Preparation method of multi-element doped ferronickel oxyhydroxide oxygen evolution electrode

Abstract

The invention relates to a preparation method of a multi-element doped ferronickel oxyhydroxide oxygen evolution electrode. The method comprises the following steps: (1) dissolving ferric nitrate, nickel nitrate, metal salt, ammonium fluoride and urea into deionized water, and reacting after sealing to obtain a multi-element doped ferronickel layered hydroxide; (2) under a three-electrode system, taking the obtained multi-element doped nickel-iron layered hydroxide as a working electrode, taking Hg / HgO as a reference electrode, and taking a carbon rod as a counter electrode; and electrolyzing for 15-25 hours under the constant current of 5-20 mA cm <-2 > to obtain the multi-element doped nickel-iron oxyhydroxide. The obtained multi-element doped nickel-iron oxyhydroxide has a sharp-edge nanosheet morphology, and the stability of the multi-element doped nickel-iron oxyhydroxide is improved by 27 times compared with that of a nickel-iron oxyhydroxide electrocatalyst when the multi-element doped nickel-iron oxyhydroxide electrocatalyst is used for electrocatalytic oxygen evolution.

Description

Technical Field

[0001] The invention relates to a method for preparing a multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode, belonging to the field of electrocatalysis. Background Art

[0002] The development of sustainable energy technologies can significantly alleviate the energy crisis and environmental pollution. Electrochemical water splitting driven by solar and wind energy is a promising renewable energy source for obtaining hydrogen, which can replace traditional fossil fuels. However, due to the slow kinetics of the anodic oxygen evolution reaction (OER), the process has a high overpotential, which involves a complex four-electron process. Currently, RuO 2 Materials are the benchmark for OER electrocatalysts. However, the high cost and scarcity of these elements greatly hinder their industrial-scale utilization. Therefore, it is crucial to find highly active, stable, and cost-effective OER electrocatalysts.

[0003] Nickel-iron oxyhydroxide exhibits high OER catalytic activity in alkaline environments and is considered to be a promising alternative to noble metal-based electrocatalysts and the best non-noble metal catalyst for OER activity. However, due to the weak Fe-O bond during the OER process, the active Fe is easily leached, resulting in a rapid decrease in the activity of nickel-iron oxyhydroxide and poor stability, which affects the development of industrial large-scale hydrogen production. Therefore, it is crucial to modify nickel-iron oxyhydroxide and improve its stability while ensuring its activity for large-scale water electrolysis to produce hydrogen. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode in view of the limitations of current technology. The method produces a high entropy effect by multi-element doping, thereby obtaining a multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode that can maintain high stability during the OER process. Among them, multi-element doping (five kinds) is to make the catalyst produce a high entropy effect so that the nickel-iron oxyhydroxide has high stability. The specific principle is that multi-element doping reduces the overall internal energy of the material and enhances the bonding of the metal-oxygen bond, so that the active nickel and iron atoms are not easy to escape, thereby maintaining the stability of the material during the catalytic process. The multi-element doped nickel-iron oxyhydroxide obtained by the present invention has high activity and high stability during the oxygen evolution reaction.

[0005] The technical solution of the present invention is:

[0006] A method for preparing a multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode, the method comprising the following steps:

[0007] (1) dissolving iron nitrate, nickel nitrate, mixture A, ammonium fluoride and urea in deionized water, transferring the solution to a reaction kettle after dissolution, adding carbon cloth to the reaction kettle, sealing the reaction kettle and keeping the temperature at 110 to 130° C. for 5 to 7 hours to obtain a multi-element doped nickel-iron layered hydroxide grown on a carbon cloth support;

[0008] Wherein, mixture A is a metal salt, which is any five of vanadium chloride, chromium nitrate, manganese nitrate, cobalt nitrate, niobium chloride, copper nitrate, and zinc nitrate; 0.25mmol iron nitrate, 1.9mmol nickel nitrate, 0.1mmol mixture A, 4mmol ammonium fluoride, 10mmol urea and 2-5cm 2 of carbon cloth; each metal salt in mixture A is 0.02 mmol;

[0009] (2) In a three-electrode system, the obtained multi-element doped nickel-iron layered hydroxide was used as the working electrode, Hg / HgO was used as the reference electrode, and a carbon rod was used as the counter electrode; at 5-20 mA cm -2 Electrolyze for 15 to 25 hours at a constant current to obtain multi-element doped nickel-iron oxyhydroxide;

[0010] The electrolyte is 0.5-2M KOH; the multiple elements are any five of vanadium, chromium, manganese, cobalt, niobium, copper and zinc;

[0011] The multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode obtained by the method is used for electrolyzing water to produce hydrogen, and the multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode serves as a working electrode.

