A rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater

Abstract

The application discloses a kind of for electrolysis seawater hydrogen preparation sulphate intercalation catalyst's quick synthesis method, the method is as follows: one, metal salt is dissolved in solvent, obtain initial deposition liquid, stabilizer is dissolved in initial deposition liquid, obtain electrodeposition liquid;Two, substrate is placed in electrodeposition liquid, and CoFe catalyst precursor is obtained by electrodeposition;Three, CoFe catalyst precursor is placed in the mixed solution of thiourea and potassium hydroxide and is oxidized;Four, after oxidation catalyst is placed in potassium hydroxide solution and is cyclically oxidized.The preparation method of the application is simple, fast, efficient, and can be applied to the preparation of large-area electrode, and the activated electrode has superior OER activity and strong chlorine resistance, and the current density reaches 100mA·cm ‑2 Only 265mV overpotential is required, and only a low decay rate of 5.0 μV / h occurs after continuous electrolysis in natural seawater for 1000h.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-salinity water hydrogen energy catalysis, and relates to a preparation method of a non-noble metal catalyst, in particular to a rapid preparation method of a high-efficiency stable sulfate intercalation catalyst for hydrogen production by electrolyzing seawater. BACKGROUND

[0002] The increasing global concern about serious environmental problems and energy crisis has driven the development of renewable clean energy, especially hydrogen energy, solar energy and wind energy. Among them, hydrogen energy is considered as a superior alternative to traditional fuels due to its unique pollution-free, high energy density and wide sources. Hydrogen energy can be obtained through coal and biomass pyrolysis, natural gas reforming and water electrolysis, etc., among which water electrolysis is considered as the most efficient and cleanest method for hydrogen production. However, water electrolysis requires a large amount of pure water. Combined with the increasing energy demand, the future consumption of water for water electrolysis will further increase, exacerbating the "water crisis" on earth. Seawater accounts for about 97% of water resources on earth, and using seawater for hydrogen production by electrolysis can directly alleviate the water resource competition between life and hydrogen production industry.

[0003] The water electrolysis reaction is composed of two half-reactions, the oxygen evolution reaction (OER) occurs at the anode, and the hydrogen evolution reaction (HER) occurs at the cathode, in which the anode energy consumption accounts for more than 90% of the energy consumption of water electrolysis reaction. However, the impurity ion Cl - is also easily oxidized at the anode, and chlorine evolution reaction (CER) occurs, which not only causes the increase of anode energy consumption, but also leads to the corrosion of the anode. Although there is a theoretical potential difference of 0.48V between CER and OER. However, due to the poor OER activity of the actual catalyst, the potential difference between OER and CER is further shortened, which limits its stable hydrogen production at high current.

[0004] CN117468043A discloses a single-atom Ir supported on a NiFe LDH type catalyst, and the dispersed Ir provides more catalytic active sites, which significantly improves the OER activity. However, the catalyst contains noble metal Ir, which leads to high cost of the catalyst, so it is difficult to realize industrial application. CN117385405A discloses a method for compactly coating NF surface with NiFe LDH, which avoids direct contact between NF skeleton and Cl - , and further inhibits Cl corrosion. However, its stability can only be maintained at 400mA·cm -2The current density of 250h far fails to meet the requirement of electrode stability for industrial water electrolysis. CN117187855A discloses a synthesis method of a fast surface reconstruction NiFe LDH, which is synthesized by hydrothermal method, boron modification and cyclic voltammetry CV-B-NiFe LDH. The material realizes electrolysis in natural seawater to reach a current density of 100mA·cm -2 Only 219mV overpotential is needed, and excellent reaction kinetics (53.5mV·dec -1 ) is exhibited. However, the synthesis method is complex and needs to introduce additional boron, which makes the method not suitable for the synthesis of large-area electrodes.

