Difunctional electro-catalytic water decomposition material as well as preparation and application thereof

Abstract

The invention belongs to the field of electro-catalytic materials, and particularly relates to a bifunctional electro-catalytic water decomposition material and preparation and application thereof.The preparation method includes the steps that a first MOF precursor material is subjected to a first-stage coordination reaction in a solution containing an auxiliary a and an auxiliary b, and a first MOF is obtained; the first MOF is used as a substrate, a second-stage coordination reaction is carried out on a second MOF precursor material in a solution of an auxiliary c, the second MOF is deposited on the first MOF, and a core-shell double-MOF material is prepared; performing heat treatment on the core-shell dual-MOF material to obtain a heat-treated material; and mixing the heat treatment material with a phosphorus source, carrying out phosphating roasting treatment, and putting a phosphating product into a liquid-phase cooling medium while the phosphating product is hot, and carrying out quenching treatment, so as to obtain the bifunctional electro-catalytic water decomposition material. The bifunctional electro-catalytic water decomposition material prepared by the preparation method disclosed by the invention has excellent HER and OER dual catalytic activity.

Description

Technical Field

[0001] The present invention belongs to the field of catalytic materials, and in particular relates to the technical field of catalytic materials for water electrolysis. Background Art

[0002] Water electrolysis converts electrical energy into chemical energy, specifically through the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER). Catalytic materials for water electrolysis typically include anode and cathode catalysts. Anode catalysts primarily participate in the oxidation reaction, generating oxygen; cathode catalysts primarily participate in the reduction reaction of hydrogen ions, generating hydrogen.

[0003] OER and HER reactions are different and require different catalytic materials. However, this will increase the cost of water electrolysis. Therefore, existing technologies have also attempted to develop some bifunctional catalytic materials that can take into account both OER and HER.

[0004] For example, the patent document with publication number CN109453811A discloses a bifunctional composite water electrolysis catalyst, which is preliminarily prepared by hydrothermal reaction to prepare RuCo-MOF, and then carbonized to prepare RuCo@NC. The patent document with publication number CN113755882A discloses a bimetallic nanoparticle for water electrolysis and its preparation method, specifically recording a preparation method of carbon-coating FeCo bimetallic organic framework compound to prepare MOF / PDA, followed by ammonia annealing and carbonization. The patent document with publication number CN114574899A discloses a bifunctional electrocatalyst for water electrolysis, specifically recording a FeCoMOF / BP composite material bifunctional water electrolysis catalyst. The patent document with publication number CN114921796A discloses a bifunctional self-supporting water electrolysis catalytic material, which is synthesized by introducing a trace amount of chromium doping into the iron-based MOF by a step-by-step hydrothermal method to synthesize a low-content ruthenium-loaded chromium-doped iron-based MOF self-supporting catalytic material (Ru@CrFe-NF).

[0005] In summary, the existing technology discloses some ideas for preparing electrocatalytic materials based on MOF materials, but the active components and active sites of the bifunctional materials prepared by the existing process are unevenly distributed, and the electrocatalytic activity and stability still need to be further improved. Summary of the Invention

[0006] In response to the problems existing in existing HER and OER dual-functional materials, the first purpose of the present invention is to provide a method for preparing a dual-functional electrocatalytic water splitting material, aiming to prepare a material with excellent HER and OER dual performance.

[0007] The second purpose of the present invention is to provide a bifunctional electrocatalytic water splitting material prepared by the preparation method.

[0008] The third object of the present invention is to provide the application of the bifunctional electrocatalytic water splitting material for water electrocatalysis.

