CN113388847B - Metal sulfide/nitrogen-doped carbon electrocatalyst derived from Prussian blue analogues and its preparation method and application - Google Patents

Abstract

A Prussian blue analogue derived metal sulfide/nitrogen-doped carbon electrocatalyst, a preparation method and application thereof. The invention takes cobalt iron Prussian blue analogue as a template, and prepares the non-noble metal sulfide cubic cage-shaped nano composite catalyst by ammonia water etching and gas phase vulcanization. The catalyst has CoS ₂ ‑FeS ₂ The nitrogen-doped carbon heterostructure is in a cubic pore structure, has high porosity and good conductivity, and has excellent hydrogen evolution and oxygen evolution electrocatalytic activity in an alkaline medium. The excellent catalytic performance is mainly due to the enhanced conductivity of nitrogen-doped carbon; coS ₂ ‑FeS ₂ The nitrogen-doped carbon heterostructure changes the electronic structure of a heterostructure, improves the conductivity of the heterostructure and is more beneficial to the conduction of electrons; the compounding of the nitrogen-doped carbon matrix increases the stability of the catalyst, promotes the effective transfer of electrons between the metal sulfide and the carbon matrix, and greatly improves the electrocatalytic performance of the material.

Description

Metal sulfide/nitrogen-doped carbon electrocatalysts derived from Prussian blue analogues and their Preparation method and application

Technical field:

The invention belongs to the field of new energy material technology and electrochemical catalysis, and specifically relates to a metal sulfide/nitrogen-doped carbon electrocatalyst derived from a Prussian blue analogue; it also relates to a preparation method of the catalyst and its oxygen evolution reaction at the anode of electrolyzed water, Cathodic hydrogen evolution reaction in electrolyzed water and electrocatalytic applications in total water splitting.

Background technique:

Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are key electrode processes in water electrolysis technology, but both processes suffer from slow kinetics. At present, the catalysts used for HER are mainly Pt and its alloys, and the catalysts used for OER are mainly IrO ₂ and RuO ₂ , but these noble metals are scarce in nature, so it is very important to develop new high-efficiency and cheap electrocatalysts, among which carbon-based Non-noble metal catalysts are one of the most likely catalysts to replace the above-mentioned noble metals and have attracted extensive attention.

Prussian blue and its analogues are a class of porous crystalline materials with inherently high stability and high porosity, and are commonly used in efficient catalytic and separation processes. The cobalt-iron Prussian blue analog is formed by the reaction of cobalt nitrate hexahydrate and potassium ferricyanide, which can be used as a sacrificial template to prepare non-noble metal compound-porous carbon composites by high-temperature calcination, and the electronic properties and surface can be adjusted by heteroatom doping Polarity, improve the electrochemical catalytic activity of the composite material. At present, the commonly used doping atoms are N, S, B, P, etc. These heteroatoms can change the electronic properties of carbon materials by replacing some sp ² hybridized carbon atoms in the graphite lattice, and further improve the catalytic performance of carbon materials. activity and stability. Although some achievements have been made in the preparation of porous carbon nanomaterials using Prussian blue analogues as precursors, metal sulfide/nitrogen doped The non-noble metal/carbon material cubic nanocomposite with carbon heterostructure and its bifunctional electrocatalytic performance for HER and OER have not been reported in the literature.

The invention uses the cobalt-iron Prussian blue analogue as a template, and prepares the non-precious metal sulfide cubic cage nano-carbon compound through ammonia water etching and gas phase vulcanization. Due to the porous framework structure of the cobalt-iron Prussian blue analogue, the non-noble metal sulfide/nitrogen-doped carbon material inherited its cubic pore structure after ammonia etching and gas-phase sulfidation. The obtained CoS ₂ -FeS ₂ /NC catalyst has high porosity, good electrical conductivity and catalytic activity, effectively reduces its OER and HER overpotential, and exhibits excellent long-term stability. This method has important theoretical and practical significance for the development of non-noble metal sulfide heteroatom-doped carbon composite electrocatalysts and energy conversion and storage devices.