[0005] The currently disclosed non-noble metal catalysts all have obvious problems of high cost, poor corrosion resistance and high difficulty in industrial application, and are difficult to be directly applied to seawater electrolysis. Therefore, it is crucial to develop a new type of catalyst to realize high OER catalytic activity, high selectivity and strong corrosion resistance for seawater direct electrolysis. SUMMARY

[0006] The purpose of the present application is to provide a fast synthesis method of a sulfate intercalation catalyst for electrolysis of seawater to produce hydrogen, which grows CoFe on the surface of the substrate by electrodeposition-oxidation method and further oxidizes to form a CoFe LDH structure with sulfate intercalation, so as to obtain a high-performance seawater direct electrolysis oxygen evolution catalyst with a specific structure, and uses the sulfate in the interlayer to regulate the catalytic activity of CoFe LDH and inhibit the dissolution of Co 3+ The preparation method of the present application is simple, fast and efficient, and can be applied to the preparation of large-area electrodes. The activated electrode has excellent OER activity and strong chlorine resistance, and only needs 265mV overpotential to reach a current density of 100mA·cm -2 in natural seawater, and only a low decay rate of 5.0uV / h occurs after continuous electrolysis in natural seawater for 1000h. At the same time, the catalyst has the advantages of low synthesis cost, high stability and good catalytic activity, and provides a new material research idea for seawater electrolysis to produce hydrogen.

[0007] The purpose of the present application is realized by the following technical solutions:

[0008] A fast synthesis method of a sulfate intercalation catalyst for electrolysis of seawater to produce hydrogen, specifically comprising the following steps:

[0009] Step one, dissolving metal salt in solvent to obtain initial deposition solution, then slowly dissolving stabilizer in the initial deposition solution to obtain electrodeposition solution, wherein:

[0010] The metal salt is cobalt salt and iron salt;

[0011] The cobalt salt is one of cobalt chloride, cobalt sulfate or cobalt nitrate, with a concentration of 0.15-0.25 mol / L, such as 0.15 mol / L, 0.18 mol / L, 0.20 mol / L, 0.23 mol / L and 0.25 mol / L, but not limited to the listed concentrations, other concentrations not listed in the concentration range are also applicable;

[0012] The iron salt is one of ferrous chloride or ferrous sulfate, with a concentration of 0.03-0.08 mol / L, such as 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L and 0.08 mol / L, but not limited to the listed concentrations, other concentrations not listed in the concentration range are also applicable;

[0013] The solvent is deionized water;

[0014] The stabilizer is one or more of any combination of ammonium chloride, boric acid and sodium citrate, typical but not limited to the combination includes the combination of boric acid and ammonium chloride, the combination of ammonium chloride and sodium citrate;

[0015] The concentration of the stabilizer is 0.2-0.5 mol / L, such as 0.20 mol / L, 0.30 mol / L, 0.40 mol / L, 0.50 mol / L, but not limited to the listed concentrations, other concentrations not listed in the concentration range are also applicable;

[0016] Step two, the substrate is placed in the electrodeposition solution for electrodeposition, then washing and drying to remove surface residual ions, to obtain CoFe catalyst precursor, wherein:

[0017] The substrate is one of foamed nickel and Raney nickel mesh;

[0018] The electrodeposition time is 10-20 min, the deposition current is 60 mA / cm 2 Pulse current, temperature is 40-60℃, such as 40℃, 45℃, 50℃, 55℃ and 60℃, but not limited to the listed temperatures, other temperatures not listed in the concentration range are also applicable;

[0019] The reagent used for washing should include one or both of anhydrous ethanol and deionized water, but at least contains deionized water, and the drying method is vacuum drying or freeze drying;

[0020] Step three, the CoFe catalyst precursor is placed in a mixed solution of thiourea and potassium hydroxide for oxidation, wherein:

[0021] The concentration of potassium hydroxide in the mixed solution of thiourea and potassium hydroxide is 1.0 mol / L, and the concentration of thiourea is 0.03-0.05 mol / L, for example, the concentration of thiourea can be 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, but not limited to the listed concentrations, other concentrations not listed in this range are also applicable;

[0022] The solvent in the mixed solution of thiourea and potassium hydroxide is deionized water;

[0023] The current intensity of the oxidation is 200-250 mA·cm -2 , but not limited to the listed current density, other current densities not listed in this range are also applicable;

[0024] The oxidation time is 3-5 min, but not limited to the listed oxidation time, other oxidation times not listed in this range are also applicable;

[0025] Step four, the oxidized catalyst is placed in a potassium hydroxide solution for cyclic oxidation to obtain a sulfate intercalated catalyst, wherein:

[0026] The concentration of the potassium hydroxide solution is 1.0 mol / L;

[0027] The solvent in the potassium hydroxide solution is deionized water;

[0028] The potential interval of the cyclic oxidation is 0.2-0.7 V, and the rate is 5 mV·s -1 ;

[0029] The number of cyclic oxidations is 40-50 times, for example, it can be 40 times, 45 times, 50 times, but not limited to the listed oxidation times, other oxidation times not listed in this range are also applicable.

