CN117660985A - Preparation of a Prussian blue analog-modified transition metal phosphide and its application in electrolyzing water for hydrogen production - Google Patents

Abstract

The invention discloses a preparation method of Prussian blue analogue modified transition metal phosphide and application of the Prussian blue analogue modified transition metal phosphide in hydrogen production by water electrolysis. A preparation method of transition metal phosphide comprises the following steps: transition metal salt, alkaline precipitant and NH ₄ F, dissolving in deionized water, stirring to obtain a first solution, and performing hydrothermal reaction to obtainA first precipitate; dissolving potassium ferricyanide in deionized water, and stirring to form a second solution; placing the first precipitate in a second solution, and performing ion exchange to obtain a second precipitate; and placing the second precipitate in a tube furnace, and calcining and phosphating under an inert atmosphere by using a phosphorus source to obtain the transition metal phosphide. The invention uses Prussian blue analogues to load on the surface of the catalyst in the form of small particles, prevents the sintering and agglomeration of the catalyst in the phosphating process by the limitation of the small-size particles in the nano structure, provides enough channels for mass transfer, and the prepared transition metal phosphide has excellent electrolytic water hydrogen evolution catalytic performance.

Description

Preparation of a Prussian blue analog-modified transition metal phosphide and electrolysis of water Hydrogen production applications

Technical field

The invention relates to the fields of nanomaterials and electrochemical catalysis, and specifically relates to the preparation of a Prussian blue analog-modified transition metal phosphide and its application in electrolyzing water for hydrogen production.

Background technique

As a green and environmentally friendly renewable energy, hydrogen (H ₂ ) has the advantages of wide sources, easy storage and transportation, and high energy density. The only product of hydrogen combustion is environmentally harmless H ₂ O, which avoids the need for Serious environmental problems caused by the emission of greenhouse gases such as _CO2 . Hydrogen production by electrolysis of water (HER) is a green and sustainable hydrogen production method that uses external electric energy to directly decompose water molecules into oxygen molecules and hydrogen molecules. The product has high purity.

As for effective catalysts for hydrogen evolution in electrolytic water, although precious metal Pt, Ru and other catalysts have high activity and are at the top of the HER activity volcano diagram, their high price and low storage capacity on earth have violated the concept of green hydrogen evolution. Therefore, it is necessary to find efficient and stable non-noble metal-based electrocatalysts to promote HER. Among them, transition metal phosphides (TMPs) have been widely reported and used in recent years due to their unique ability of P atoms to capture H*, which can effectively optimize the bonding strength between the catalyst and H*, thereby improving the electrochemical activity of the catalyst.

At present, many transition metal phosphides with low price, excellent performance and good stability have been developed. However, the problem of catalyst sintering is a common problem in the preparation of TMPs using the calcined phosphating method. Therefore, it is necessary to develop a simple and effective preparation method for sintering-free transition metal phosphide catalysts that is compatible with its excellent hydrogen evolution performance in water electrolysis.

Contents of the invention

In order to overcome the problems of the prior art, the present invention provides a method for preparing transition metal phosphide by hydrothermal method, anion exchange method and low-temperature phosphating and its application in electrolyzing water for hydrogen production.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

The invention provides a preparation method of transition metal phosphide, which includes the following steps:

(1) Dissolve the transition metal salt, alkaline precipitant, and NH ₄ F in deionized water, and stir to obtain the first solution;

(2) subject the first solution to a hydrothermal reaction to obtain a first precipitate;

(3) Dissolve potassium ferricyanide in deionized water and stir to form a second solution; place the first precipitate in the second solution and perform ion exchange to obtain the second precipitate;

(4) Place the second precipitate in a tube furnace, and use a phosphorus source to perform calcining and phosphating in an inert atmosphere to obtain the transition metal phosphide.

Preferably, the copper foam is immersed in the first solution, a first precipitate is obtained on the copper foam, and then subsequent steps are performed.

Preferably, the molar ratio of the transition metal salt, alkaline precipitant, and NH ₄ F = 1: (2-3): (1.5-2.5).

Preferably, the transition metal salt includes at least one of iron salt, cobalt salt, and nickel salt; and the alkaline precipitating agent is urea.

