Preparation Of Vanadium-doped Nickel Foam Electrode And Its Catalytic Performance In Water Electrolysi

As the energy crisis and environmental problems continue to intensify,adjusting the energy structure and seeking new energy sources that are efficient,sustainable and clean are the inevitable choices for human society to achieve long-term development.As a renewable and clean energy source,hydrogen energy has the advantages of wide source,high combustion calorific value and non-polluting products,which can effectively replace traditional fossil fuels.Electrocatalytic water splitting as one of the methods to prepare high purity hydrogen is recognized as a very promising new energy technology.At present,precious metals are still the best performing materials in catalytic Hydrogen evolution reaction（HER）/oxygen evolution reaction（OER）,but the limited reserves and high prices limit their large-scale industrial applications.Therefore,the development of inexpensive,reserve-rich and efficient nickel-based catalytic materials has become a major research hotspot.Among them,vanadium has a higher abundance with more empty d orbitals in the earth’s crust,which is favorable to combine with other transition metal materials to obtain electrocatalytic materials with high activity.Therefore,improving the electrocatalytic performance of nickel-based electrodes by vanadium doping is important for the enhancement of catalytic performance of electrolytic water reactions.In this paper,vanadium pentoxide（V₂O₅）was dissolved in 1-butyl-3-methylimidazolium tetrafluoroborate（[Bmim]BF₄）,choline chloride-urea（Reline）,and choline-ethyleneglycol chloride（Ethaline）for the purpose of preparing vanadium-doped nickel-based electrodes with efficient electrolytic water catalytic capacity,and the electrochemical reduction of V₂O₅ was studied by cyclic voltammetry.After analyzing and comparing the deposited products,V₂O₅-Ethaline was selected as the electrolyte for the preparation of vanadium-doped nickel foam electrodes,and the correspondence between the product morphology and the electrodeposition parameters was determined by controlling the deposition conditions.In addition,the electrolytic water catalytic performance of the obtained vanadium-doped nickel foam electrode was characterized by cyclic voltammetry,linear voltammetry scanning method and AC impedance method under alkaline environment,and the influence laws of time,temperature,V₂O₅concentration and tank voltage on the catalytic performance of the electrode during the electrodeposition process were investigated.The main research results are as follows:（1）Irregularly agglomerated granular vanadium with a particle size of about 1-2μm is electrodeposited on nickel foam in V₂O₅-[Bmim]BF₄ at 80°C.Irregularly flaked vanadium with a particle size of about 2-4μm is electrodeposited on nickel foam in V₂O₅-Reline at 80°C.The electrodeposition of irregular vanadium flakes with particle size of about 2-4μm on nickel foam in V₂O₅-Ethaline at 80°C resulted in the electrodeposition of three-dimensional porous vanadium nanosheets with particle size of about 1-2μm,which is favorable for the electrolytic water reaction.Therefore,V₂O₅-Ethaline was finally selected as the electrolyte for the preparation of vanadium-doped nickel foam electrodes..（2）The electrodeposition time,temperature,V₂O₅ concentration and voltage have significant effects on the product morphology when preparing vanadium-doped nickel foam electrodes in V₂O₅-Ethaline electrolyte.The analysis of scanning electron microscope images shows that the flakes accumulate into granules with increasing electrodeposition time,and the particles keep increasing and showing the tendency of aggregation.Increasing the electrodeposition temperature is beneficial to the tighter and more uniform surface morphology of nickel foam.Increasing the V₂O₅ concentration changes the surface morphology from granular to flaky.As the deposition voltage increases,the surface morphology remains flaky,but the nanosheet size becomes larger.（3）The composition of the vanadium-doped nickel foam electrode was analyzed by XRD,and it was found that the vanadium-doped nickel foam electrode nanosheets consisted of Ni VO₃and VO（OH）₂,and the typical characteristic peaks of Ni²⁺,metal oxides（O1s）,V⁴⁺was found by XPS.vanadium alloy oxide films including VO（OH）₂ and Ni VO₃ on the surface of the nickel foam substrate.（4）The electrodeposition time,temperature,V₂O₅ concentration,and voltage had significant effects on the electrolytic water catalytic activity of the electrode during the preparation of vanadium-doped nickel foam electrode in V₂O₅-Ethaline electrolyte.The catalytic activity of the electrode increased with the increase of the electrodeposition time,and the catalytic activity was best at 20 h of the deposition time.The catalytic activities of HER and OER of the electrode increased with the increase of electrodeposition temperature,and the best catalytic activity was achieved at the electrodeposition temperature of 140℃.The HER catalytic activity of the electrode increased with the increase of V₂O₅ concentration,and the OER catalytic activity was best at the V₂O₅ concentration of 0.06 mol/L.The HER and OER catalytic activities of the electrodes became stronger and then weaker with increasing electrodeposition voltage,and were best at a voltage of 3.2 V.（5）Under the optimal deposition conditions,the vanadium-doped nickel foam electrode requires a HER overpotential of 167 m V and a Tafel slope of 115.1 m V/dec and an OER overpotential of 232 m V and a Tafel slope of 50.1 m V/dec to reach a current density of 10 m A cm^-2,and can operate as the anode oxygen precipitator for 353 h at a current density of 10 m A cm^-2.performance is better than most of the reported Nickel-based catalysts.The easy preparation process and the excellent catalytic activity of vanadium-doped nickel-based electrodes,as well as their strong durability,are expected to ensure their practical application in electrolytic water installations.