[0030] The catalyst prepared by the above method can be used for direct electrolysis of seawater to produce hydrogen, and the catalyst surface is uniformly distributed with cobalt, iron and sulfur elements. The oxygen evolution reaction (OER) is a typical four-electron reaction, which undergoes OH - →OH * →O * →OOH * →O2, the theoretical potential is 1.23 V. However, due to the strong or weak adsorption of the reaction intermediates, the actual OER potential is often higher than 1.23 V. The unfilled d orbitals of cobalt make it have a better adsorption strength for reaction intermediates, so it shows strong catalytic activity. In addition, studies have shown that Fe doping can effectively regulate the adsorption strength, and NiFe LDH has been proven to be the most effective OER catalyst, with much better catalytic activity than commercial RuO2. Secondly, anions can effectively regulate the catalytic activity of LDH, especially SO42- and PO4 3- . Therefore, the present application deposits cobalt and iron to form CoFe, and further deposits SO4 2- and CoFe LDH to form sulfate intercalated CoFe LDH, thereby constructing a high-efficiency and stable direct electrolysis seawater hydrogen production catalyst.

[0031] Compared with the prior art, the present application has the following advantages:

[0032] 1. The preparation method of the catalyst is simple in process, low in operation difficulty, low in equipment requirement, and easy to prepare large-area electrodes.

[0033] 2. In the preparation process, CoFe LDH and SO4 2- are activated synchronously by electrodeposition and oxidation, and a specific intercalated structure (SO4 2- / CoFe LDH) is formed.

[0034] 3. The synthesized SO4 2- / CoFe LDH has a clear nanosheet structure, and SAED diffraction proves that SO4 2- is inserted into the interlayer of CoFe LDH and increases the interlayer spacing. Experimental results prove that the catalyst of the present application has a low required voltage and excellent catalytic activity in the process of direct electrolysis seawater hydrogen production. In natural seawater, a current density of 100 mA·cm -2 requires only an overpotential of 265 mV, and the catalyst has a decay rate of only 5 muV / h under an industrial-level current of 500 mA·cm -2 for 1000h.

[0035] 4. The materials required for synthesizing the catalyst in the present application are cheap and easy to obtain, and the catalyst has the advantages of low preparation cost, low electrolysis energy consumption, and high stability, and has a wide application prospect in the fields of marine wind power consumption green hydrogen production and high-salinity wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is the SEM graph of the catalyst in Example 1;

[0037] Figure 2 is the TEM graph of the catalyst in Example 1;

[0038] Figure 3 is the LSV curve of the catalyst in Example 1;

[0039] Figure 4 is the full hydrolysis performance LSV curve of the catalyst in Example 1;

[0040] Figure 5Voltage curve for constant current for direct electrolysis of seawater in Example 1;

[0041] Figure 6 TEM image of catalyst after stability test in Example 1;

[0042] Figure 7 LSV curve of catalyst before and after stability test in Example 1;

[0043] Figure 8 LSV curve of catalyst before and after stability test in Example 1;

[0044] Figure 9 LSV curve of catalyst in Example 2;

[0045] Figure 10 LSV curve of catalyst in Example 3. DETAILED DESCRIPTION

[0046] The technical solutions of the present application are further described below in conjunction with examples, but are not limited thereto, and any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the technical solutions of the present application shall be encompassed in the protection scope of the present application.

[0047] Example 1

[0048] The sulfate intercalation catalyst is prepared according to the following steps in this example:

[0049] Step one, CoSO4 and FeSO4 are dissolved in deionized water to obtain an initial deposition solution, and then ammonium chloride and boric acid are slowly dissolved in the initial deposition solution to obtain an electrodeposition solution. Among them: the electrodeposition solution includes 0.15 mol / L CoCl2, 0.03 mol / L FeSO4, 0.2 mol / L NH4Cl and 0.2 mol / L H3BO3.

[0050] Step two, the foamed nickel is immersed in the electrodeposition solution, and deposition is carried out at a current density of 60 mA·cm -2 for 10 min.

[0051] Step three, anhydrous ethanol and deionized water are used for cleaning respectively, and the catalyst precursor is obtained by vacuum drying.

