A chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel catalyst, a preparation method and application thereof

Abstract

The application provides a chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel catalyst and a preparation method and application thereof. The method comprises the following steps: dissolving Fe(NO3)3*9H2O and Cr(NO3)3*9H2O in deionized water to obtain a mixed solution; immersing foam nickel into the mixed solution, and then adding Na2S2O3 to react, so that chromium-sulfur double-doped nickel-iron layered double hydroxide is in-situ grown on the surface of the foam nickel to obtain a mixture; and washing and drying the mixture to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel catalyst. When the catalyst is used for electrolysis of water to produce hydrogen, the electrolyte is a mixed solution of glucose and KOH, the synthesis time of the catalyst is greatly shortened, the applied potential required for electrolysis of water is reduced, and the efficiency of electrolysis of water to prepare high-purity hydrogen is improved.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic hydrogen and oxygen production, specifically relating to a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, its preparation method, and its application. Background Technology

[0002] Electrolysis of water to produce high-purity hydrogen is the most environmentally friendly method for hydrogen production to date, enabling clean production and sustainable supply, and effectively addressing the energy crisis and environmental issues. However, water electrolysis involves two half-reactions: oxygen evolution at the anode (OER) and hydrogen evolution at the cathode (HER). These reactions have significant overpotentials, requiring a large additional potential to be applied in practical applications, severely limiting the large-scale application of this technology.

[0003] Currently, platinum (Pt) and ruthenium oxide (RuO2) and iridium oxide (IrO2) are used as highly efficient catalysts for HER and OER, respectively. However, these excellent catalysts are expensive and have low reserves, limiting their commercial application. Therefore, developing low-cost, highly active non-precious metal catalysts is a key technical challenge to promote the development of water electrolysis.

[0004] Currently, there are numerous reports on the use of advanced transition metal-based catalysts, such as transition metal oxides, hydroxides, phosphides, and sulfides, to replace traditional noble metal catalysts in the efficient electrolysis of water. Among these, layered double hydroxides (LDHs) have emerged as a promising class of bifunctional catalysts in alkaline media due to their large specific surface area, tunable composition, and excellent electrochemical properties. However, current methods for the direct synthesis of LDH include co-precipitation and sol-gel methods, while indirect methods include calcination and ion exchange. Currently, nickel-iron layered double hydroxides are widely used. The morphologies of nickel-iron layered double hydroxides prepared by hydrothermal methods and co-precipitation include lamellar and plate-like structures. However, the preparation of nickel-iron layered double hydroxides using these methods often requires a long time, and their catalytic performance needs further improvement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, its preparation method, and its application. This significantly shortens the catalyst synthesis time, reduces the external potential required for water electrolysis, and improves the efficiency of producing high-purity hydrogen through water electrolysis.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst includes the following steps:

[0008] S1, Fe(NO3)3·9H2O and Cr(NO3)3·9H2O are dissolved in deionized water at a mass ratio of (3.5~4.5):(0.05~0.5) to obtain a mixed solution;

[0009] S2, the nickel foam is immersed in the mixture, and then Na2S2O3 is added to react. The mass ratio of Na2S2O3 to Fe(NO3)3·9H2O in S1 is (0.5~1.5):(3.5~4.5). Chromium-sulfur double-doped nickel-iron layered double hydroxide is grown in situ on the surface of the nickel foam to obtain a mixture.

[0010] S3. After washing and drying the mixture, a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst is obtained.

[0011] Preferably, the nickel foam described in S2 is obtained by the following process:

[0012] The nickel foam to be treated is immersed in acetone and ultrasonically cleaned for 10-20 minutes to obtain pre-cleaned nickel foam. Then, the pre-cleaned nickel foam is immersed in 2-4 mol / L hydrochloric acid and ultrasonically cleaned for 10-20 minutes. After that, it is rinsed alternately with anhydrous ethanol and deionized water 2-5 times. Finally, it is vacuum dried at 20-35°C for 8-12 hours to obtain the nickel foam.

[0013] Preferably, the ratio of deionized water to Fe(NO3)3·9H2O in S1 is 100mL:(3.5~4.5)g.

[0014] Preferably, in step S1, Fe(NO3)3·9H2O and Cr(NO3)3·9H2O are added to deionized water and stirred magnetically for 5–20 min to obtain a mixed solution.

[0015] Preferably, in S2, the reaction is carried out at room temperature.

[0016] Furthermore, in S2, the reaction proceeds for 2 to 10 minutes.

[0017] Preferably, in step S3, the mixture in the reaction solution is washed 2 to 6 times with anhydrous ethanol and deionized water respectively, and then dried.

