphide heterojunction electrode prepared in the application has both micro-scale channels and nano-scale active units, which not only greatly increases the specific surface area to expose more catalytically active sites, but also induces turbulent flow of the electrolyte, accelerates the separation of hydrogen bubbles, promotes the mass transfer efficiency of seawater electrolyte, and inhibits the interfacial adsorption of magnesium hydroxide, calcium and other precipitates, thereby significantly improving the catalytic activity and stability of seawater electrolysis hydrogen production.

[0037] 3. The nano-array structure titanium nitride / transition metal phosphide heterojunction electrode prepared in the application utilizes the performance synergy of the heterostructure formed by titanium nitride and transition metal phosphide, the high conductivity of titanium nitride ensures fast charge transfer, the excellent corrosion resistance resists the erosion of the complex seawater environment, and the transition metal phosphide provides efficient catalytically active centers; this synergistic effect solves the problems of insufficient conductivity, easy corrosion and fast catalytic activity decay of traditional electrodes in seawater, so that the electrode remains efficient and stable in long-term operation, has extremely strong practical application value, and is especially suitable for large-scale industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the specific embodiments or prior art description will be briefly introduced as follows.

[0039] Figure 1 The scanning electron microscope image of the iron cobalt phosphide / titanium nitride electrode prepared in Example 1 of the application;

[0040] Figure 2 The XRD spectrum of the iron cobalt phosphide / titanium nitride electrode prepared in Example 1 of the application;

[0041] Figure 3 The contact angle and bubble contact angle of the iron cobalt phosphide / titanium nitride electrode prepared in Example 1 of the application in seawater medium;

[0042] Figure 4The bubble photos of the surface of the iron cobalt phosphide / titanium nitride electrode prepared for the embodiment 1 of the present application under constant current density in seawater medium;

[0043] Figure 5 The polarization curves of the HER performance of the embodiments 1-3 and the comparative examples 1 and 2 of the present application.

[0044] Figure 6 The constant current stability test curves of the embodiments 1-3 of the present application, showing the stability thereof in long-time operation.

[0045] Figure 7 The actual photos of the surface calcium and magnesium precipitation adhesion of the embodiment 1 of the present application after the constant current test in natural seawater. DETAILED DESCRIPTION

[0046] The technical solutions of the present application are exemplarily described below through specific embodiments. It is emphasized that the embodiments are only used for illustrating the core concept of the present application, and do not constitute a limitation on the scope of the claims. In the specific implementation process, the experimental parameters not explicitly marked are all executed by using the conventional technical conditions or the standard recommended by the equipment supplier. The experimental materials and equipment involved are not specially marked by the manufacturer, and are all the standardized products known in the art and available through commercial channels.

[0047] According to the first aspect of the present application, a preparation method of a titanium nitride / transition metal phosphide heterojunction electrode with nano-array structure is provided, comprising the following steps:

[0048] Step 1: titanium source is fully mixed with an organic solvent to obtain solution A, the conductive substrate is soaked in solution A and then dried, and then annealed in a muffle furnace to achieve successful loading of TiO2 seeds on the conductive substrate. Subsequently, the titanium source is fully mixed with a solvent to obtain solution B, and the above electrode is placed in solution B for hydrothermal reaction to prepare a TiO2 nano-array electrode.

[0049] The cutting area of the conductive substrate (carbon paper or carbon cloth) is 2 cm*3 cm, and needs to be pretreated: sequentially cleaned with acetone, ethanol and ultrapure water for 15-25 minutes, and then dried at 50-70°C;

[0050] The solution A is a titanium n-butoxide isopropyl alcohol solution, and the concentration of titanium n-butoxide is 0.04-0.08 M.

[0051] The calcination temperature of the muffle furnace is 350-450°C, and the calcination time is 1-2 h.

[0052] The solution B is a mixed solution of titanium n-butoxide, hydrochloric acid and acetone, wherein the volume fraction of titanium n-butoxide is 3-8%;

[0053] The hydrothermal reaction temperature is 180-200℃, and the hydrothermal reaction time is 2-3h.

[0054] Step 2: The TiO2 electrode obtained in step 1 is subjected to high-temperature nitridation treatment in an inert atmosphere to obtain a titanium nitride electrode.

[0055] The inert gas is any one of nitrogen or argon;

[0056] The nitrogen source during the nitridation is melamine, and the mass used is 0.8-1.2g;

[0057] The nitridation treatment temperature is 700-800℃;

[0058] The nitridation time is 2-3h;

[0059] The heating rate is 3-5℃ / min;

[0060] The flow rate of the inert gas flow is 50-200mL / min.

[0061] Step 3: The titanium nitride electrode obtained in step 2 is immersed in a transition metal salt precursor solution to load transition metal hydroxide by hydrothermal reaction.