[0052] Step four, the catalyst precursor is oxidized in a 0.03 mol / L thiourea and 1.0 mol / L potassium hydroxide solution at a current of 200 mA·cm -2 for 3 min.

[0053] Step five, the oxidized catalyst is oxidized in a 1.0 mol / L potassium hydroxide solution at an oxidation potential interval of 0.2-0.7 V at a rate of 5 mV·s-1 The catalyst was obtained by 40 times of rate cycle oxidation.

[0054] The catalyst was characterized by SEM and TEM, and the results are shown in Figure 1 and Figure 2 It can be seen from Figure 1 that the catalyst surface grows nanosheet structure; it can be seen from Figure 2 that SO4 2- is successfully inserted into the interlayer of CoFe LDH to form an intercalation structure.

[0055] The catalyst was tested for OER performance, and the test method was as follows: the electrolyte containing real seawater and 1.0 mol / L KOH was poured into a single-chamber electrolysis tank, and the test was carried out under a three-electrode system, the working electrode was the catalyst prepared in the embodiment, the counter electrode was a platinum sheet, and the reference electrode was Hg / HgO. The performance of the catalyst was evaluated by linear sweep voltammetry, and the test results are shown in Figure 3 It can be seen from Figure 3 that when the current density reaches 100 mA·cm -2 , the overpotential is only 265 mV.

[0056] The catalyst was tested for overall water splitting performance, and the test method was as follows: Pt / C / NF electrode was used as the counter electrode, and the catalyst prepared in the embodiment was used as the working electrode, and the performance of the catalyst system was evaluated by linear sweep voltammetry, and the test results are shown in Figure 4 The preparation method of the Pt / C / NF electrode was as follows: 30 mg of Pt / C was dissolved in a mixed solvent composed of 30 μL and 200 μL, and after ultrasonic mixing for 30 min, it was coated on the cleaned nickel foam, and finally vacuum dried at 60°C for 30 min. It can be seen from Figure 4 that when the current density reaches 100 mA·cm -2 , the voltage is only 1.682 V.

[0057] The catalyst was tested for stability, and the test method was as follows: seawater containing 1 mol / L of potassium hydroxide was poured into a single-chamber electrolysis tank, and the catalyst prepared in the embodiment was used as the working electrode, and Pt / C / NF was used as the counter electrode, and electrolysis was carried out under a constant current of 500 mA·cm -2 , and the obtained electrolysis tank voltage data are shown in Figure 5 After the test, the catalyst was characterized by SEM, and the results are shown in Figure 6 The Faraday efficiency of the electrode is shown in Figure 7 , and the OER performance of the catalyst before and after 1000 h test is shown in Figure 8 It can be seen from Figures 5 to 8 that SO4 2-The / CoFe LDH can realize stable seawater electrolysis for 1000h, and almost 100% OER selectivity can be realized in the electrolysis process. The nanosheet structure on the electrode surface is maintained after 1000h of testing, and the performance decay rate is less than 5μV / h.

[0058] Example 2

[0059] The sulfate intercalation catalyst is prepared according to the following steps:

[0060] Step one, CoCl2 and FeCl2 are dissolved in deionized water to obtain an initial deposition solution, and then ammonium chloride and sodium citrate are slowly dissolved in the initial deposition solution to obtain an electrodeposition solution. Among them: the electrodeposition solution includes 0.15mol / L CoCl2, 0.03mol / L FeSO4, 0.5mol / L NH4Cl and 0.5mol / L sodium citrate.

[0061] Step two, immerse the Raney nickel mesh in the electrodeposition solution, and deposit for 20min at a current density of 60mA·cm -2 .

[0062] Step three, clean with anhydrous ethanol and deionized water respectively, and obtain the catalyst precursor by freeze-drying.

[0063] Step four, oxidize the catalyst precursor in a 0.05mol / L thiourea and 1.0mol / L potassium hydroxide solution at a current of 250mA·cm -2 for 5min.

[0064] Step five, cycle the oxidized catalyst in a 1.0mol / L potassium hydroxide solution at an oxidation potential of 0.2-0.7V at a rate of 5mV·s -1 for 50 times to obtain the catalyst.

[0065] The OER performance test is conducted on the catalyst prepared in this example, and the test results are shown in Figure 9 . As can be seen from Figure 9 , when the current density reaches 100mA·cm -2 , the overpotential is only 274mV.