Invention content:

In view of the deficiencies in the prior art and the needs of research and application in this field, one of the purposes of the present invention is to provide a metal sulfide/nitrogen-doped carbon electrocatalyst derived from Prussian blue analogs; As a template, CoS ₂ -FeS ₂ /nitrogen-doped carbon catalyst was obtained after ammonia etching and gas-phase sulfidation; wherein the cobalt-iron Prussian blue analog was denoted as CoFe-PBA, and the CoS ₂ -FeS ₂ /nitrogen-doped carbon catalyst was denoted as CoS ₂ -FeS ₂ /NC;

The second object of the present invention is to provide a method for preparing metal sulfide/nitrogen-doped carbon electrocatalysts derived from Prussian blue analogues, specifically comprising the following steps:

(a) Preparation of CoFe-PBA

Weigh 860mg Co(NO ₃ ) ₂ ·6H ₂ O and 1.32g sodium citrate and dissolve in 100mL deionized water, which is recorded as solution A; weigh 658mg potassium ferricyanide and dissolve it in another 100mL deionized water, which is recorded as Solution B; under stirring conditions, add solution B to solution A, stir for three minutes, centrifuge to collect samples after standing for 10 hours, wash with deionized water and absolute ethanol three times each, and dry at 50°C for 12 hours;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. The obtained cobalt-iron nanoframes are recorded as CoFe-NFs; 20 mg of the above-mentioned CoFe-NFs is weighed and placed in the lower end of the tube furnace in a magnetic boat, and 200-400 mg of sulfur powder is weighed and placed in the magnetic boat at the upper end of the tube furnace. Raise the temperature to 200-500°C at a rate of 2°C/min, and vulcanize in a nitrogen atmosphere for 1-5 hours to prepare the catalyst CoS ₂ -FeS ₂ /NC;

The metal sulfide/nitrogen-doped carbon electrocatalyst has a hollow nanocubic cage structure, and each element is evenly distributed on the edge of the cube. The average particle size of the _nanocubic cage unit of the catalyst is 100-200nm; ₂ The average particle size of the nanoparticles is 5-30nm, and they are evenly embedded on the nitrogen-doped carbon nanosheets.

The third object of the present invention is to provide a metal sulfide/nitrogen-doped carbon electrocatalyst derived from Prussian blue analogues for catalytic application in water electrolysis cathode HER and anode OER.

The present invention uses cobalt-iron Prussian blue analogues as templates to prepare non-precious metal sulfide cubic cage nanocomposite electrocatalysts through ammonia water etching and gas phase vulcanization; the heterostructure not only improves the conductivity of the catalyst, but also increases the number of active sites , and effectively reduce the overpotential of HER and OER, showing excellent long-term stability.

Compared with the prior art, the present invention has the following main advantages and beneficial effects:

1) The bifunctional electrocatalyst of the present invention is a non-precious metal composite material, and the raw materials used are easy to purchase, rich in resources and low in price, easy to operate, and convenient for large-scale production;

2) The bifunctional electrocatalyst described in the present invention is a non-precious metal sulfide/nitrogen-doped carbon material, which has better OER and HER catalytic activity, compared with the unilateral OER of non-precious metal/non-metal catalysts reported in current research Or HER activity has a significant advantage;

₃ ) Compared with the commercial RuO2 catalyst, the bifunctional electrocatalyst of the present invention has significantly improved stability and can maintain good catalytic activity in the long-term use of electrolysis of water technology.

Description of drawings:

Figure 1 is the scanning electron micrographs of CoFe-PBA (A) obtained in Example 1, CoFe-NFs (B) obtained in Example 1, CoS ₂ -FeS ₂ /NC (C) obtained in Example 1, and the CoS obtained in Example 1 ₂ -FeS ₂ /NC(D) transmission electron microscope image.

Fig. 2 is the XRD pattern of the CoS ₂ -FeS ₂ /NC catalyst obtained in Example 1.

Fig. 3 is the OER linear sweep voltammetry curves of CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1 and commercial RuO ₂ modified carbon cloth respectively.

