Construction Of Transition Metal-based Composite Electrode And Its Performance In Water Electrolysis

In the past few decades,with the continuous development of society,the human need for renewable energy has been increasing.Compared with non-renewable energy sources,hydrogen energy is an ideal clean energy source for sustainable development in the future with its high calorific value and environmental friendly features.Currently,hydrogen preparation by electrolysis of water is the most reliable method.The process consists of two half-reactions,oxygen evolution reaction（OER）at the anode and hydrogen evolution reaction（HER）at the cathode.Using efficient and inexpensive catalysts can reduce the energy consumption problem in the water electrolysis process.Today,commercially available catalytic materials are mainly precious metals,but the scarcity and high cost of precious metals largely limit its application on a large scale.Apart from precious metals,transition metal-based catalysts have good physical and chemical properties and have good catalytic performance,which are highly favored by researchers.Based on the above considerations,this paper is oriented to improve the performance of a transition metal-based catalysts.The nickel foam was selected as the base material,and the number and distribution of active sites were increased by controlling interface and doping element.Finally,the electron transfer capacity of the catalytic electrodes was improved,and three catalytic electrodes with excellent performance were obtained.The specific research contents are as follows:1.Mo S₂/Ni（OH）₂/NF composite electrode was applied to OER catalysis.The Mo S₂/Ni（OH）₂/NF was prepared by a two-step hydrothermal/solvothermal method.The results of XPS analysis showed that the peak shift phenomenon occurred in Ni and Mo,indicates that the electron density of Ni and Mo ions has changed.The electrons are redistributed on the electrode interface,effectively accelerate the reaction speed and obtain higher catalytic activity.The overpotential of the composite electrode was 314 m V at the current density of 100 m A cm^-2,and the Tafel slope was 63 m V dec^-1.The excellent electrochemical performance was attributed to the self-supporting effect of NF and the synergistic effect between the heterostructures.2.Ni（OH）₂/Co Fe LDH/NF composite electrode was applied to OER catalysis.The experiment was prepared by electrodeposition and impregnation,and heterostructure was formed between Co Fe LDH and Ni（OH）₂ to achieve efficient catalysis of oxygen evolution reaction.The overpotentials of current densities at 50 and 100 m A cm^-2 were 280 m V and 290 m V,and the Tafel slope was 44 m V dec^-1.The XPS analysis showed that strong electronic interactions existed at the heterogeneous interface,which effectively modulated the electronic structure of the composite electrode and thus improved the OER catalytic activity.In addition,the electrode was reconstructed during the prolonged OER process,and the new active substance Ni OOH was generated.3.Fe-Ni₃S₂/NF integrated electrode was applied to OER catalysis.It was prepared quickly and easily using one-step electrodeposition method.The experiment was carried out to improve the catalytic activity of the Ni₃S₂ electrode by controlling the amount of Fe introduced.The electrochemical performance with different doping amounts was tested,and the doping concentration of 8%has the highest OER catalytic performance.The analysis showed that the doping of Fe caused the transfer of electrons from Ni to Fe,which reduced the electron density around Ni ions.Therefore,the electronic structure of Ni₃S₂ is effectively regulated and the catalytic activity of OER is improved.At the same time,during the OER test,the enrichment of surface S promoted the formation of Ni OOH,which further improved the catalytic performance.