When the transition metal salt is Fe salt, the first precipitate is FeCO ₃ (OH) ₄ , and its structure is a thick nanosheet morphology; when the transition metal salt is Ni salt, the first precipitate is NiCO ₃ (OH) ₄ , and its structure is a thin nanosheet morphology; when the transition metal salt is used as the salt is Co salt or Ni salt and Co salt are mixed, the first precipitate is CoCO ₃ (OH) ₄ Or (NiCo)CO ₃ (OH) ₄ , whose structure is nanowire morphology.

It should be noted that in the entire synthesis step, if step (3) is omitted, that is, the first precipitate obtained from step (2) is directly phosphated in step (4), the resulting transition metal phosphide will suffer from severe sintering. According to past experience, it has a negative impact on its electrocatalytic activity.

Preferably, in step (2), the temperature of the hydrothermal reaction is 110-130°C, and the time of the hydrothermal reaction is >8 h.

Preferably, in step (2), after the hydrothermal reaction, vacuum drying is performed after cooling to room temperature to obtain the first precipitate; further preferably, the vacuum drying temperature is ≥60°C, and the drying time is 12-24h. .

Preferably, in step (3), the concentration of the second solution is 2.0-4.0 mmol/L.

Preferably, in step (3), the ion exchange temperature is 60-80°C, and the ion exchange time is 22-26 hours.

Preferably, in step (4), the temperature of the calcined phosphating is 300-400°C, the time of calcined phosphating is 0.8-1.2h, and the heating rate of calcined phosphating is 1.5-2.5°C/min; further preferably, The temperature of the calcined phosphating is 320-380°C, the time of the calcined phosphating is 0.8-1.2h, and the temperature rise rate of the calcined phosphating is 2°C/min.

Preferably, in step (4), the phosphorus source is sodium hypophosphite.

Preferably, in step (4), the inert atmosphere is Ar and N ₂ mixed gas.

A second aspect of the present invention provides a transition metal phosphide prepared by the preparation method of a transition metal phosphide.

The third aspect of the present invention provides the application of the transition metal phosphide in electrolyzing water to produce hydrogen.

Compared with the prior art, the beneficial effects of the present invention are:

The present invention provides a method for effectively inhibiting the sintering of the catalyst during the phosphating process. The key to this method is that the Prussian blue analogue Fe PBA is loaded on the surface of the catalyst in the form of small particles, which can be limited by the small-sized particles in the nanostructure. , prevent sintering and agglomeration of the catalyst during the phosphating process, and provide sufficient channels for mass transfer. The advantage is that compared to hydrothermal reactions, the reaction conditions are mild and simple. The anion exchange reaction is carried out at 60 to 80°C, and the transition metal phosphide prepared has excellent catalytic properties for electrolyzing water and hydrogen evolution.

Description of drawings

Figure 1 shows the SEM images of PBA-FeP/FeP@CF and FeP@CF;

Figure 2 shows the SEM images of FeP/CoP@CF and CoP@CF;

Figure 3 shows the SEM images of FeP/NiP@CF and NiP@CF;

Figure 4 shows the SEM images of FeP/NiCoP@CF and NiCoP@CF;

Figure 5 shows the electrochemical hydrogen evolution linear scan curve (HER-LSV) of PBA-FeP/FeP@CF and FeP@CF;

Figure 6 shows the electrochemical hydrogen evolution linear scan curve (HER-LSV) of FeP/CoP@CF and CoP@CF;

Figure 7 shows the electrochemical hydrogen evolution linear scan curve (HER-LSV) of FeP/NiP@CF and NiP@CF;

Figure 8 shows the electrochemical hydrogen evolution linear scan curve (HER-LSV) of FeP/NiCoP@CF and NiCoP@CF.

Detailed ways

The specific embodiments of the present invention will be further described below. It should be noted here that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The experimental methods in the following examples, unless otherwise specified, are all conventional methods. The test materials used in the following examples, unless otherwise specified, can be purchased through conventional commercial channels.

