Preparation And Electrocatalytic Properties Of Catalysts For Nickel-Based Intermetallic Compounds

Due to the increasing consumption of fossil fuels and pollution to the environment,researchers are working hard to exploit renewable energy of highly efficient and clean.Electrocatalytic water splitting has attracted attention all over the world for its promising applications in alleviating energy shortages and environmental pollution.The electrocatalytic process requires energy consumption to drive the reaction.The electron transfer kinetics of HER is relatively simple.While OER involves relatively complex multi-step electron transfer kinetics,which is a slowly dynamic and highly energy-intensive.Therefore,it is essential to develop suitable electrocatalysts to effictively carry out the electrochemical process,to achieve the goal of high current densities at relatively low overpotentials.Despite the fact that a handful of electrocatalysts have superior performance,the high cost and low electrochemical stability of the raw materials have consistently been unfavorable to their development of industrial.As promising substitutes for Pt-,Ir-and Ru-based catalysts,the non-noble metal catalysts have been widely studied due to their good catalytic activity and long-term stability.The purpose of this paper is to prepare inexpensive Ni-based catalyst materials by simple synthesis methods(such as solid-state synthesis method and arc-melting technique)to improve the performance of electrocatalytic water splitting,detailed three parts are listed as follows:1.A simple solid-state synthesis method was used to synthesize Ni-Sn compounds with Ni and Sn as raw materials.The structure,surface morphology and chemical constitution of the samples were characterized by X-ray diffraction(XRD),scanning electron microscope(SEM,X-ray photoelectron spectroscopy(XPS),respectively.The catalytic activity of the electrocatalysts were studied in detail through electrochemical tests,including linear scanning voltammetry(LSV),cyclic voltammetry(CV),chronoamperometry(CA),electrochemical impedance method(EIS),etc.The results showed that Ni3Sn had the best catalytic performance compared with Ni3Sn2 and Ni3SN4 in alkaline solution(1M KOH),with the current density of 10 mA/cm2,the overpotential of Ni3Sn is 304 mV,which is lower than that of Ni3Sn2 and Ni3Sn4.In the process of OER reaction,there is a transition of nickel oxyhydroxide on the surface of the sample and the structure remains stable,the catalysts feature great stability and maintain stable current density even after 12 h of continuous operation;moreover,Ni3Sn has good oxygen evolution reaction performance in acidic solution(1 M H2SO4).In general,whether in alkaline solution or acidic solution,Ni3Sn has shown a good performance in the oxygen evolution reaction.With the difference of the molar ratio of Ni/Sn,the catalysts show different performances.In the 1 M KOH or 1 M H2SO4 solution,the order of catalytic activity is as follows:Ni3Sn>Ni3Sn2>Ni3Sn4.2.Ni,Fe,and Sn as raw materials,Ni-Fe-Sn compounds with hexagonal crystal system were synthesized based on Ni3Sn2 by solid-state synthesis.The performances of the catalysts with different proportions of Fe in the oxygen evolution were studied though techniques such as structural characterization and electrochemical testing.The prepared NiFe2Sn2 catalyst showed excellent OER activity performance.The overpotential was only 266 mV at a current density of 10 mA/cm2,and Tafel slope was 45 mV/dec at the current density of 100 mA/cm2.In summary,with the addition of Fe,the structure of Ni-Fe-Sn compounds are well maintained and OER catalytic performance is improved to some extent,the order of catalytic activity is as follows:NiFe2Sn2>Ni2Fe2Sn2>Ni3Sn2.3.The RE-Ni(RE=Tb,Dy,Ho)compound of hexagonal structure was prepared by arc-melting technique using rare earth elements and Nickel as raw materials.The surface morphology and phase of the material are studied by physical characterization,and the electrochemical hydrogen evolution reaction of the catalyst is studied by a series of electrochemical test methods.Due to the contraction of the lanthanide,the catalyst of TbNi5 had lower overpotential,smaller Tafel slope,lesser charge transfer resistance,which showed good HER catalytic activity in 1 M KOH alkaline solution,and maintained basically loss-free catalytic stability for at least 12 h,the sequence of the catalysis active:TbNi5>DyNi5>HoNi5.