[0012] The purity of the ferric nitrate is ≥99%, the purity of the nickel nitrate is ≥99%, the purity of the metal salt is ≥99%, the purity of the ammonium fluoride is ≥99%, and the purity of the urea is ≥99%.

[0013] Beneficial effects of the present invention:

[0014] The multi-element doped nickel iron oxyhydroxide prepared by the method has higher efficiency than nickel iron oxyhydroxide catalyst. The multi-element doped nickel iron oxyhydroxide synthesized by the method has a sharp-edge nanosheet morphology, and its stability is 27 times higher than that of nickel iron oxyhydroxide electrocatalyst during electrocatalytic oxygen evolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the X-ray diffraction (XRD) pattern of Example 1;

[0016] Figure 2 is a scanning electron microscope (SEM) image of Example 1;

[0017] Figure 3is the polarization curve (LSV) diagram of Example 1;

[0018] Figure 4 This is the stability test (it) diagram of Example 1. DETAILED DESCRIPTION

[0019] The purity of the iron nitrate, nickel nitrate, vanadium chloride, chromium nitrate, manganese nitrate, cobalt nitrate, niobium chloride, copper nitrate, zinc nitrate, ammonium fluoride and urea involved in the present invention is ≥99%, and the manufacturer is Shanghai Aladdin Company. The present invention uses RIGAKU SmartLab X-ray diffractometer to obtain XRD patterns. The instrument uses Cu Kα as the anode target, the X-ray power is 2kW, and the scanning speed is 6° min -1 , the scanning range is 10°~80°; the SEM images were obtained using a FEIQuanta-450 FEG field emission scanning electron microscope; and the LSV and it tests were performed using a Chenhua CHI 660E electrochemical workstation.

[0020] Example 1

[0021] First, 0.25mmol iron nitrate, 1.9mmol nickel nitrate, 0.02mmol vanadium chloride, 0.02mmol chromium nitrate, 0.02mmol manganese nitrate, 0.02mmol cobalt nitrate, 0.02mmol niobium chloride, 4mmol ammonium fluoride and 10mmol urea were dissolved in 35mL deionized water. After complete dissolution, the above solution was transferred to the reactor, and a piece of carbon cloth (1x3cm) was placed in the reactor. 2 ) and kept at 120°C for 6 hours. After the heat preservation, a multi-element doped nickel-iron layered hydroxide loaded on the carbon cloth was obtained (with a loading of about 3 mg cm -2 ), rinsed three times with deionized water and dried. In a three-electrode system, the dried multi-element doped nickel-iron layered hydroxide loaded on carbon cloth was used as the working electrode, Hg / HgO was used as the reference electrode, and the carbon rod was used as the counter electrode. The electrolyte was 10 mA cm -2 It was tested for 20 hours at a current density of , and multi-element doped nickel iron hydroxide oxide (NiFe(VCrMnCoNb)LDH) was obtained.

[0022] XRD pattern ( Figure 1 ) shows that the synthesized multi-element (vanadium, chromium, manganese, cobalt, niobium) doped nickel iron hydroxide has a crystalline structure, which conforms to the phase structure of FeOOH, proving the successful synthesis of the material. SEM image ( Figure 2 ) showed that multi-element doped NiFe oxyhydroxide grew on carbon cloth in the form of vertically interlaced sharp nanosheets.

[0023] Chenhua electrochemical workstation was used to test the OER of multi-element doped nickel iron hydroxide using a three-electrode system. The reference electrode was Hg / HgO, the counter electrode was a carbon rod, and the working electrode was multi-element doped nickel iron hydroxide. The test voltage range was 0-0.8V, and the scan rate was 2mV s -1 , IR compensation is 95%. LSV curve ( Figure 3 ) showed that multi-element doped nickel iron oxyhydroxide has a current density of 10 mA cm -2 The overpotential is only 251mV (electrocatalytic test in 1M KOH electrolyte), which shows excellent electrocatalytic oxygen evolution activity compared with other reported transition metal-based catalysts. Figure 4 ) shows that multi-element doped nickel iron oxyhydroxide has a high conductivity at 200 mA cm -2 It can work stably for 20 hours at a current density with almost no activity decay. Compared with other reported transition metal-based catalysts, it has excellent electrocatalytic oxygen evolution stability. This is because the high lattice distortion caused by the mixing of multiple elements enhances the bonding of metal-oxygen bonds, making the active metal iron difficult to leach, thus maintaining the structure and electrochemical stability of the electrode.