Example 1

This embodiment provides a method for synthesizing a PBA-FeP/FeP@CF (copper foam) composite electrocatalytic hydrogen evolution catalyst, which includes the following steps:

S1. Weigh 6 mmol of hydrated Fe(NO ₃ ) ₃ salt as the Fe source, 14.2 mmol of urea as the alkaline precipitant, and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water, and stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate Fe ₂ (CO ₃ ) ₃ (OH) ₄ @CF (FeCH@CF) precipitated on the copper foam.

S3. Dissolve 0.125g potassium ferricyanide in 150mL deionized water and stir evenly to form a second solution.

S4. Place the first precipitate FeCH@CF obtained in S2 into the second solution, and perform ion exchange at a temperature of 60°C to obtain the second precipitate FePBA/FeCH@CF.

S5. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the second precipitate obtained in S3 downstream of the tube furnace and perform calcining and phosphating under an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and a PBA-FeP/FeP@CF composite electrode was obtained.

Comparative example 1

In order to reflect the strategy proposed by the present invention to inhibit the sintering of phosphide through Prussian blue Fe cube particles, the following comparative examples are also provided, and the specific implementation steps are as follows:

S1. Weigh 6 mmol of hydrated Fe(NO ₃ ) ₃ salt as the Fe source, 14.2 mmol of urea as the alkaline precipitant, and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water, and stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate Fe ₂ (CO ₃ ) ₃ (OH) ₄ @CF (FeCH@CF) precipitated on the copper foam.

S3. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the first precipitate obtained in S2 downstream of the tube furnace and perform calcining and phosphating in an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and a FeP@CF composite electrode was obtained.

Structure Characterization:

The PBA-FeP/FeP@CF obtained in Example 1 and the FeP@CF obtained in Comparative Example 1 were characterized by scanning electron microscopy (SEM). The results are shown in Figure 1. It can be seen from Figure 1 that in the Fe PBA small particles Under the limitation of , the prepared catalyst did not sinter (Fig. 1a), while the catalyst without supporting Fe PBA suffered severe sintering during the phosphating process (Fig. 1b).

Performance Characterization:

Graphite rods were used as counter electrodes, Ag/AgCl (3.5M KCl, 0.2046V vs. RHE) as reference electrodes, and PBA-FeP/FeP@CF obtained in Example 1 and FeP@CF obtained in Comparative Example 1 (test area 1×1cm ² ) is the working electrode. Use electronic grade potassium hydroxide reagent to prepare a 1.0M KOH alkaline solution as the electrolyte. Before the hydrogen evolution (HER) performance test of electrolyzed water, N ₂ was introduced into the electrolyte for 30 min respectively to make it reach a saturated state. The resulting test results were potential converted using the Nernst equation to potential relative to the reversible hydrogen electrode (RHE). Linear scan voltammetry (LSV) was tested in a nitrogen-saturated electrolyte at a scan rate of 1mV s ^-1 . The results are shown in Figure 5. From Figure 5, it can be seen that the hydrogen evolution performance of the PBA-FeP/FeP@CF sample Far better than pure FeP@CF, the overpotentials at 100mAcm ^-2 are 236mV and 320mV respectively, which shows that phosphating sintering is an important factor affecting electrocatalytic water splitting and hydrogen evolution.

Example 2

This embodiment provides a synthesis method of FeP/CoP@CF (copper foam) composite electrocatalytic hydrogen evolution catalyst, which includes the following steps:

S1. Dissolve 6 mmol of hydrated Co(NO ₃ ) ₂ salt as the Co source, 14.2 mmol of urea as the alkaline precipitant, and 11.4 mmol of NH ₄ F in 50 mL of deionized water in sequence, and stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate CoCO ₃ (OH) ₄ @CF (CoCH@CF) precipitated on the copper foam.

S3. Dissolve 0.125g potassium ferricyanide in 150mL deionized water and stir evenly to form a second solution.

S4. Place the first precipitate CoCH@CF obtained in S2 into the second solution, and perform ion exchange at a temperature of 60°C to obtain the second precipitate Fe PBA/CoCH@CF.

S5. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the second precipitate obtained in S3 downstream of the tube furnace and perform calcining and phosphating under an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and the FeP/CoP@CF composite electrode was obtained.

