Preparation Of NiSe₂ Electrode Materials And Corresponding Electrochemical Properties

With the gradually use of fossile fuel and the serious environment pollution,the percentage of renewable green energy is keeping increasing in national energy structure.While the energy sturcture need to be upgraded,the transportation and storage of the energy need to be improved simultaneously due to the unstorable electric energy.On this basis,producting high purity hydrogen energy through electrolysis of water becomes one of the key point in energy transformation.Electrolysis of water is a way to utilize the electirc power to accelerate the decomposition of water molecule by catalytic electrodes.In the process of water splitting,the reaction potential is much higher than theorical voltage under the influence of reaction barrier.Electrocatalysis can effectively reduce the reaction barrier so as to improve the energy efficiency.Now,studies of the catalysts focus on modifying the catalysts'intrinsic activity by different means after building the nanostructure.So,NiSe₂ nanosheets are chosed as precursors in this article,aiming at making use of its high conductivity and boost its poor intrinsic activity,to craft three different electrode catalysts by core-shell constucting,heteroatom doping and noble metal decorating.To boost the sluggish reaction in OER processs,chemical bath is used to consturcting a thin film containing Fe element on the surface of NiSe₂ nanosheets and reserve the high conductivity of NiSe₂.After that,a high temperature phosphorization process is induced to construct NiSe₂/Ni₂P@FeP bifunctional catalyst with rich nanointerfce.Because of the highly elevated conductivity due to the rich nanointerface and synergistic effect between Ni and Fe,NiSe₂/Ni₂P@FeP catalyst only need 202 mV overpotential to achieve 10 mA cm^-2 current density.Further,when use the NiSe₂/Ni₂P@FeP catalyst as both anode and cathode in overall water splitting,cell voltage at 1.554 V is needed to achieve 10 mA cm^-2 current density.To further improve the intrinsic activity of NiSe₂,the way of plasma assisted P doping is used to construct A-NiSe₂|P catalyst with defects and heteroatoms.When Plasma is used,the phosphorization time of the sample sharply reduced,from 90min to5min.What's more,Se vacancy is induced in plasma etching process.A-NiSe₂|P catalyst need 111 mV to gain 10 mA cm^-2 current decsity and the improvement of HER performance is the result of lower Gibbs free energy of Ni,Se,P active site due to the interaction among Se vacancy,P heteroatom and Ni,Se atoms in NiSe₂,in other words,the intrinsic activity of active sites in A-NiSe₂|P has been optimized.When A-NiSe₂|P sanples are used as anode and cathode in overall water splitting system,cell voltage at1.620 V is needed to achieve 10 mA cm^-2 current density.Finally,because of the high conductivity of NiSe₂,regarding NiSe₂ nanosheets as noble metal atoms'carrier,reduced Pt/Ir nanocrystal is successfully induced on the surface of NiSe₂ nanosheets.Through the electrochemical tests,the improment of Pt/Ir-NiSe₂|E is on account of noble metal atoms and the quicker electric transport ability.Pt/Ir-NiSe₂|E only need 104 mV and 196 mV to achieve 10 mA cm^-2 current density on the side of HER and OER,respectively.When Pt/Ir-NiSe₂|E catalysts are used as both anode and cathode in overall water splitting system,cell voltage at 1.546 V is needed to achieve 10mA cm^-2 current density.Further more,the stability of Pt/Ir-NiSe₂|E is proved after a long-hours test without any potential changes,which also proves the Pt/Ir atoms formed a permanent chemical bond with NiSe₂ through chemical bath and plasma etching effects.