Figure 4 shows the carbon cloth modified by CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1, NiS ₂ -FeS ₂ /NC obtained in Comparative Example 2 and MnS-FeS ₂ /NC obtained in Comparative Example 3 OER linear sweep voltammetry plot.

Fig. 5 is the OER constant voltage it (left) of the CoS ₂ -FeS ₂ /NC modified carbon cloth obtained in Example 1 and the linear sweep voltammetry curve (right) before and after 1500 cycles of cyclic voltammetry.

Fig. 6 is the HER linear sweep voltammetry curves of CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1 and commercial Pt/C modified carbon cloth respectively.

Figure 7 shows the carbon cloth modified by CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1, NiS ₂ -FeS ₂ /NC obtained in Comparative Example 2 and MnS-FeS ₂ /NC obtained in Comparative Example 3 HER linear sweep voltammetry curve.

Fig. 8 is the linear sweep voltammetry curve of the total water splitting performed on the CoS ₂ -FeS ₂ /NC non-noble metal electrocatalyst modified carbon cloth obtained in Example 1.

Fig. 9 is a constant voltage it test graph of CoS ₂ -FeS ₂ /NC non-noble metal electrocatalyst modified carbon cloth obtained in Example 1 at 1.61V.

detailed description:

In order to further understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings and examples, but the present invention is not limited in any way.

Example 1:

(a) Preparation of CoFe-PBA

Weigh 860mg of Co(NO ₃ ) ₂ ·6H ₂ O and 1.32g of sodium citrate and dissolve it in 100mL of deionized water, which is called solution A; then weigh 658mg of potassium ferricyanide and dissolve it in another 100mL of deionized water, Denote it as solution B; under the condition of stirring, add solution B to solution A, stir for three minutes, then let it stand for 10 hours, collect the sample by centrifugation, wash three times with deionized water and absolute ethanol, and dry at 50°C for 12 hours;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to At 400°C, sulfidation was maintained in a nitrogen atmosphere for 4 hours to prepare the catalyst CoS ₂ -FeS ₂ /NC;

Example 2:

(a) Preparation of CoFe-PBA

Prepared according to the method and conditions of step (a) in Example 1;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to 200°C, kept sulfide in nitrogen atmosphere for 4h, and prepared the catalyst CoS ₂ -FeS ₂ /NC;

Example 3:

(a) Preparation of CoFe-PBA

Prepared according to the method and conditions of step (a) in Example 1;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to 300°C, kept sulfide in nitrogen atmosphere for 4h, and prepared the catalyst CoS ₂ -FeS ₂ /NC;

Example 4:

(a) Preparation of CoFe-PBA

Prepared according to the method and conditions of step (a) in Example 1;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to 500°C, kept sulfide in nitrogen atmosphere for 4h, and prepared the catalyst CoS ₂ -FeS ₂ /NC;

Example 5:

(a) Preparation of CoFe-PBA

Prepared according to the method and conditions of step (a) in Example 1;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 200 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to At 400°C, sulfidation was maintained in a nitrogen atmosphere for 4 hours to prepare the catalyst CoS ₂ -FeS ₂ /NC;

Embodiment 6:

(a) Preparation of CoFe-PBA

Prepared according to the method and conditions of step (a) in Example 1;

(b) Preparation of CoS ₂ -FeS ₂ /NC

Disperse 20mg of Co-Fe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h. Obtain cobalt-iron nanoframe CoFe-NFs;

Weigh 20 mg of the CoFe-NFs and put it in a magnetic boat and place it at the lower end of the tube furnace, weigh 250 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, and raise the temperature at a rate of 2 °C/min to At 400°C, sulfidation was maintained in a nitrogen atmosphere for 4 hours to prepare the catalyst CoS ₂ -FeS ₂ /NC;

Comparative example 1:

(a) Preparation of FeFe-PB

Weigh 1.2g Fe(NO ₃ ) ₃ 6H ₂ O and 1.32g sodium citrate and dissolve in 100mL of deionized water, which is called solution A; then weigh 658mg of potassium ferricyanide and dissolve in another 100mL of deionized water , recorded as solution B;, under stirring conditions, add solution B to solution A, stir for three minutes, then centrifuge to collect samples after standing for 10 hours, then wash three times with deionized water and absolute ethanol, 50 ℃ drying for 12h.