[0009] A method for preparing a bifunctional electrocatalytic water splitting material comprises subjecting a first MOF precursor material to a first coordination reaction in a solution containing an additive a and an additive b to obtain a first MOF;

[0010] Using the first MOF as a substrate, a second MOF precursor material is subjected to a second coordination reaction in a solution of an additive c, and the second MOF is deposited on the first MOF to obtain a core-shell dual MOF material; the core-shell dual MOF material is heat-treated to obtain a heat-treated material; the heat-treated material is then mixed with a phosphorus source for phosphating and calcining, and the phosphating product is placed in a liquid cooling medium while hot for rapid cooling to obtain the bifunctional electrocatalytic water splitting material;

[0011] The first MOF precursor material and the second MOF precursor material are raw materials capable of forming MOF, and include a transition metal source and a ligand capable of coordinating with the transition metal source;

[0012] The auxiliary agent a is a surfactant;

[0013] The additive b is a water-soluble compound that can provide at least one of molybdenum, tungsten, niobium, and chromium;

[0014] The auxiliary agent c is a compound of formula 1;

[0015] Formula 1;

[0016] In formula 1, R1 is a mercapto group, a sulfonic acid group or a sulfate group; X is C1~C 10 Saturated carbon chain, C4~C 10 The saturated carbon ring; R2 is H, hydroxyl, amino, carboxyl or ester;

[0017] The liquid cooling medium is a solution containing an additive d, wherein the additive d includes at least one of a water-soluble phosphorus source, an ammonium salt, an organic amine, and a persulfate.

[0018] The present invention innovatively pre-processes a first MOF precursor material under the synergistic action of additives a and b to undergo a first-stage coordination reaction to produce a first MOF material. Subsequently, the first MOF material is used as a substrate, and a second-stage coordination reaction is carried out with the assistance of additive c. The second MOF is coated on the first MOF to produce a core-shell dual-coated MOF material. The core-shell dual MOF is further subjected to heat treatment, phosphating treatment, and rapid cooling treatment in a system containing additive d. This allows the construction of rich defects and dual electrocatalytic active sites in the material, changes the distribution of active sites, and improves the stability of the material interface structure. The bifunctional electrocatalytic water splitting material obtained by the preparation method of the present invention has excellent HER and OER dual catalytic activity.

[0019] In the present invention, the transition metal source is a water-soluble salt of a transition metal, wherein the transition metal comprises at least one of iron, zinc, manganese, cobalt, nickel, titanium, and vanadium; preferably, two or more of these elements. Further preferably, the transition metal elements include at least Zn and optionally at least one of titanium, nickel, iron, and cobalt. Studies have shown that using a composite transition metal source containing zinc can further optimize the distribution uniformity of active centers based on the process of the present invention, thereby further optimizing the HER and OER performance of the prepared material under alkaline conditions.

[0020] The ligand includes at least one of dimethylimidazole, 2-aminoimidazole, terephthalic acid, 2,5-pyridinedicarboxylic acid, 2-(diphenylphosphine)terephthalic acid, and N-oxidized pyridinecarboxylic acid.

[0021] In the present invention, the ratio of the transition metal source to the ligand can be reasonably controlled based on conventional MOF assembly principles. For example, the molar ratio of the ligand to the transition metal source in the first MOF precursor material can be 1 to 50:1; further, 5 to 20:1; and even further, 10 to 15:1.

[0022] In the present invention, the transition metal source, ligand, additive a, and additive b are dispersed in a solvent and subjected to a first-stage coordination reaction. The solvent may be, for example, water or a water-organic solvent mixture. The organic solvent may be, for example, a water-soluble organic component such as a C1-C4 alcohol or acetone. Alternatively, the solvent may be an alcohol-water mixture in a volume ratio of 1:0.5-2.

[0023] The present invention innovatively carries out the first-stage MOF synthesis reaction with the assistance of additives a and b, thereby optimizing the physicochemical structure and surface of the first MOF, which serves as the substrate for the second-stage coordination reaction. This is beneficial for inducing the second MOF to form a high-interface stability composite with the first MOF, and synergizing with subsequent processes to construct and homogenize the distribution of active centers, thereby optimizing the OER and HER performance of the prepared material under alkaline conditions.