[0062] The transition metal salt precursor solution is one or two of a cobalt salt, a nickel salt, and an iron salt, and an ultrapure water solution of urea and ammonium fluoride, wherein the concentration of the cobalt salt, the nickel salt, and the iron salt is 0.01-0.15M, the concentration of urea is 0.05-0.2M, and the concentration of ammonium fluoride is 0.1-0.4M;

[0063] The hydrothermal reaction temperature is 120-150℃, and the hydrothermal reaction time is 10-16h.

[0064] Step 4: The product obtained in step 3 is subjected to low-temperature phosphating treatment in an inert atmosphere to obtain a titanium nitride / transition metal phosphide composite electrode.

[0065] The inert gas is any one of nitrogen or argon;

[0066] The phosphorus source during the phosphating is sodium hypophosphite, and the mass used is 0.5-1.0g;

[0067] The phosphating treatment temperature is 300-350℃, the selenization time is 1-2h, and the heating rate is 2-5℃ / min;

[0068] The flow rate of the inert gas flow is 50-200mL / min.

[0069] Through the above steps, the titanium nitride / transition metal phosphide heterojunction electrode with a nano array structure prepared by the application can be efficiently and stably applied to the seawater electrolysis hydrogen production process, and provides a core component with excellent performance for the practical promotion of the seawater electrolysis hydrogen production technology.

[0070] The application will be further described below in combination with specific examples and comparative examples.

[0071] Example 1

[0072] The preparation method of the titanium nitride / transition metal phosphide heterojunction electrode with a nano array structure provided by the embodiment comprises the following steps:

[0073] 1. The carbon paper (CP) is ultrasonically cleaned several times with hydrochloric acid, acetone, ethanol and ultrapure water, and then dried in a vacuum oven at 60℃. Next, 1.5 mL of tetrabutyl titanate is uniformly mixed with 20 mL of hydrochloric acid and 20 mL of acetone. The above uniform solution is transferred into a high-pressure reaction kettle (50 mL) together with the CP, and is incubated in an oven at 200℃ for 2 hours. After the oven is cooled to room temperature, the electrode is taken out of the reaction kettle, washed with deionized water several times, and then dried in an air oven at 60℃.

[0074] 2. The electrode synthesized in step 1 is placed in a tube furnace together with melamine powder (1 g), wherein the melamine is located upstream of the tube furnace. Subsequently, the temperature of the tube furnace is increased to 800℃ at a rate of 5℃ min -1 , incubated for two hours under a nitrogen atmosphere, and naturally cooled to room temperature.

[0075] 3. 0.5 mmol of Co(NO3)2·6H2O, 0.5 mmol of Fe(NO3)3·9H2O, 3 mmol of urea and 7.5 mmol of ammonium fluoride are dissolved in 30 mL of ultrapure water. After being stirred gently for 30 min, the TiN / CP synthesized in step 2 is immersed in the above solution, transferred into a high-pressure reaction kettle (50 mL), heated at 120℃ for 6 h, and the obtained sample is taken out of the solution. After being washed with deionized water and ethanol several times, FeCo-LDH / TiN / CP is obtained.

[0076] 4. FeCo-LDH / TiN / CP and 0.5 g of sodium hypophosphite are placed in a tube furnace, wherein the sodium hypophosphite is located upstream of the tube furnace. Under an argon atmosphere, the temperature is increased to 350℃ at a rate of 5℃ min -1 , and incubated for 1 h to obtain a FeCoP / TiN / CP electrode.

[0077] Example 2

[0078] The preparation method of the titanium nitride / transition metal phosphide heterojunction electrode of the nano-array structure provided in the embodiment is the same as that in Embodiment 1, except that 0.5 mmol of Fe(NO3)3·9H2O is added to the hydrothermal precursor solution in step 3 in Embodiment 1.

[0079] Embodiment 3

[0080] The preparation method of the titanium nitride / transition metal phosphide heterojunction electrode of the nano-array structure provided in the embodiment is the same as that in Embodiment 1, except that 0.5 mmol of Co(NO3)2·6H2O is added to the hydrothermal precursor solution in step 3 in Embodiment 1.

[0081] Comparative Example 1

[0082] Preparation of a titanium nitride electrode: The carbon paper (CP) was ultrasonically cleaned several times with hydrochloric acid, acetone, ethanol and ultrapure water, and then dried in a vacuum oven at 60°C. Next, 1.5 mL of tetrabutyl titanate was uniformly mixed with 20 mL of hydrochloric acid and 20 mL of acetone. The above uniform solution was transferred into a high-pressure reaction kettle (50 mL) together with the CP, and incubated in an oven at 200°C for 2 hours. After the oven cooled to room temperature, the electrode was taken out of the reaction kettle, washed several times with deionized water, and then dried in an air oven at 60°C. The synthesized sample was placed in a tube furnace together with melamine powder (1 g), with the melamine located upstream of the tube furnace. Subsequently, the temperature of the tube furnace was increased at a rate of 5°C min -1 to 800°C, incubated for two hours under a nitrogen atmosphere, and naturally cooled to room temperature to obtain a titanium nitride electrode.

