Preparation Of Nickel-based Catalysts And Study Of Their Electrocatalytic Water Splitting Performanc

Electrochemical water splitting is composed of hydrogen evolution reaction(HER)at the cathode and oxygen evolution reaction(OER)at the anode.And there are some kinetic obstacles in both reactions.Therefore,catalysts are needed to reduce the overpotential.Nickel is a low cost non-precious metal with good water splitting activity and development prospect.However,it is still limited by the lack of active sites and other problems.Based on the purpose of optimizing catalysts activity,nickel-based polymetallic catalysts were manufactured by electrochemical method:NiCu and NiFe catalysts were successfully prepared,and their structures and catalytic performance of water splitting were systematically researched:(1)Based on the synergistic effect of Ni and Cu,the NiCu parent alloy was prepared.Subsequently,in order to expose the active sites,dealloying combined with electrochemical anodization was used to prepare manufacture porous NiCu nanoneedle arrays catalyst(p-NiCu NAs).The crystal structure,surface morphology and component proportion of the p-NiCu NAs were rpectively analysed by XRD,SEM and EDS,revealing the it is composed of the base metal and oxide/hydroxide.The linear scanning voltammetric method was used to test the HER performance of p-NiCu NAs.In 0.1 M KOH,the overpotential reaching 10 mA·cm-2 is 92 mV,and the Tafel slope is 66 mV·dec-1.In addition,the authors also tested the OER activity of pNiCu NAs,and found that the OER performance of the anodic activation product p-NiCu NAs does not significantly enhance,and the electron transfer rate decreases with the development of OER,resulting in activity attenuation.(2)A porous NiCuTi nanosheet arrays catalyst(p-NiCuTi NAs)was prepared by etching Ni40Cu50Ti10 parent alloy.XRD,SEM,EDS and XPS were used to analyze the crystal structure,surface structure morphology,metal proportion and surface chemical valence state of the catalyst electrode material,revealing that the introduction of Ti leads to the mass dissolution of Cu components and the formation of an open structure,which further optimizes the reaction kinetics,the number of active sites and the intrinsic activity.Showing good HER activity in 1 M KOH,p-NiCuTi NAs needs 48 mV and 124 mV to reach10 mA·cm-2 and 100 mA·cm-2.respectively.Also,its Tafel slope is only 55 mV·dec-1.(3)Using electrochemical anode deposition,binnary Ni-based oxide(NiFeOx)was prepared.XPS and XRD were used to analyze the chemical valence and crystal structure of the prepared catalysts.NiFeOx has a good OER activity,and its onset overpotential is as low as 300 mV in 0.1 M KOH,with a Tafel slope of 38 mV·dec-1.Combined with electrochemical impedance and electrochemical surface area tests,it was revealed that the introduction of Fe not only accelerates electron transfer,but also regulates the number of active sites and intrinsic activity of NiFeOx,thus promoting progress of OER.