[0024] In the present invention, auxiliary agent a comprises at least one of a cationic surfactant, an anionic surfactant, and a neutral surfactant. The cationic surfactant is, for example, a quaternary ammonium salt having one or two (long) carbon chains of 6 to 14 carbon atoms. Furthermore, the remaining carbon chains in the quaternary ammonium salt are short-chain alkyl groups of C1 to C3. The anionic surfactant is, for example, at least one of a sulfate ester having a carbon chain of 6 to 14 carbon atoms (e.g., linear), a sulfonate ester having a carbon chain of 6 to 14 carbon atoms (e.g., linear), a benzenesulfonate, and an alkylbenzenesulfonate ester having a carbon chain of 1 to 6 carbon atoms.

[0025] Preferably, the auxiliary agent a is an anionic surfactant. Studies in the present invention have shown that the use of anionic surfactants in conjunction with the process of the present invention can achieve a better synergistic effect and better HER and OER dual functional performance.

[0026] In the present invention, the auxiliary agent b includes one or more of molybdenum pentachloride, phosphomolybdic acid, tungsten hexachloride, sodium tungstate, niobium pentachloride, niobium oxalate, chromium chloride, zirconium chloride and the like.

[0027] The weight ratio of the transition metal source, the auxiliary agent a, and the auxiliary agent b in the first MOF precursor material is 1:0.001~0.005:0.002~0.01.

[0028] In the present invention, the temperature and time of the first stage coordination reaction can be adjusted as needed. For example, the temperature can be 15-100° C., further can be 20-40° C., and the time can be, for example, 1-15 h, further can be 6-10 h.

[0029] In the present invention, the first MOF is used as the matrix, and the second stage coordination is carried out with the assistance of the additive c, so that the second MOF can be induced to deposit on the first MOF material and the material interface can be improved, thereby enhancing the HER and OER dual functions of the final material.

[0030] In the present invention, the second MOF precursor material and the first MOF precursor material are selected from the same range, but the specific types can be the same or different.

[0031] In the present invention, the auxiliary agent c assists in the synthesis of the second-stage MOF, which can further facilitate the highly interfacially stable composite of the second-stage MOF on the first MOF, and is conducive to the synergy with the process to construct and homogenize the active sites for water electrolysis, thereby improving its HER and OER performance under alkaline conditions.

[0032] Preferably, the auxiliary agent c comprises at least one of Formula 1A and Formula 1B;

[0033] Formula 1A;

[0034] Formula 1B;

[0035] More preferably, the additive c is a molar ratio of 1:0.5 to 2 of Formula 1A and Formula 1B. Studies in the present invention have shown that the preferred additive c can be further combined with the process to further enhance the HER and OER performance of the prepared material under alkaline conditions.

[0036] The weight ratio of the transition metal source to the auxiliary agent c in the second MOF precursor raw material is 1:0.005-0.05; further, it can be 1:0.005-0.01.

[0037] The weight ratio of the transition metal source in the second MOF precursor material to the transition metal source in the first MOF precursor material is 0.1-2:1; further, it can be 0.5-1:1.

[0038] In the present invention, the molar ratio of the ligand to the transition metal source in the second MOF precursor can also be adjusted as needed, for example, it can be 1-50:1; further can be 5-20:1; further can be 10-15:1.

[0039] In the present invention, the temperature and time of the second stage coordination reaction can be adjusted as needed. For example, the temperature can be 15-100° C., further 50-70° C., and the time can be, for example, 1-15 h, further 4-8 h.

[0040] In the present invention, the core-shell dual MOF material is innovatively pre-heat-treated, followed by a phosphating treatment and a rapid cooling treatment assisted by an additive d. This is beneficial for constructing defect structures and active sites suitable for water electrolysis, and is beneficial for improving its dual HER and OER performance.

[0041] In the present invention, the temperature of the heat treatment is 200-600°C, and can further be 300-550°C.

