The Preparation Of Iron-based Electrode Materials And Their Properties Of Water Splitting

In order to meet the huge demand for energy in modern society,people need to constantly explore the development of sustainable,green new energy.Hydrogen is ideal for replacing traditional fossil fuels with high energy density and renewables.At present,electrolyte water is considered to be one of the most promising large-scale hydrogen production technologies because of its abundant resources,no greenhouse gas emissions and high purity of hydrogen production.The design and preparation of electrolytic water catalysts with high catalytic activity and stability is the key to technology.Precious metals such as platinum palladium are known to be the ideal electrolyte catalysts,but are limited by their high cost and low reserves.Therefore,the electrocatalyst of non-precious metals has become the focus of research in recent years.Iron metal-based electrode materials are favored by scientists because of their abundant reserves,low price and good electrochemical properties.The traditional studies on the design of iron metal-based electrode materials are limited to the intrinsic activity of catalysts.In recent years,it has become a hot research project for researchers to further improve the catalytic activity of electrode materials by combining strategies to increase the active sites of catalysts,including building defects,doping,heterojunctions,etc.In this study,a thin array structure of ultra-thin nickel hydroxide nanosheets with rich edges is prepared in-situ on nickel foam by simple and environmentally friendly acid etching.Subsequently,three kind of water electrolysis catalysts were prepared by means of ion doping and construction defects:（1）The ultra-thin Ni（OH）₂nanosheets array precursor were prepared on nickel foam（NF）by in-situ acid etching method,and then the first porous Ni₂P nanosheets array inset with Ni₂P nanoparticles were prepared using the Kirkendall effect and Oswald ripening theory for the first time,and the theoretical basis for the synthesis of catalysts was confirmed by physical characterization such as HRTEM,SEAD and XRD.The catalyst has excellent HER and OER electrocatalytic activity and good stability due to its rich active sites,and its OER performance is comparable to that of the precious metal Ru O₂.In a two-electrode system,Ni₂P/NF is assembled as a cathode and anode in a fully deconsolved hydropower solution tank at 1.63V to obtain a current density of 10 mA cm^-2.（2）Co-doped Ni（OH）₂/NF and Fe-doped Ni（OH）₂/NF nanosheet arrays were prepared by ion doping method as high-efficiency electrode materials in asymmetric electrolyzers.Due to the synergistic effect between Ni（OH）₂ and high valence Co and Fe,the overpotential of water electrolysis is greatly reduced,the kinetic efficiency is improved,and the catalytic activity is extremely high.In the two-electrode system,the assembled asymmetric electrolyzer shows the same catalytic activity and good stability as Pt C//Ru O₂,which can reach a current density of 10 mA/cm² at 1.59 V,and can operate stably for more than 24 hours without obvious performance degradation,showing a good application prospect.（3）Bimetallic phosphide Ni₂P/NiFeP/NF nanosheet arrays with rich grain boundaries were synthesized by combining acid etching,ion doping and static vapor phosphating.By constructing rich grain boundaries on NiFe-based catalysts with high intrinsic activity.The Ni₂P/NiFeP/NF catalyst exhibits excellent oxygen evolution activity,and the current density can reach 50 mA/cm² only with an overpotential of 240 m V.In order to find out the influencing factors of the activity decline of phosphide catalyst during long-term service.Through XRD,HRTEM,SEAD and other physical characterization combined with electrochemical performance test,we explored the reason and mechanism of inactivation of transition metal phosphide after long-term stability test.