[0018] Preferably, in step S3, the washed mixture is vacuum dried at room temperature for 8–15 hours.

[0019] The chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst obtained by the preparation method of any one of the above-described methods.

[0020] The application of chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst in hydrogen evolution by water electrolysis, wherein the electrolyte of the double hydroxide / foam nickel catalyst during hydrogen evolution by water electrolysis is a mixed solution of glucose and KOH, wherein the concentration of KOH is 0.5-1.5M and the concentration of glucose is 20-40mM.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects:

[0022] This invention discloses a method for preparing a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foamed nickel catalyst. First, Fe(NO3)3·9H2O and Cr(NO3)3·9H2O are dissolved in deionized water to obtain a mixed solution. Then, nickel foam is immersed in the mixed solution. Finally, Na2S2O3 is added to initiate the reaction. The reaction is carried out using a standard electrode potential Eq(Fe... 3+ / Fe 2+ )>Eq(Ni 2+ / Ni 0 Under the conditions of spontaneous redox reaction, chromium (Cr) is introduced for doping, and simultaneously, Na₂S₂O₃ dissolves in water to form a weakly alkaline solution, forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide on the surface of nickel foam in situ, thus obtaining a chromium-sulfur dual-doped nickel-iron layered double hydroxide / nickel foam catalyst. This invention features a simple preparation process, rapid synthesis, inexpensive and readily available raw materials, low cost, high yield, and environmental friendliness, making it suitable for large-scale production. The chromium-sulfur dual-doped nickel-iron layered double hydroxide uses nickel foam as the nickel source, and grows in situ on a nickel foam substrate, forming a three-dimensional porous nanosheet array structure. As a bifunctional water electrolysis catalyst, the chromium-sulfur dual-doped nickel-iron layered double hydroxide / nickel foam exhibits excellent oxygen evolution reaction activity and a low hydrogen evolution overpotential, demonstrating superior water electrolysis performance.

[0023] The chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst of this invention is used in the electrolysis of water to produce hydrogen. The electrolyte is a mixed solution of glucose and KOH. In this way, glucose serves as the anodic oxidation substrate, and the glucose undergoes an oxidation reaction at the anode, achieving an upgraded conversion of glucose and avoiding the generation of oxygen at the anode, thus avoiding the danger of oxygen and hydrogen mixing. At the same time, it can significantly reduce the potential required by the electrolyzer, thereby reducing the energy consumption for hydrogen production, promoting the development of water electrolysis, and ultimately achieving efficient hydrogen production. Attached Figure Description

[0024] Figure 1 The image is a scanning electron microscope (SEM) image of the chromium-sulfur double-doped nickel-iron layered double hydroxide prepared in situ on the surface of a nickel foam substrate in Example 3 of this invention.

[0025] Figure 2The X-ray photoelectron spectroscopy (XPS) of the chromium-sulfur double-doped nickel-iron layered double hydroxide prepared in situ on the surface of a nickel foam substrate in Example 3 of the present invention.

[0026] Figure 3 The oxygen evolution polarization curve (LSV) performance diagrams of the foamed nickel NF prepared in Example 3 of the present invention, and the chromium-sulfur double-doped nickel-iron layered double hydroxide and RuO2 grown in situ on the surface of the foamed nickel substrate.

[0027] Figure 4 The hydrogen evolution polarization curves (LSV) of the foamed nickel NF prepared in Example 3 of the present invention and the chromium-sulfur double-doped nickel-iron layered double hydroxide grown in situ on the surface of the foamed nickel substrate are shown.

[0028] Figure 5 The image shows the polarization curves (LSV) of water electrolysis and glucose electro-oxidation-assisted water electrolysis of the chromium-sulfur double-doped nickel-iron layered double hydroxide prepared in situ on the surface of a foamed nickel substrate in Example 3 of this invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0030] This invention discloses a method for rapidly preparing a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0031] Step 1: Immerse the nickel foam in acetone and ultrasonically clean for 10-20 minutes. Then, immerse the preliminarily cleaned nickel foam in 2-4 mol / L hydrochloric acid and ultrasonically clean for 10-20 minutes. Finally, rinse alternately with anhydrous ethanol and deionized water 2-5 times. Finally, vacuum dry at 20-35℃ for 8-12 hours to obtain nickel foam with the oxide layer removed.

[0032] Step 2: Weigh (3.5-4.5)g of Fe(NO3)3·9H2O and (0.05-0.5)g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 5-20 minutes at room temperature to form a homogeneous solution.