[0042] In the present invention, the heat treatment process is carried out at atmospheric pressure or negative pressure, preferably negative pressure. Research in the present invention has shown that carrying out the heat treatment under negative pressure can further enhance the synergy between the components, facilitate the construction of active sites and beneficial defects, and help further enhance the dual HER and OER performance.

[0043] In the present invention, the heat treatment time is 1 to 6 hours, and can further be 2 to 4 hours.

[0044] In the present invention, the phosphorus source includes at least one of organic phosphorus and inorganic phosphorus.

[0045] The organic phosphorus can be, for example, C2~C 20Phosphate, organic phosphonic acid, etc.; further, it can be at least one of dimethyl methyl phosphate, vinyl phosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, adenosine triphosphate, hexafluorocyclotriphosphazene, and phytic acid.

[0046] The inorganic phosphorus is, for example, at least one of ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate, sodium hydrogen phosphate, sodium dihydrogen phosphate, and the like.

[0047] Preferably, the phosphorus source is organic phosphorus. Studies have shown that phosphating treatment with the participation of preferred organic phosphorus can further enhance the dual performance of HER and OER.

[0048] In the present invention, the weight ratio of the heat-treated product to the phosphorus source is 1:0.2-2, and can further be 1:0.5-1.

[0049] The temperature of the phosphating roasting is 300-600°C, and can further be 350-550°C;

[0050] The phosphating roasting time is 0.5 to 4 hours, and can further be 2 to 4 hours.

[0051] In the present invention, there is no particular requirement for the atmosphere in the phosphating roasting stage, and it may be, for example, at least one of nitrogen and a rare gas.

[0052] In the present invention, the solvent in the liquid phase cooling medium is water or a mixed solution of water and an organic solvent; the organic solvent is an organic solvent miscible with water.

[0053] The auxiliary agent d includes at least one of water-soluble hypophosphite, phytic acid, cyanamide, thiourea, and ammonium persulfate.

[0054] The concentration of the additive d in the liquid phase cooling medium may be 0.005-2M; further, it may be 0.01-1M.

[0055] During the rapid cooling process, the initial temperature difference between the phosphating product and the liquid cooling medium is above 200°C, and can further be 200-500°C.

[0056] The liquid-to-solid ratio during the rapid cooling process may be above 1 mL / g, and may further be 10 to 50 mL / g.

[0057] The present invention also provides a bifunctional electrocatalytic water decomposition material prepared by the preparation method.

[0058] The preparation method of the present invention can give the prepared material special physical and chemical characteristics, and the material prepared by the preparation method can take into account excellent HER and OER dual catalytic activities.

[0059] The present invention also provides an application of the bifunctional electrocatalytic water splitting material, which is used as a HER catalyst and / or an OER catalyst for electrocatalytic water splitting.

[0060] A further application of the present invention is to use the bifunctional electrocatalytic water splitting material of the present invention as a HER catalyst and / or an OER catalyst for electrolysis of water from an alkaline aqueous solution. The alkaline aqueous solution is, for example, a sodium hydroxide solution having a concentration of 0.5 to 5 M.

[0061] In the present invention, the bifunctional electrocatalytic water splitting material of the present invention can be used as a catalytic active component for electrocatalytic water splitting based on known processes.

[0062] The present invention can be further applied to prepare fuel cells using dual-function electrocatalytic water decomposition materials.

[0063] Beneficial effects

[0064] The present invention innovatively conducts the two-stage coordination reaction with the aid of additives a through c to produce a core-shell dual-coated MOF material. The core-shell dual MOF material is then heat-treated, phosphated, and rapidly cooled in a system containing additive d. This creates abundant defects and dual electrocatalytic active sites within the material, optimizes the distribution of active sites, and improves the stability of the material's interfacial structure. The bifunctional electrocatalytic water splitting material produced by the preparation method of the present invention exhibits excellent dual catalytic activity for both the HER and OER reactions.

[0065] The present invention also shows that the treatment with a composite transition metal containing Zn helps to further improve the HER and OER performance of the prepared catalytic material.