[0024] Comparative Example 1

[0025] The other steps are the same as those in Example 1, except that the precursor chemicals are not added, and chromium nitrate, vanadium chloride, manganese nitrate, cobalt nitrate, and niobium chloride are not added. The obtained product is different from that in Example 1, and nickel iron hydroxide nanosheets without doping elements are obtained. The nickel iron hydroxide nanosheets without doping elements have poor stability due to the absence of high lattice distortion.

[0026] Comparative Example 2

[0027] The other steps are the same as in Example 1, except that the time of the IT test is changed from 20 hours to 30 hours. The obtained product is different from Example 1. If the test time is too long, the multi-element doped nickel iron oxyhydroxide will be over-oxidized, and the obtained multi-element doped nickel iron oxyhydroxide nanosheets are thicker. The thicker nanosheets affect the mass transfer process and are not conducive to the OER performance of the catalyst.

[0028] Example 2

[0029] The other steps are the same as those in Example 1, except that the holding time at 120° C. is changed from 6 hours to 5 hours;

[0030] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0031] Example 3

[0032] The other steps are the same as those in Example 1, except that the holding time at 120° C. is replaced from 6 hours to 7 hours;

[0033] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0034] Example 4

[0035] The other steps are the same as in Example 1, except that the insulation temperature in the reactor is replaced from 120°C to 110°C;

[0036] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0037] Example 5

[0038] The other steps are the same as in Example 1, except that the insulation temperature in the reactor is replaced from 120°C to 130°C;

[0039] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0040] Example 6

[0041] The other steps are the same as in Example 1, except that -2 The electrolysis time under constant current was changed from 20 hours to 15 hours;

[0042] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0043] Example 7

[0044] The other steps are the same as in Example 1, except that -2 The electrolysis time under constant current was changed from 20 hours to 25 hours;

[0045] The morphology and catalytic performance of the obtained material are close to those of Example 1;

[0046] Matters not covered by the present invention are known technologies.

Claims

1. A method for preparing a multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode, characterized in that The method comprises the following steps: (1) dissolving iron nitrate, nickel nitrate, mixture A, ammonium fluoride and urea in deionized water, transferring the solution to a reaction kettle after dissolution, adding carbon cloth to the reaction kettle, sealing the reaction kettle and keeping the temperature at 110 to 130° C. for 5 to 7 hours to obtain a multi-element doped nickel-iron layered hydroxide grown on a carbon cloth support; Wherein, mixture A is a metal salt, which is any five of vanadium chloride, chromium nitrate, manganese nitrate, cobalt nitrate, niobium chloride, copper nitrate, and zinc nitrate; 0.25mmol iron nitrate, 1.9mmol nickel nitrate, 0.1mmol mixture A, 4mmol ammonium fluoride, 10mmol urea and 2-5cm 2 of carbon cloth; each metal salt in mixture A is 0.02 mmol; (2) In a three-electrode system, the obtained multi-element doped nickel-iron layered hydroxide was used as the working electrode, Hg / HgO was used as the reference electrode, and a carbon rod was used as the counter electrode; at 5-20 mA cm -2 Electrolyze for 15 to 25 hours at a constant current to obtain multi-element doped nickel-iron oxyhydroxide; The electrolyte is 0.5-2M KOH.

2. The method for preparing the multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode according to claim 1, characterized in that The purity of the ferric nitrate is ≥99%, the purity of the nickel nitrate is ≥99%, the purity of the metal salt is ≥99%, the purity of the ammonium fluoride is ≥99%, and the purity of the urea is ≥99%.

3. Application of the multi-element doped nickel-iron oxyhydroxide oxygen evolution electrode obtained by the method as claimed in claim 1, characterized in that it is used as a working electrode in hydrogen production by electrolysis of water.

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