(b) Preparation of FeS ₂ /NC

Disperse 20mg of Fe-Fe PB in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h , to obtain the iron-iron nanoframe; take 20mg of the iron-iron nanoframe and put it into the lower end of the tube furnace in a magnetic boat, weigh 300mg of sulfur powder and put it in the upper end of the tube furnace in the magnetic boat, thinking that 2 The heating rate of ℃/min was raised to 400 ℃, and the sulfidation was maintained in nitrogen atmosphere for 4 hours to prepare the catalyst FeS ₂ /NC;

Comparative example 2:

(a) Preparation of NiFe-PBA

Weigh 870mg of Ni(NO ₃ ) ₂ ·6H ₂ O and 1.32g of sodium citrate and dissolve in 100mL of deionized water, which is called solution A; then weigh 658mg of potassium ferricyanide and dissolve in another 100mL of deionized water, Denote it as solution B; under the condition of stirring, add solution B to solution A, stir for three minutes, then let it stand for 10 hours, collect the sample by centrifugation, wash three times with deionized water and absolute ethanol, and dry at 50°C for 12 hours;

(b) Preparation of NiS ₂ -FeS ₂ /NC

Disperse 20mg of NiFe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h to obtain nickel Iron nanoframe NiFe-NFs;

Weigh 20 mg of the NiFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, so as to raise the temperature at a rate of 2 °C/min to At 400°C, sulfidation was maintained in a nitrogen atmosphere for 4 hours to prepare the catalyst NiS ₂ -FeS ₂ /NC;

Comparative example 3:

(a) Preparation of MnFe-PBA

Weigh 500mg of MnSO ₄ ·H ₂ O and 1.32g of sodium citrate and dissolve it in 100mL of deionized water, which is called solution A; then weigh 658mg of potassium ferricyanide and dissolve it in another 100mL of deionized water, which is called solution B ; Under the condition of stirring, add solution B to solution A, stir for three minutes, then centrifuge to collect samples after standing for 10 hours, wash with deionized water and absolute ethanol three times, and dry at 50°C for 12 hours;

(b) Preparation of MnS-FeS ₂ /NC

Disperse 20mg of MnFe PBA in 50mL of ethanol, add it to 50mL of 25% ammonia solution, stir for 10min, collect the sample by centrifugation, wash with deionized water until the solution is nearly neutral, and dry at 60°C for 24h to obtain nickel Iron nanoframework MnFe-NFs;

Weigh 20 mg of the NiFe-NFs into a magnetic boat and place it at the lower end of the tube furnace, weigh 300 mg of sulfur powder and put it in the magnetic boat and place it at the upper end of the tube furnace, so as to raise the temperature at a rate of 2 °C/min to At 400°C, sulfidation was maintained in a nitrogen atmosphere for 4 hours to prepare the catalyst MnS-FeS ₂ /NC;

Figure 1 is the scanning electron micrographs of CoFe-PBA, CoFe-NFs and CoS ₂ -FeS ₂ /NC obtained in Example 1 (A), Example 1 (B), and Example 1 (C) respectively, and the CoS obtained in Example 1 ₂ -FeS ₂ /NC(D) transmission electron microscope image. It can be seen from Figure A that the crystal particles of CoFe-PBA are regular cubes, and CoFe-PBA has a good crystal shape. It can be seen from Figure B that the edges of the cubes of CoFe-PBA etched by ammonia water are destroyed, but the cube skeleton is basically maintained. Figures C and D show that the material maintains a cubic structure after gas-phase vulcanization, and Figure D shows that CoS ₂ -FeS ₂ is evenly distributed on the surface of the cube, presenting a hollow cage-like structure, which may be due to the gradual migration of internal components during high-temperature vulcanization to the external surface as a result.