[0066] The study also shows that using anionic surfactants as auxiliary agents a to participate in the first stage coordination reaction can help improve the HER and OER performance of the prepared catalytic materials.

[0067] Using Formula 1A and Formula 1B together as an auxiliary agent c to participate in the second-stage coordination reaction helps to improve the HER and OER performance of the prepared catalytic material.

[0068] In addition, the use of negative pressure for the heat treatment helps to further optimize the overall physicochemical structure of the material and helps to improve the HER and OER performance of the prepared catalytic material. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 This is the SEM image of the electrocatalyst material prepared in step 4 of Example 1.

[0070] Figure 2XRD of the composite MOF precursor prepared in step 2 of Example 1 and the electrocatalyst material prepared in step 4.

[0071] Figure 3 This is the TEM image of the electrocatalyst material prepared in step 4 of Example 1.

[0072] Figure 4 The LSV curves of OER and HER of the electrocatalyst material prepared in step 4 of Example 1 are shown, where (a) is the OER performance diagram and (b) is the HER performance diagram. DETAILED DESCRIPTION

[0073] Example 1

[0074] Step 1: Dissolve the ligand (2-methylimidazole) and a transition metal salt (in this case, the transition metal salt includes Zn and iron sulfates in a molar ratio of 1:1) in a 1:1 methanol-water mixture (the molar ratio of 2-methylimidazole to the transition metal element in the transition metal salt is 10:1, and the concentration of 2-methylimidazole in the solution is 2M). Add structural additive a (SDS, 0.2% by weight of the transition metal salt) and functional additive b (phosphomolybdic acid, 0.5% by weight of the transition metal salt). Stir at 30°C for a first coordination reaction for 8 hours. After the reaction, separate the solid and liquid, and dry the filter cake for later use.

[0075] Step 2: The dried material obtained in the previous step is dispersed in a methanol-water mixed solution (methanol-water volume ratio of 1:1) in which a ligand (2-methylimidazole) is dissolved, and a regulating agent c (Formula 1A, the amount of which is 0.8% by weight of the transition metal salt in this step) is added. Then, a transition metal salt (Zn and nickel sulfates with a molar ratio of 1:1; the molar ratio of the ligand and the transition metal sulfate in step 2 is 10:1; the amount of the transition metal is 50% by weight of the transition metal in step 1) is added. The second coordination reaction is then carried out at 60°C with stirring for 6 hours. After the reaction is completed, the solid-liquid separation is carried out and the filter cake is dried to obtain a composite MOF precursor.

[0076] Step 3: placing the product obtained in step 2 in an atmosphere furnace and performing heat treatment at 350° C. under vacuum for 4 hours;

[0077] Step 4: The product of step 3 and a phosphorus source (dimethyl methyl phosphate, the weight ratio of the product of step 3 and the phosphorus source is 1:1) are then phosphated at 550°C for 2 hours under an Ar atmosphere; then, the product is immersed in a coolant while hot for rapid cooling;

[0078] The cooling liquid is an aqueous solution containing 0.01M phytic acid (the liquid-to-solid ratio can be 10-20mL / g) at a temperature of 10°C;

[0079] Then, the electrocatalyst was obtained by solid-liquid separation, alternating washing with water and ethanol, and drying. Figure 1 , XRD see Figure 2 TEM Figure 3 .

[0080] Preparation of working electrode: Weigh the prepared electrocatalyst powder and mix it with isopropyl alcohol and Nafion (the weight ratio of electrocatalyst powder to Nafion is 9:1) to prepare a mixed slurry. Drop the mixed slurry on the glassy carbon electrode and dry it at room temperature to obtain the working electrode.

[0081] OER test: LSV test was performed in 1 M KOH under the following test conditions: 0 ~ 0.7 V vs. Ag / AgCl, scan rate 5 mV s -1 The rotation speed was 1600 rpm; the stability test was performed using the chronopotentiometry method with a current density of 10 mA cm -2 .

