Preparation Of Transition Metal Nickel-based Self-supporting Electrodes And Study Of Their Seawater Splitting Performanc

Seawater is abundant in the world’s water resources and hydrogen is a green and sustainable energy with high energy density.Electrochemistry is a promising technology for producing hydrogen without carbon emission,which direct electrolysis of seawater to produce hydrogen will have a positive impact on energy and environment.The electrode is an important factor in the electrochemical process.In this paper,we investigate the chemical composition and microstructure of electrode materials.Firstly,the carbon felt with good electrical conductivity and strong stability is choiced as the substrate,then nickel base compound is grown on its surface in situ by adjusting its active proportion,metal coordination and internal structure.Finally,two selfsupported transition metal nickel-based hydroxide(CF@BCC@MOF-LDH)and nickel-based oxide(CF@Ni Mo O4@Ni Fe2O4)dual-function electrodes with excellent performance are designed through morphology,structure and electrochemical performance analysis.The prepared electrodes make full use of the characteristics of multistage and heterogeneous heterogeneous structure.It has the advantage of industrial high current and excellent performance in the application of seawater cracking.The details are as follows:(1)A hollow nanocage-structured nickel-cobalt dihydroxide self-supported electrode(CF@BCC@MOF-LDH)is grown in situ on carbon felt by hydrothermal and impregnation methods.Due to the unique hollow nanocage structure,the active surface area of the electrode can be maximized,which is conducive to the transfer and diffusion of electrons at the interface,thus significantly reducing the overpotential in the reaction.For the hydrogen evolution,the overpotential of CF@BCC@MOF-LDH electrode at10 and 400 m A cm-2 is 89 and 356 m V,respectively.For the oxygen evolution reaction,the overpotential of CF@BCC@MOF-LDH electrode at 10 and 400 m A cm-2 is 182 and 443 m V,respectively.At the same time,CF@BCC@MOF-LDH as a dual-function electrode can reach 10 and 400 m A cm-2 when the operating voltage is 1.516 and 1.973 V,respectively.In addition,the electrode also has 99% Faraday efficiency and 102 h splitting stability.(2)A novel three-dimensional core-shell heterogeneous Ni based polymetallic oxide CF@Ni Mo O4@Ni Fe2O4 electrode is prepared.Firstly,the carbon felt is modified by acid to increase its hydrophilicity.Secondly,a dual-function electrode with high activity and durability is prepared by hydrothermal,impregnation and calcination methods for alkaline seawater splitting.For the hydrogen evolution reaction,the current density reaches 10 and 400 m A cm-2,and the required overpotential is 37 and 292 m V.For the oxygen evolution reaction,the current density reaches 10 and 400 m A cm-2,and the required overpotential is only 139 and 356 m V.Therefore,the electrode has excellent properties of hydrogen and oxygen evolution.The catalytic activity of the electrode is better than that of the reference electrode pair when it is used as a dualfunction electrode in seawater splitting,and the splitting voltage is only 1.414 and 1.945 V,reaching 10 and 400 m A cm-2.In addition,the selectivity of the anode in the splitting process is very high,which can reach nearly 100% Faraday efficiency and has more than 200 h splitting stability.