[0083] Comparative Example 2

[0084] Preparation of a cobalt iron phosphide electrode: The carbon paper (CP) was ultrasonically cleaned several times with hydrochloric acid, acetone, ethanol and ultrapure water, and then dried in a vacuum oven at 60°C. 0.5 mmol of Co(NO3)2·6H2O, 0.5 mmol of Fe(NO3)3·9H2O, 3 mmol of urea and 7.5 mmol of ammonium fluoride were dissolved in 30 mL of ultrapure water. After gentle stirring for 30 min, the CP was immersed in the above solution and transferred into a high-pressure reaction kettle (50 mL), heated at 120°C for 6 h, and the obtained sample was taken out of the solution, washed several times with deionized water and ethanol, and then dried. The sample and 0.5 g of sodium hypophosphite were placed in a tube furnace, with the sodium hypophosphite located upstream of the tube furnace. Under an argon atmosphere, the temperature was increased at a rate of 5°C min -1 to 350°C, and incubated for 1 h to obtain a cobalt iron phosphide electrode.

[0085] To verify the technical effects of the embodiments and comparative examples, the following experiments were performed.

[0086] Material characterization analysis:

[0087] 1. Microscopic morphology (corresponding to) Figure 1 )

[0088] like Figure 1 As shown, scanning electron microscopy (SEM) images confirm the successful fabrication of the multi-scale hierarchical titanium nitride / transition metal phosphide composite electrode of Example 1. The multi-scale hierarchical nanoarray structure of the titanium nitride / transition metal phosphide heterojunction electrode maximizes the exposure of active sites while enhancing mass transfer capacity, making it suitable for high-salinity and complex seawater environments.

[0089] 2. Phase composition analysis (corresponding to) Figure 2 )

[0090] XRD pattern of Example 1 ( Figure 2 The diffraction peaks at 36.7°, 42.6°, and 61.8° are attributed to TiN (PDF#38-1420), while the XRD diffraction peaks at 23.7°, 31.6°, and 48.1° correspond to CoP (PDF#29-0497). The diffraction peaks at 34.5°, 46.9°, and 56.0° match well with FeP (PDF#39-0809), demonstrating the successful preparation of iron-cobalt phosphide / titanium nitride.

[0091] 3. Wettability and air release capacity (corresponding) Figures 3-4 )

[0092] The titanium nitride / transition metal phosphide composite electrode with a nanoarray structure synthesized in Example 1 exhibits excellent wettability and degassing properties in seawater, with a water contact angle of 0°. Figure 3 a) The bubble contact angle is 147° ( Figure 3 (b) This facilitates the rapid release of bubbles in seawater. The rapid release of bubbles reduces the local pH increase caused by bubble retention and causes physical damage to the electrode surface, thereby minimizing the formation of Ca(OH)2 and Mg(OH)2. Figure 4 This conclusion was further verified in Example 1, using a small current (-10mAcm). -2 ) and high current (-100mAcm) -2 Small and uniform bubbles were observed to overflow at all hydrogen evolution current densities. This rapid bubble release helps hydrogen gas to leave the electrode surface quickly, thereby mitigating catalyst deactivation caused by the bubble shielding effect.

[0093] 4. Electrochemical performance analysis (corresponding to) Figure 5 )

[0094] The HER performance of Examples 1-3 and Comparative Examples 1 and 2 was tested using a standard three-electrode system in 1M KOH + seawater electrolyte. Figure 5 Example 1 exhibited optimal HER activity at an industrial current density of 500 mA / cm². -2 1Acm -2 The overpotential was only 152,273 mV, which is significantly better than the HER performance of other samples.

[0095] 5. Stability verification (corresponding) Figure 6 )

[0096] Constant current testing was performed using a standard three-electrode system. Figure 6 The results show that Example 1 was tested at 500 mA cm⁻¹ in an environment of 1M KOH + seawater. -2 It operated stably for over 340 hours at high current density with overpotential fluctuations of <5%, demonstrating excellent tolerance to seawater conditions and highlighting its potential as an industrial seawater hydrogen evolution catalyst.

[0097] 6. Resistance to calcium / magnesium precipitation (corresponding) Figure 7 )

[0098] Rich in Ca in natural seawater 2+ / Mg 2+ Hydroxides will precipitate at the cathode. These precipitates can adhere to or even completely cover / block the active sites, thereby impairing the hydrogen evolution performance of the cathode catalyst. A standard three-electrode system at 500 mA / cm²... -2 After reacting in natural seawater for 3 hours, the surface of Example 1 remained clean, indicating its excellent resistance to seawater sedimentation.