[0033] Step 3: Immerse the nickel foam from step (1) into the solution obtained in step (2) at room temperature, and then add (0.5-1.5) g of Na2S2O3. React at room temperature for 2-10 min.

[0034] Step 4: After the reaction is complete, the black product is removed and washed 2–6 times with anhydrous ethanol and deionized water, respectively. It is then vacuum dried at room temperature for 8–15 hours to obtain a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst. A bifunctional electrocatalyst is a catalyst that can simultaneously act on both the anodic oxygen evolution and the cathode hydrogen evolution reactions.

[0035] Example 1

[0036] This invention discloses a method for rapidly preparing a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0037] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0038] Step 2: Weigh 3.5g of Fe(NO3)3·9H2O and 0.05g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0039] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 0.5 g of Na2S2O3 is added. The reaction is carried out at room temperature for 2 min.

[0040] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0041] Example 2

[0042] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0043] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0044] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.1g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0045] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added and reacted at room temperature for 4min.

[0046] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0047] Example 3

[0048] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0049] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0050] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.3g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0051] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added and reacted at room temperature for 6min.

[0052] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0053] from Figure 1 SEM images show that the chromium-sulfur double-doped nickel-iron layered double hydroxide exhibits a three-dimensional porous nanosheet array structure.

[0054] from Figure 2 X-ray photoelectron spectroscopy reveals that the chromium-sulfur double-doped nickel-iron layered double hydroxide mainly contains Ni, Fe, Cr, O, and S elements. Furthermore, this invention utilizes the standard electrode potential Eq(Fe... 3+ / Fe 2+ )>Eq(Ni 2+ / Ni 0Under the conditions of spontaneous redox reaction, the introduction of cation Cr for doping, combined with the dissolution of Na2S2O3 in water to form a weakly alkaline solution, proves the successful preparation of chromium-sulfur double-doped nickel-iron layered double hydroxides.

[0055] Figure 3 The oxygen evolution polarization curves were measured in 1M KOH in a three-electrode system using nickel foam NF, chromium-sulfur double-doped nickel-iron layered double hydroxide (a self-supporting catalyst) grown in situ on the surface of a nickel foam substrate, and RuO2. Nickel foam NF, the chromium-sulfur double-doped nickel-iron layered double hydroxide (a self-supporting catalyst), and RuO2 were used as the working electrodes. It can be seen that the in-situ prepared chromium-sulfur double-doped nickel-iron layered double hydroxide exhibits excellent oxygen evolution reaction activity at 100 mA / cm². 2 Its oxygen evolution overpotential is 252mV, which is significantly lower than the overpotential required for nickel foam and commercial RuO2.

[0056] from Figure 4 The hydrogen evolution polarization curves of NF in foamed nickel and the chromium-sulfur double-doped nickel-iron layered double hydroxide grown in situ on the surface of foamed nickel substrate show that the chromium-sulfur double-doped nickel-iron layered double hydroxide has a low hydrogen evolution overpotential, reaching 10 mA / cm. 2 and 50mA / cm 2 The overpotentials at current densities are 132 mV and 214 mV, respectively, which are similar to those of nickel foam at 10 mA / cm². 2 and 50mA / cm 2 The overpotential at the current density is significantly reduced.

[0057] from Figure 5 The polarization curves of water electrolysis and glucose electrooxidation-assisted water electrolysis of chromium-sulfur double-doped nickel-iron layered double hydroxides grown in situ on the surface of a nickel foam substrate show that the glucose oxidation reaction can replace the oxygen evolution reaction at the anode. When the electrolyte is only 1M KOH solution, oxygen evolution and hydrogen evolution reactions occur, and the electrolytic cell reaches 10 mA / cm². 2 and 50mA / cm 2 The overpotentials at the points were 1.614V and 1.722V, respectively. When the electrolyte was a mixed solution of glucose and KOH, with a KOH concentration of 1M and a glucose concentration of 30mM, and glucose was used as the anodic oxidation substrate, the glucose underwent an oxidation reaction at the anode. At this point, the electrolytic cell reached 10mA / cm. 2 and 50mA / cm 2 The overpotentials at the anode and anodic oxidation were 1.337V and 1.56V, respectively. Glucose underwent a further conversion at the anode, avoiding oxygen production and thus preventing the danger of oxygen and hydrogen mixing. Therefore, replacing the oxygen evolution reaction at the anode with glucose oxidation significantly reduces the potential required for the electrolyzer, thereby reducing hydrogen production energy consumption.

[0058] Example 4

[0059] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0060] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0061] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.2g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0062] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added and reacted at room temperature for 8min.

[0063] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0064] Example 5

[0065] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0066] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0067] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.3g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0068] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added. The reaction is carried out at room temperature for 10min.