[0082] HER test: LSV test was performed in 1 M KOH under the following test conditions: -0.9 ~ -1.3 V vs. Hg / HgO, scan rate 5 mV s -1 The rotation speed was 1600 rpm; the stability test was performed using the chronopotentiometry method with a current density of 10 mA cm -2 .

[0083] The LSV of OER and HER of the catalyst material of Example 1 is shown in FIG. Figure 4 .

[0084] Example 2

[0085] Compared with Example 1, the only difference is that the types of ligands and transition metals are changed. The experimental groups are:

[0086] A: The transition metal salts in steps 1 and 2 are both single ferric sulfate salts, wherein the total amount of transition metal elements in the transition metal salt and other operations are the same as those in Example 1.

[0087] B: The transition metal salt in step 2 is the same as the transition salt in step 1, both of which are sulfates of Zn and iron in a molar ratio of 1:1; wherein the component ratio, dosage and other operations of the transition metal salt in step 2 are the same as those in Example 1.

[0088] C: The ligands in step 1 and step 2 are both terephthalic acid, wherein the molar ratio of the ligand to the transition metal in the transition metal salt is 15:1.

[0089] The results of Examples 1 and 2 are shown in Table 1:

[0090]

[0091] It can be seen from Examples 1 and 2 that the use of composite transition metals, especially composite transition metals containing Zn, can further enhance the OER and HER performance of the prepared materials.

[0092] Example 3

[0093] Compared with Example 1, the only difference is that the type of auxiliary agent a in step 1 is changed. The experimental groups are:

[0094] Group A: additive a is cationic surfactant CTAB;

[0095] Group B: auxiliary agent a is a non-ionic (neutral) surfactant laureth-7.

[0096] Group C: The additive a is 0.5% by weight of the transition metal salt.

[0097] Other operations and parameters are the same as in Example 1.

[0098] The test results are shown in Table 2:

[0099]

[0100] It can be seen from Examples 1 and 3 that the use of anionic surfactant as auxiliary agent a helps to further strengthen the physicochemical structure of the prepared material and helps to further enhance the OER and HER performance of the prepared material.

[0101] Example 4

[0102] Compared with Example 1, the only difference is that the type of auxiliary agent b in step 1 is changed. The experimental groups are:

[0103] Group A: additive b is sodium tungstate;

[0104] Group B: additive b is niobium oxalate;

[0105] Group C: The additive b is 1% by weight of the transition metal salt.

[0106] Other operations and parameters are the same as in Example 1.

[0107] The test results are shown in Table 3:

[0108]

[0109] It can be seen from Examples 1 and 4 that the use of the additive b is beneficial to enhancing the OER and HER performance of the prepared materials.

[0110] Example 5

[0111] Compared with Example 1, the only difference is that the type of auxiliary agent c in step 2 is changed. The experimental groups are:

[0112] Group A: auxiliary agent c is formula 1B;

[0113] Group B: additive c is a mixed sample of Formula 1A and Formula 1B (the weight ratio of the two is 1:1);

[0114] Group C: The additive c is 4% of the transition metal salt in step 2.

[0115] Other operations and parameters are the same as in Example 1.

[0116] The test results are shown in Table 4:

[0117]

[0118] It can be seen from Examples 1 and 5 that the use of the additive c, especially the additive c of Formula 1A and Formula 1B combined, can further enhance the OER and HER performance of the prepared material.

[0119] Example 6

[0120] Compared with Example 1, the only difference is that the conditions of step 3 are changed. The experimental groups are:

[0121] Group A: heat treatment temperature is 550℃ and time is 2h;

[0122] Group B: The heat treatment process was carried out at normal pressure, in which the atmosphere was Ar.

[0123] Other operations and parameters are the same as in Example 1.

[0124] The test results are shown in Table 5:

[0125]

[0126] It can be seen from Examples 1 and 6 that the negative pressure heat treatment process can further enhance the OER and HER performance of the prepared materials.