Fig. 2 is the XRD pattern of the CoS ₂ -FeS ₂ /NC catalyst obtained in Example 1. By comparing with the standard card, it is found that the main components of the vulcanized sample are CoS ₂ and FeS ₂ , which correspond to the standard cards JCPDS41-1471 and JCPDS 42-1340 respectively. It shows that after ammonia etching and sulfidation, CoFe-PBA is transformed into a nitrogen-doped carbon-supported transition metal sulfide CoS ₂ -FeS ₂ heterostructure, which is conducive to the regulation of the electronic structure and the improvement of the electrocatalytic performance of the catalyst.

The above electrocatalytic performance tests all use the saturated Ag/AgCl electrode as the reference electrode, the Pt electrode as the counter electrode, the scan rate is 5mV/s, the electrolyte is 1M KOH, and the electrolyte needs to be saturated with _N2 before the OER catalytic performance test.

Fig. 3 is the OER linear sweep voltammetry curves of CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1 and commercial RuO ₂ modified carbon cloth respectively. It can be seen from the figure that when the current density reaches 10mA/cm ² , the existence of CoS ₂ -FeS ₂ /NC heterostructure has the lowest overpotential, indicating that the presence of transition metal sulfide CoS ₂ -FeS ₂ has a great influence on the OER performance of the catalyst It plays a synergistic promotion effect, further increases the active sites of carbon materials, improves the properties of the catalyst surface, and makes the electrochemical activity of CoS ₂ -FeS ₂ /NC better than that of single-phase metal sulfide FeS ₂ /NC.

Figure 4 shows the carbon cloth modified by CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1, NiS ₂ -FeS ₂ /NC obtained in Comparative Example 2 and MnS-FeS ₂ /NC obtained in Comparative Example 3 OER linear sweep voltammetry plot. Considering that the performance of transition metal cobalt sulfides combined with FeS ₂ as OER catalysts is greatly improved, in order to examine the catalytic performance of other transition metal sulfides and FeS ₂ when forming heterostructures, NiS ₂ -FeS ₂ were synthesized. /NC and MnS-FeS ₂ /NC two transition metal sulfides of Mn and Ni, as shown in Figure 4, compared four catalysts NiS ₂ -FeS ₂ /NC, MnS-FeS ₂ /NC, CoS ₂ -FeS ₂ /NC, the OER performance of FeS ₂ /NC in 1M KOH solution environment. It can be seen from the figure that the sulfide of transition metal Co still shows the best catalytic activity. For NiS ₂ -FeS ₂ /NC, when catalyzing OER, When the current density reaches 10mA/cm ² , the potential corresponding to 1.47Vvs.RHE, MnS-FeS ₂ /NC shows worse catalytic performance.

Fig. 5 is the OER stability test of the CoS ₂ -FeS ₂ /NC modified carbon cloth obtained in Example 1. The catalyst CoS ₂ -FeS ₂ /NC supported on carbon cloth, after 25 hours of stability test, the catalytic performance did not decline significantly. After 1500 cycles of CV testing, the LSV curves almost overlap, indicating the excellent long-term stability of the catalysts.

Fig. 6 is the HER linear sweep voltammetry curves of CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1 and commercial Pt/C modified carbon cloth respectively. It can be seen that the CoS ₂ -FeS ₂ /NC heterostructure has the lowest overpotential when the current density reaches 10 mA/cm ² , indicating that the presence of transition metal sulfide CoS ₂ -FeS ₂ synergistically promotes the OER performance of the catalyst. The effect further increases the active sites of carbon materials, improves the properties of the catalyst surface, and makes the electrochemical activity of CoS ₂ -FeS ₂ /NC better than that of single-phase FeS ₂ /NC.

Figure 7 shows the carbon cloth modified by CoS ₂ -FeS ₂ /NC obtained in Example 1, FeS ₂ /NC obtained in Comparative Example 1, NiS ₂ -FeS ₂ /NC obtained in Comparative Example 2 and MnS-FeS ₂ /NC obtained in Comparative Example 3 HER linear sweep voltammetry curve. Further examine the catalytic activity of NiS ₂ -FeS ₂ /NC and MnS-FeS ₂ /NC for HER, as shown in Figure 7, when the material NiS ₂ -FeS ₂ /NC reaches a current density of 10mA/cm ² The overpotential is 327mV, which is obviously higher than that of CoS ₂ -FeS ₂ /NC under the same conditions. When the current density of MnS-FeS ₂ /NC reaches 10mA/cm ² , the overpotential is 437mV, which is better than that of single-phase metal Fe sulfide FeS ₂ /NC.