[0069] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0070] Example 6

[0071] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0072] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 20 min. Then, immerse the preliminarily cleaned nickel foam in 4 mol / L hydrochloric acid and ultrasonically clean for 20 min. Finally, rinse with anhydrous ethanol and deionized water alternately 5 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0073] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.25g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0074] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 0.5 g of Na2S2O3 is added. The reaction is carried out at room temperature for 6 min.

[0075] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0076] Example 7

[0077] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0078] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0079] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.35g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0080] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1.5g of Na2S2O3 is added and reacted at room temperature for 2min.

[0081] (4) After the reaction is complete, the black product is taken out and washed 6 times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 15 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0082] Example 8

[0083] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0084] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0085] Step 2: Weigh 3.5g of Fe(NO3)3·9H2O and 0.4g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0086] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added and reacted at room temperature for 6min.

[0087] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0088] Example 9

[0089] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0090] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 15 min. Then, immerse the preliminarily cleaned nickel foam in 3 mol / L hydrochloric acid and ultrasonically clean for 15 min. Finally, rinse with anhydrous ethanol and deionized water alternately 3 times. Vacuum dry at room temperature for 12 h to obtain nickel foam with oxide layer removed.

[0091] Step 2: Weigh 4g of Fe(NO3)3·9H2O and 0.45g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0092] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1g of Na2S2O3 is added and reacted at room temperature for 4min.

[0093] (4) After the reaction is complete, the black product is taken out and washed twice with anhydrous ethanol and deionized water respectively. The product is then dried under vacuum at room temperature for 8 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

[0094] Example 10

[0095] This invention discloses a method for rapidly forming a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst, comprising the following steps:

[0096] Step 1: Immerse the nickel foam in pure acetone and ultrasonically clean for 10 min. Then, immerse the preliminarily cleaned nickel foam in 2 mol / L hydrochloric acid and ultrasonically clean for 10 min. Finally, rinse twice with anhydrous ethanol and deionized water alternately. Vacuum dry at room temperature for 8 h to obtain nickel foam with oxide layer removed.

[0097] Step 2: Weigh 4.5g of Fe(NO3)3·9H2O and 0.15g of Cr(NO3)3·9H2O and add them to 100mL of deionized water. Stir magnetically for 10min at room temperature to form a homogeneous solution.

[0098] (3) At room temperature, the nickel foam from step (1) is immersed in the solution obtained in step (2), and then 1.5g of Na2S2O3 is added and reacted at room temperature for 2min.

[0099] (4) After the reaction is complete, the black product is taken out and washed three times with anhydrous ethanol and deionized water respectively. The product is then vacuum dried at room temperature for 12 hours to obtain the chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel bifunctional electrocatalyst.

Claims

1. The application of a chromium-sulfur dual-doped nickel-iron layered double hydroxide / foam nickel catalyst in hydrogen evolution through water electrolysis, characterized in that, The electrolyte used in the electrolysis of water to produce hydrogen is a mixed solution of glucose and KOH, with the concentration of KOH being 0.5~1.5 M and the concentration of glucose being 20~40 mM. The method for preparing the catalyst includes the following steps: S1, Fe(NO3)3·9H2O and Cr(NO3)3·9H2O were added to deionized water at a mass ratio of (3.5~4.5):(0.05~0.5) and stirred magnetically for 5~20 min. The ratio of deionized water to Fe(NO3)3·9H2O was 100 mL:(3.5~4.5) g, and a mixed solution was obtained. S2, the nickel foam to be treated is immersed in acetone and ultrasonically cleaned for 10-20 min to obtain pre-cleaned nickel foam. Then, the pre-cleaned nickel foam is immersed in 2-4 mol / L hydrochloric acid and ultrasonically cleaned for 10-20 min. After that, it is rinsed alternately with anhydrous ethanol and deionized water 2-5 times. Finally, it is vacuum dried at 20-35℃ for 8-12 h. The obtained nickel foam is immersed in a mixed solution, and then Na2S2O3 is added and reacted at room temperature for 2-10 min. The mass ratio of Na2S2O3 to Fe(NO3)3·9H2O in S1 is (0.5-1.5):(3.5-4.5). Chromium-sulfur double-doped nickel-iron layered double hydroxide grows in situ on the surface of the nickel foam to obtain a mixture. S3. The mixture in the reaction solution was washed 2-6 times with anhydrous ethanol and deionized water respectively, and then vacuum dried at room temperature for 8-15 h to obtain chromium-sulfur double-doped nickel-iron layered double hydroxide / foam nickel catalyst.

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