Comparative example 2

In order to reflect the strategy proposed by the present invention to inhibit the sintering of phosphide through Prussian blue Fe cube particles, the following comparative examples are also provided, and the specific implementation steps are as follows:

S1. Weigh 6 mmol of hydrated Co(NO ₃ ) ₂ salt as the Co source, 14.2 mmol of urea as the alkaline precipitant and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water, stir evenly to obtain the first solution;

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate CoCO ₃ (OH) ₄ @CF (CoCH@CF) precipitated on the copper foam.

S3. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the first precipitate obtained in S2 downstream of the tube furnace and perform calcining and phosphating in an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and a CoP@CF composite electrode was obtained.

Structure Characterization:

The FeP/CoP@CF obtained in Example 2 and the CoP@CF obtained in Comparative Example 2 were characterized by scanning electron microscopy (SEM). The results are shown in Figure 2. It can be seen from Figure 2 that under the limitation of small Fe PBA particles, The prepared FeP/CoP@CF catalyst did not sinter (Fig. 2a), while the CoP@CF catalyst without Fe PBA was severely sintered during the phosphating process (Fig. 2b).

Performance Characterization:

Graphite rods were used as counter electrodes, Ag/AgCl (3.5M KCl, 0.2046V vs. RHE) as reference electrodes, and the FeP/CoP@CF obtained in Example 2 and the CoP@CF obtained in Comparative Example 2 (the test area was 1 ×1cm ² ) is the working electrode. Use electronic grade potassium hydroxide reagent to prepare a 1.0M KOH alkaline solution as the electrolyte. Before the hydrogen evolution (HER) performance test of electrolyzed water, N ₂ was introduced into the electrolyte for 30 min respectively to make it reach a saturated state. The resulting test results were potential converted using the Nernst equation to potential relative to the reversible hydrogen electrode (RHE). Linear scan voltammetry (LSV) was tested in a nitrogen-saturated electrolyte at a scan rate of 1mV s ^-1 . The results are shown in Figure 6. From Figure 6, it can be seen that the hydrogen evolution performance of the FeP/CoP@CF sample is much better than For pure CoP@CF, the overpotentials at 100mA cm ^-2 are 163mV and 193mV respectively, and the high current performance of FeP/CoP@CF is more prominent, which shows that phosphating sintering greatly hinders the catalyst's ability to operate at large current densities. hydrogen evolution activity.

Example 3

This embodiment provides a synthesis method of FeP/NiP@CF (copper foam) composite electrocatalytic hydrogen evolution catalyst, which includes the following steps:

S1. Weigh 6 mmol of hydrated Ni(NO ₃ ) ₂ salt as the Ni source, 14.2 mmol of urea as the alkaline precipitant, and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water, and stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate NiCO ₃ (OH) ₄ @CF (NiCH@CF) precipitated on the copper foam.

S3. Dissolve 0.125g potassium ferricyanide in 150mL deionized water and stir evenly to form a second solution.

S4. Place the first precipitate NiCH@CF obtained in S2 into the second solution, and perform ion exchange at a temperature of 60°C to obtain the second precipitate Fe PBA/NiCH@CF.

S5. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the second precipitate obtained in S3 downstream of the tube furnace and perform calcining and phosphating under an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and the FeP/NiP@CF composite electrode was obtained.

Comparative example 3

In order to reflect the strategy proposed by the present invention to inhibit the sintering of phosphide through Prussian blue Fe cube particles, the following comparative examples are also provided, and the specific implementation steps are as follows:

S1. Weigh 6 mmol of hydrated Ni(NO ₃ ) ₂ salt as the Ni source, 14.2 mmol of urea as the alkaline precipitant, and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water, and stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate NiCO ₃ (OH) ₄ @CF (NiCH@CF) precipitated on the copper foam.

S3. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the first precipitate obtained in S2 downstream of the tube furnace and perform calcining and phosphating in an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and a NiP@CF composite electrode was obtained.

Structure Characterization:

The FeP/NiP@CF obtained in Example 3 and the NiP@CF obtained in Comparative Example 3 were characterized by scanning electron microscopy (SEM). The results are shown in Figure 3. It can be seen from Figure 3 that the small Fe PBA particles are well embedded in the NiP nanosheets. Under the limitation of small size particles, the prepared FeP/NiP@CF catalyst basically does not sinter (Figure 3a) , while the NiP@CF catalyst without Fe PBA showed severe sintering during the phosphating process (Fig. 3b).