[0127] Example 7

[0128] Compared with Example 1, the only difference is that the type and amount of phosphorus source in step 4 are changed. The experimental groups are:

[0129] Group A: the phosphorus source was adenosine triphosphate;

[0130] Group B: phosphorus source is ammonium phosphate;

[0131] Group C: The weight ratio of the product of step 3 and the phosphorus source is 1:0.5;

[0132] Group D: phosphating temperature is 350℃ and time is 4h;

[0133] Other operations and parameters are the same as in Example 1.

[0134] The test results are shown in Table 6:

[0135]

[0136] It can be seen from Examples 1 and 7 that the phosphating process described in the present invention, especially the use of organic phosphorus as a phosphorus source, can effectively enhance the OER and HER performance of the prepared material.

[0137] Example 8

[0138] Compared with Example 1, the only difference is that the type of coolant in step 4 is changed. The experimental groups are:

[0139] Group A: The coolant is 1M thiourea and the solvent is water;

[0140] Group B: The coolant was 0.5 M sodium hypophosphite and the solvent was water;

[0141] Other operations and parameters are the same as in Example 1.

[0142] The test results are shown in Table 7:

[0143]

[0144] It can be seen from Examples 1 and 8 that the functionalized quenching treatment process described in the present invention can effectively enhance the OER and HER performance of the prepared materials.

[0145] Comparative Example 1

[0146] Compared with Example 1, the only difference is that in step 1, no auxiliary agent a and auxiliary agent b are added, and other operations and parameters are the same as in Example 1.

[0147] Comparative Example 2

[0148] Compared with Example 1, the only difference is that in step 1, no auxiliary agent a is added, and other operations and parameters are the same as in Example 1.

[0149] Comparative Example 3

[0150] Compared with Example 1, the only difference is that in step 1, no auxiliary agent b is added, and other operations and parameters are the same as in Example 1.

[0151] Comparative Example 4

[0152] Compared with Example 1, the only difference is that in step 2, no auxiliary agent c is added, and the other operations and parameters are the same as those in Example 1.

[0153] Comparative Example 5

[0154] Compared with Example 1, the only difference is that step 2 is not performed, but the raw materials in step 2, such as ligand, auxiliary agent c and transition metal source, are added together in step 1. Other operations and parameters are the same as those in Example 1.

[0155] Comparative Example 6

[0156] Compared with Example 1, the only difference is that step 3 is not performed, and the product of step 2 is directly processed by step 4. Other operations and parameters are the same as those in Example 1.

[0157] Comparative Example 7

[0158] Compared with Example 1, the only difference is that in step 4, the phosphating is followed by furnace cooling, and the other operations and parameters are the same as those in Example 1.

[0159] Comparative Example 8

[0160] Compared with Example 1, the only difference is that in step 4, no additive d is added to the coolant, and other operations and parameters are the same as in Example 1.

[0161] Comparative Example 9

[0162] Compared with Example 1, the only difference is that no auxiliary agent b is added in step 1, and no auxiliary agent c is added in step 2. Instead, auxiliary agent b and auxiliary agent c are mixed with the phosphorus source in step 3 for phosphating. Other operations and parameters are the same as those in Example 1.

[0163] The test results of each comparative example are shown in Table 8:

[0164]

[0165] As shown in Example 1 and Comparative Example 1, the innovative two-stage coordination reaction with the assistance of additives a to c produces a core-shell dual-coated MOF material. The core-shell dual MOF material is then heat-treated, phosphated, and rapidly cooled in a system containing additive d. This allows for the construction of rich defects and dual electrocatalytic active sites in the material, while also improving the stability of the material's interface structure. The bifunctional electrocatalytic water splitting material produced by the preparation method of the present invention exhibits excellent HER and OER dual catalytic activity.