[0066] Example 3

[0067] The sulfate intercalation catalyst is prepared according to the following steps:

[0068] Step one, Co(NO3)2 and FeCl2 were dissolved in deionized water to obtain an initial deposition solution, and then ammonium chloride and sodium citrate were slowly dissolved in the initial deposition solution to obtain an electrodeposition solution. Among them: the electrodeposition solution includes 0.20 mol / L Co(NO3)2, 0.04 mol / L FeSO4, 0.4 mol / L NH4Cl and 0.4 mol / L sodium citrate.

[0069] Step two, the foamed nickel was immersed in the electrodeposition solution, and the deposition was carried out at a current density of 60 mA·cm -2 for 15 min.

[0070] Step three, deionized water and deionized water were used for cleaning respectively, and the catalyst precursor was obtained by freeze-drying.

[0071] Step four, the catalyst precursor was oxidized in 0.04 mol / L thiourea and 1.0 mol / L potassium hydroxide solution at a current of 230 mA·cm -2 for 4 min.

[0072] Step five, the oxidized catalyst was cyclically oxidized in 1.0 mol / L potassium hydroxide solution at an oxidation potential interval of 0.2-0.7 V at a rate of 5 mV·s -1 for 45 times to obtain the catalyst.

[0073] The catalyst prepared in this embodiment was tested for OER performance, and the test results are shown in Figure 10 . It can be seen from Figure 10 that when the current density reaches 100 mA·cm -2 , the overpotential is only 268 mV.

Claims

1. A rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater, characterized in that The method comprises the following steps: Step 1: dissolving a metal salt in a solvent to obtain an initial deposition solution, and then slowly dissolving a stabilizer in the initial deposition solution to obtain an electrodeposition solution, wherein: the metal salt is a cobalt salt and an iron salt, the concentration of the cobalt salt is 0.15-0.25 mol / L, and the concentration of the iron salt is 0.03-0.08 mol / L; the concentration of the stabilizer is 0.2-0.5 mol / L; the iron salt is one of ferrous chloride and ferrous sulfate, and the stabilizer is one of a combination of boric acid and ammonium chloride, or a combination of ammonium chloride and sodium citrate; Step 2: Place the substrate in an electroplating solution for electroplating, then wash and dry to obtain a CoFe catalyst precursor, wherein: the electroplating time is 10-20 min, the deposition current is 60 mA / cm 2 Pulse current, temperature is 40~60℃; Step 3: Place the CoFe catalyst precursor in a mixed solution of thiourea and potassium hydroxide for oxidation, wherein the oxidation current intensity is 200-250 mA·cm -2 , time is 3~5 min; Step 4: placing the oxidized catalyst in a potassium hydroxide solution for cyclic oxidation to obtain a sulfate intercalation catalyst, wherein: the potential range of the cyclic oxidation is 0.2-0.7 V, and the rate is 5 mV·s -1 , 40 to 50 times.

2. The rapid synthesis method of sulfate intercalation catalyst for electrolysis of seawater to produce hydrogen according to claim 1, characterized in that In the step 1, the cobalt salt is one of cobalt chloride, cobalt sulfate or cobalt nitrate, and the solvent is deionized water.

3. The rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater according to claim 1, characterized in that In the step 2, the substrate is one of foam nickel and Raney nickel mesh.

4. The rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater according to claim 1, characterized in that In the step 2, the reagents used for washing include one or both of anhydrous ethanol and deionized water, and the drying method is vacuum drying or freeze drying.

5. The rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater according to claim 1, characterized in that In the step 3, in the mixed solution of thiourea and potassium hydroxide, the concentration of potassium hydroxide is 1.0 mol / L, the concentration of thiourea is 0.03-0.05 mol / L, and the solvent is deionized water.

6. The rapid synthesis method of sulfate intercalation catalyst for hydrogen production by electrolysis of seawater according to claim 1, characterized in that In the step 4, the concentration of the potassium hydroxide solution is 1.0 mol / L, and the solvent is deionized water.

7. A sulfate intercalation catalyst synthesized by the method according to any one of claims 1 to 6.

8. Use of a sulfate intercalation catalyst synthesized by the method according to any one of claims 1 to 6 in direct electrolysis of seawater to produce hydrogen.

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