Performance Characterization:

Graphite rods were used as counter electrodes, Ag/AgCl (3.5M KCl, 0.2046V vs. RHE) as reference electrodes, and the FeP/NiP@CF obtained in Example 3 and the NiP@CF obtained in Comparative Example 3 (the test area was 1 ×1cm ² ) is the working electrode. Use electronic grade potassium hydroxide reagent to prepare a 1.0M KOH alkaline solution as the electrolyte. Before the hydrogen evolution (HER) performance test of electrolyzed water, N ₂ was introduced into the electrolyte for 30 min respectively to make it reach a saturated state. The resulting test results were potential converted using the Nernst equation to potential relative to the reversible hydrogen electrode (RHE). Linear scan voltammetry (LSV) was tested in a nitrogen-saturated electrolyte at a scan rate of 1 mV s ^-1 . The results are shown in Figure 7. It can be seen from Figure 7 that the hydrogen evolution performance of the FeP/NiP@CF sample is much better than that of pure NiP@CF. The overpotentials at 100mA cm ^-2 are 190mV and 296mV respectively, and FeP/CoP@CF The high current performance is more prominent, which shows that phosphating sintering greatly hinders the hydrogen evolution activity of the catalyst at high current density.

Example 4

This embodiment provides a synthesis method of FeP/NiCoP@CF (copper foam) composite electrocatalytic hydrogen evolution catalyst, which includes the following steps:

S1. Weigh 4 mmol of hydrated Co(NO ₃ ) ₂ salt as Co source, 2 mmol of hydrated Ni(NO ₃ ) ₂ salt as Ni source, 14.2 mmol of urea as alkaline precipitant and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water. water, stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate (NiCo)CO ₃ (OH) ₄ @CF (NiCoCH@CF) precipitated on the copper foam.

S3. Dissolve 0.125g potassium ferricyanide in 150mL deionized water and stir evenly to form a second solution.

S4. Place the first precipitate NiCoCH@CF obtained in S2 into the second solution, and perform ion exchange at a temperature of 60°C to obtain the second precipitate Fe PBA/NiCoCH@CF@CF.

S5. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the second precipitate obtained in S3 downstream of the tube furnace and perform calcining and phosphating under an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and the FeP/NiCoP@CF composite electrode was obtained.

Comparative example 4

In order to reflect the strategy proposed by the present invention to inhibit the sintering of phosphide through Prussian blue Fe cube particles, the following comparative examples are also provided, and the specific implementation steps are as follows:

S1. Weigh 4 mmol of hydrated Co(NO ₃ ) ₂ salt as Co source, 2 mmol of hydrated Ni(NO ₃ ) ₂ salt as Ni source, 14.2 mmol of urea as alkaline precipitant and 11.4 mmol of NH ₄ F in order and dissolve them in 50 mL of deionized water. water, stir evenly to obtain the first solution.

S2. Transfer the first solution obtained in S1 to a 100 mL polytetrafluoroethylene reaction kettle, place the copper foam carrier vertically into the reaction kettle, react hydrothermally at 120°C for 10 hours, cool to room temperature, and continue at 60°C. Dry in a vacuum drying oven for 12 hours to obtain the first precipitate (NiCo)CO ₃ (OH) ₄ @CF (NiCoCH@CF) precipitated on the copper foam.

S3. Weigh 0.5g of sodium hypophosphite in the middle of the porcelain circumference and place it upstream of the tube furnace. Place the first precipitate obtained in S2 downstream of the tube furnace and perform calcining and phosphating in an _N2 inert atmosphere. The calcining temperature The temperature was 350°C, and the heating rate was 2°C/min, and a NiCoP@CF composite electrode was obtained.

Structure Characterization:

The FeP/NiCoP@CF obtained in Example 4 and the NiCoP@CF obtained in Comparative Example 4 were characterized by scanning electron microscopy (SEM). The results are shown in Figure 4. It can be seen from Figure 4 that under the limitation of small Fe PBA particles , the prepared FeP/NiCoP@CF catalyst did not sinter (Fig. 4a), while the NiCoP@CF catalyst without supporting Fe PBA suffered severe sintering during the phosphating process (Fig. 4b).