Fig. 8 is the total water splitting linear sweep voltammetry curve of CoS ₂ -FeS ₂ /NC non-precious metal electrocatalyst modified carbon cloth obtained in Example 1. It can be seen from the figure that when the current density reaches 10mA/cm ² , the target catalyst The required potential is significantly smaller than that of the noble metal RuO ₂ , indicating that the CoS ₂ -FeS ₂ distribution at the cube edges is beneficial for the direct contact of the reactants or reaction intermediates with the active sites, thus enhancing the electrocatalytic performance.

Fig. 9 is a constant voltage it test graph of CoS ₂ -FeS ₂ /NC non-noble metal electrocatalyst modified carbon cloth obtained in Example 1 at 1.61V. It can be seen from the figure that in the 16h test, the performance of CoS ₂ -FeS ₂ /NC was only attenuated by 5.8%, showing good long-term stability of electrolyzed water, which is of great significance in the application of new energy in the future. The field of electrode materials for electrolysis of water technology has potential application value.

Claims (2)

1. The Prussian blue analogue derived metal sulfide/nitrogen-doped carbon electrocatalyst is characterized in that the catalyst takes a cobalt-iron Prussian blue analogue as a template, and CoS is obtained by ammonia etching and gas phase sulfidation ₂ -FeS ₂ A nitrogen-doped carbon catalyst; wherein the cobalt iron Prussian blue analogue is marked as CoFe-PBA，CoS ₂ -FeS ₂ the/N-doped carbon catalyst is denoted as CoS ₂ -FeS ₂ /NC；

The preparation method of the Prussian blue analogue derived metal sulfide/nitrogen-doped carbon electrocatalyst is characterized by comprising the following specific steps of:

(a) Preparation of CoFe-PBA

Weighing 860mg Co (NO) ₃ ) ₂ ·6H ₂ Dissolving O and 1.32g sodium citrate in 100mL deionized water, and marking as solution A; weighing 658mg potassium ferricyanide and dissolving in another 100mL deionized water, and marking as solution B; adding the solution B into the solution A under the condition of stirring, stirring for three minutes, standing for 10h, centrifuging to collect a sample, washing with deionized water and absolute ethyl alcohol for three times respectively, and drying at 50 ℃ for 12h;

(b) CoS ₂ - FeS ₂ preparation of/NC

Dispersing 20mg of Co-Fe PBA in 50mL ethanol, adding the Co-Fe PBA into an ammonia water solution with the concentration of 50mL being 25%, stirring and reacting for 10min, centrifuging to collect a sample, washing with deionized water until the solution is close to neutrality, and drying 24h at 60 ℃ to obtain a cobalt-iron nano frame which is marked as CoFe-NFs; weighing 20mg and the CoFe-NFs in a magnetic boat, placing the magnetic boat in the lower end of a tube furnace, weighing 200-400 mg of sulfur powder in the magnetic boat, placing the magnetic boat in the upper end of the tube furnace, heating to 200-500 ℃ at the speed of 2 ℃/min, and vulcanizing in a nitrogen atmosphere for 1-5 hours to obtain the catalyst CoS ₂ -FeS ₂ /NC；

The metal sulfide/nitrogen-doped carbon electrocatalyst is in a hollow nano cubic cage structure, elements are uniformly distributed on the edge of a cube, and the average grain diameter of nano cubic cage units of the catalyst is 100-200 nm; metal sulfide CoS ₂ -FeS ₂ The average grain diameter of the nano-particles is 5-30nm, and the nano-particles are uniformly embedded on the nitrogen-doped carbon nano-sheets.

2. The prussian blue analog-derived metal sulfide/nitrogen-doped carbon electrocatalyst according to claim 1, characterized in that the catalyst is used in the cathodic hydrogen evolution reaction and anodic oxygen evolution reaction of electrolysis of water.

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