Claims

1. A method for preparing a bifunctional electrocatalytic water splitting material, characterized in that: Performing a first coordination reaction on a first MOF precursor material in a solution containing an additive a and an additive b to obtain a first MOF; Using the first MOF as a substrate, a second MOF precursor material is subjected to a second coordination reaction in a solution of an additive c, and the second MOF is deposited on the first MOF to obtain a core-shell dual MOF material; the core-shell dual MOF material is heat-treated to obtain a heat-treated material; the heat-treated material is then mixed with a phosphorus source for phosphating and calcining, and the phosphating product is placed in a liquid cooling medium while hot for rapid cooling to obtain the bifunctional electrocatalytic water splitting material; The first MOF precursor material and the second MOF precursor material are raw materials capable of forming MOF, and include a transition metal source and a ligand capable of coordinating with the transition metal source; Auxiliary agent a is a surfactant; The additive b is a water-soluble compound that can provide at least one of molybdenum, tungsten, niobium, and chromium; The auxiliary agent c is a compound of formula 1; Formula 1; In formula 1, R1 is a thiol, sulfonic acid or sulfate group; X is C1~C 10 Saturated carbon chain, C4~C 10 A saturated carbon ring; R2 is H, hydroxyl, amino, carboxyl or ester; The liquid cooling medium is a solution containing an additive d, wherein the additive d includes at least one of a water-soluble phosphorus source, an ammonium salt, an organic amine, and a persulfate.

2. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The transition metal source is a water-soluble salt of a transition metal, wherein the transition metal comprises at least one element selected from the group consisting of iron, zinc, manganese, cobalt, nickel, titanium, and vanadium; The ligand comprises at least one of dimethylimidazole, 2-aminoimidazole, terephthalic acid, 2,5-pyridinedicarboxylic acid, 2-(diphenylphosphine)terephthalic acid, and N-pyridinecarboxylic acid oxide; The molar ratio of the ligand to the transition metal source can be 1 to 50:

1.

3. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The auxiliary agent a includes at least one of a cationic surfactant, an anionic surfactant, and a neutral surfactant; The additive b includes one or more of molybdenum pentachloride, phosphomolybdic acid, tungsten hexachloride, sodium tungstate, niobium pentachloride, niobium oxalate, chromium chloride, and zirconium chloride; The weight ratio of the transition metal source, the auxiliary agent a, and the auxiliary agent b in the first MOF precursor material is 1:0.001~0.005:0.002~0.

01.

4. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The auxiliary agent c comprises at least one of Formula 1A and Formula 1B; Formula 1A; Formula 1B; The weight ratio of the transition metal source and the additive c in the second MOF precursor raw material is 1:0.005~0.05; The weight ratio of the transition metal source in the second MOF precursor material to the transition metal source in the first MOF precursor material is 0.1-2:

1.

5. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The temperature of heat treatment is 200~600℃; Heat treatment is carried out under negative pressure; The heat treatment time is 1~6h.

6. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The phosphorus source includes at least one of organic phosphorus and inorganic phosphorus; The weight ratio of the heat-treated product to the phosphorus source is 1:0.2~2; The temperature of phosphating roasting is 300~600℃; The phosphating roasting time is 0.5~4h.

7. The method for preparing the bifunctional electrocatalytic water splitting material according to claim 1, wherein: The solvent in the liquid cooling medium is water or a mixed solution of water and an organic solvent; the organic solvent is an organic solvent miscible with water; The additive d comprises at least one of water-soluble hypophosphite, phytic acid, cyanamide, thiourea, and ammonium persulfate; During the rapid cooling process, the initial temperature difference between the phosphating product and the liquid cooling medium is above 200°C.

8. A bifunctional electrocatalytic water splitting material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of a bifunctional electrocatalytic water splitting material prepared by the preparation method according to any one of claims 1 to 7, characterized in that: It can be used as HER catalyst and / or OER catalyst for electrocatalytic water splitting.

10. The use according to claim 9, characterized in that It is used to prepare fuel cells.

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