Performance Characterization:

Graphite rods were used as counter electrodes, Ag/AgCl (3.5M KCl, 0.2046V vs. RHE) as reference electrodes, and the FeP/NiCoP@CF obtained in Example 4 and the NiCoP@CF obtained in Comparative Example 4 (the test area was 1 ×1cm ² ) is the working electrode. Use electronic grade potassium hydroxide reagent to prepare a 1.0M KOH alkaline solution as the electrolyte. Before the hydrogen evolution (HER) performance test of electrolyzed water, N ₂ was introduced into the electrolyte for 30 min respectively to make it reach a saturated state. The resulting test results were potential converted using the Nernst equation to potential relative to the reversible hydrogen electrode (RHE). Linear scan voltammetry (LSV) was tested in a nitrogen-saturated electrolyte at a scan rate of 1mV s ^-1 . The results are shown in Figure 8. From Figure 8, it can be seen that the hydrogen evolution performance of the FeP/NiCoP@CF sample is much better than For pure NiCoP@CF, the overpotentials at 100mAcm ^-2 are 168mV and 170mV respectively, and this activity gap is more obvious when the current density is greater than 500mAcm ^-2 , which indicates that phosphating sintering hinders the hydrogen evolution activity of the catalyst at high current density.

In summary, the strategy proposed by the present invention to inhibit phosphating sintering is based on the small size effect of Prussian blue analogue Fe cubic particles. Its advantages are simple preparation and excellent sintering inhibition effect. At the same time, the introduced FeP component can be combined with AP Or phosphides such as ABP form a composite structure, thereby improving the electrocatalytic hydrogen evolution ability of the catalyst based on the multi-component effect and the electronic effect of the heterogeneous interface.

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the invention, and they still fall within the protection scope of the invention.

Claims (10)

1. The preparation method of the transition metal phosphide is characterized by comprising the following steps of:

(1) Transition metal salt, alkaline precipitant and NH ₄ F, dissolving in deionized water, and stirring to obtain a first solution;

(2) Carrying out hydrothermal reaction on the first solution to obtain a first precipitate;

(3) Dissolving potassium ferricyanide in deionized water, and stirring to form a second solution; placing the first precipitate in a second solution, and performing ion exchange to obtain a second precipitate;

(4) And placing the second precipitate in a tube furnace, and calcining and phosphating under inert atmosphere by using a phosphorus source to obtain the transition metal phosphide.

2. The method for producing a transition metal phosphide according to claim 1, wherein copper foam is immersed in the first solution to obtain a first precipitate on the copper foam, followed by a subsequent step.

3. The method for producing a transition metal phosphide according to claim 1 or 2, characterized in that the transition metal salt, alkaline precipitant, NH ₄ Molar ratio of F = 1: (2-3): (1.5-2.5).

4. A method of preparing a transition metal phosphide according to claim 3, wherein the transition metal salt comprises at least one of an iron salt, a cobalt salt, and a nickel salt; the alkaline precipitant is urea.

5. The method for producing a transition metal phosphide according to claim 1 or 2, wherein in step (2), the hydrothermal reaction is carried out at a temperature of 110 to 130 ℃ for a period of > 8 hours.

6. The method for producing a transition metal phosphide according to claim 1 or 2, wherein the concentration of the second solution in step (3) is 2.0 to 4.0mmol/L.

7. The method for producing a transition metal phosphide according to claim 1 or 2, wherein in step (3), the ion exchange temperature is 60 to 80 ℃ and the ion exchange time is 22 to 26 hours.

8. The method for producing transition metal phosphide according to claim 1 or 2, wherein in step (4), the temperature of calcination and phosphating is 300-400 ℃, the time of calcination and phosphating is 0.8-1.2h, and the temperature rise rate of calcination and phosphating is 1.5-2.5 ℃/min.

9. A transition metal phosphide prepared by the process of any one of claims 1 to 8.

10. Use of the transition metal phosphide as defined in claim 9 in the production of hydrogen by electrolysis of water.