[0099] In summary, the nanoarray structure of titanium nitride / transition metal phosphide composite electrode prepared by this invention exhibits excellent HER activity and stability in alkaline seawater, providing a low-cost and high-durability solution for direct hydrogen production from seawater. This can promote the industrialization of marine hydrogen energy and is particularly suitable for off-grid hydrogen production scenarios coupled with wind power / photovoltaics.

Claims

1. A titanium nitride / transition metal phosphide heterojunction electrode with a nanoarray structure, characterized in that, The electrode comprises: a) a conductive substrate; b) titanium nitride grown on the conductive substrate; c) a transition metal phosphide loaded on the surface of the titanium nitride to form a heterojunction electrode with the titanium nitride; d) the electrode has a multi-scale hierarchical nanoarray structure, which is composed of multiple nanoscale components of different sizes.

2. The electrode according to claim 1, wherein the conductive substrate is one of carbon paper and carbon cloth.

3. The electrode according to claim 1, wherein the transition metal phosphide is a cobalt phosphide, a nickel phosphide, an iron phosphide, or a combination thereof.

4. The electrode according to claim 1, wherein the nanoarray structure is composed of micron- to nanometer-scale components and has a good porous structure to promote the transport of reactants and reduce resistance.

5. A method for preparing the titanium nitride / transition metal phosphide heterojunction electrode with the nanoarray structure according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: A solution A is obtained by thoroughly mixing a titanium source with an organic solvent. The conductive substrate is then immersed in solution A and dried, followed by annealing in a muffle furnace to successfully load TiO2 seeds onto the conductive substrate. Subsequently, a solution B is obtained by thoroughly mixing a titanium source with a solvent. The aforementioned electrode is then placed in solution B for hydrothermal reaction to prepare a TiO2 nanoarray electrode. Step 2: The TiO2 electrode obtained in Step 1 is subjected to high-temperature nitriding treatment in an inert atmosphere to obtain a titanium nitride electrode. Step 3: Immerse the titanium nitride electrode obtained in Step 2 in a transition metal salt precursor solution and load the transition metal hydroxide through a hydrothermal reaction. Step 4: The product obtained in Step 3 is subjected to low-temperature phosphating treatment in an inert atmosphere to obtain a titanium nitride / transition metal phosphide composite electrode.

6. The preparation method according to claim 5, characterized in that: In step 1, the conductive substrate (carbon paper or carbon cloth) is cut to an area of ​​2cm*3cm and needs to be pretreated: it is washed with acetone, ethanol and ultrapure water for 15-25 minutes in sequence, and then dried at 50-70℃. Solution A is an isopropanol solution of titanium n-butoxide, with a concentration of titanium n-butoxide of 0.04-0.08 M. The calcination temperature of the muffle furnace is 350-450℃, and the calcination time is 1-2 hours. Solution B is a mixed solution of titanium n-butoxide, hydrochloric acid, and acetone, wherein the volume fraction of titanium n-butoxide is 3-8%. The hydrothermal reaction temperature is 180-200℃, and the hydrothermal reaction time is 2-3 hours.

7. The preparation method according to claim 5, characterized in that: In step 2, the inert gas is either nitrogen or argon. The nitrogen source used during nitriding is melamine, with a mass of 0.8-1.2 g. The nitriding treatment temperature is 700-800℃; The nitriding time is 2–3 hours; The heating rate is 3-5℃ / min; The inert gas flow rate is 50–200 mL / min.

8. The preparation method according to claim 5, characterized in that: In step 3, the transition metal salt precursor solution is an ultrapure aqueous solution of one or two of cobalt salt, nickel salt, and iron salt with urea and ammonium fluoride, wherein the concentration of cobalt salt, nickel salt, and iron salt is 0.01-0.15M, the concentration of urea is 0.05-0.2M, and the concentration of ammonium fluoride is 0.1-0.4M. The hydrothermal reaction temperature is 120-150℃, and the hydrothermal reaction time is 10-16h.

9. The preparation method according to claim 5, characterized in that: In step 4, the inert gas is either nitrogen or argon. The phosphorus source used during phosphating is sodium hypophosphite, with a mass of 0.5-1.0 g. The phosphating treatment temperature is 300-350℃; The phosphating time is 1-2 hours; The heating rate is 2–5 °C / min; The inert gas flow rate is 50–200 mL / min.

10. The electrode according to claim 1, wherein the titanium nitride / transition metal phosphide heterojunction electrode with the nanoarray structure can achieve high current density seawater hydrogen evolution reaction at a low voltage, while maintaining long-term stability at a high current density, and has high Faraday efficiency and good commercial application value.

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