Preparation And Electrocatalytic Performance Of Co,Ni-based Selenides For Water Splitting

Recently,this is important study on how to reduce the energy consumption during water splitting and improve the durability of the catalyst.At first,the noble metal-base catalysts have been paid more attention,because of their excellent performance for water splitting.However,high cost and resource rarity of noble metal-base catalysts limit their utilization,so the researchers turn their attention to transition metal compounds.The structure and morphology of transition metal compounds are improved and reconstructed by scientific design and effective experiments,which increase the number of catalytic active sites and reduce the catalytic resistance,thereby making it is easier to combine with water molecules and keeping their long-term catalytic performance.Thus,the catalysts of transition metal are widely believed to replace noble metals,which can be used in practical electrocatalytic water splitting.In this paper,it is introduced that how to improve catalytic performance of transition metal compounds for water splitting by using scientific design and effective experiments.The main contents are as follows:1.Development of highly efficient and stable bi-functional catalysts for hydrogen evolution（HER）and oxygen evolution reaction（OER）is important for the practical applicationofwatersplittingtechnologies.Herein,heterostructured Co（CO3）0.5（OH）·0.11H2O@CoSe nanowires arrays supported on nickel foam（CCH@CoSe/NF）are successfully synthesized using a simple and facile two-step hydrothermal method as efficient bi-functional catalysts for overall water splitting in alkaline media.The optimized CCH@CoSe/NF catalytic electrode exhibits excellent OER activity with low overpotentials of 255 mV at 10 mA cm^-2 and superior stability after 1000CV cycles and 12 hours as well as HER activity with low overpotential of 128 mV at 10mA cm^-22 and superior stability after 1000 CV cycles.The defect-rich heterojunction structure of the catalyst and the NF substrate were helpful to enhance the catalytic activity of catalyst and the electron migration ability.Significantly,the cell based on bi-functional CCH@CoSe/NF//CCH@CoSe/NF couple showed highly efficient overall water electrolysis with low potential of 1.638 V at 10 mA cm^-2 in an alkaline electrolyte and maintained a good stability,indicating that the as-prepared material hides huge potential in actual overall water splitting electrocatalysis.2.It is important way to study catalyst of anodic reaction for accelerating the rate of HER reaction and reducing the energy consumption of anodic reaction.The Ni doped Co9Se8 nanosheets on the nickel foam（Ni doped Co9Se8）are successfully synthesized for OER by simple two-step solvothermal method.The Ni doped Co9Se8 catalyst show good activity with low overpotential of 277 mV at 10 mA cm^-2 and 360 mV at 100 mA cm^-2 for OER in 1 M KOH resolution.And Tafel slop of Ni doped Co9Se8 catalyst is just 83.8 mV dec^-1.Moreover,the Ni doped Co9Se8 catalyst remains excellent stability at 20 mA cm^-2 for30 hours in alkaline resolution.compare to non-doped Co9Se8,Ni doping Co9Se8 nanosheet expand electrochemical specific surface areas and increase number of active sites,demonstrate Ni doped Co9Se8 have high-efficiency performance for OER.3.Exploitation of efficient and highly stable catalytic performance for bi-functional catalysts is important part for the practical water splitting.Herein,the Co3O4@Ni3Se4 core-shell nanorod arrays on the nickel foam（Co3O4@Ni3Se4/NF）are successfully synthesized as long-term and efficient bi-functional catalysts for water splitting in 1.0 M KOH.The satisfactory Co3O4@Ni3Se4/NF catalyst exhibits excellent activity with low overpotentials of 260 mV and 180 mV at 10 mA cm^-2 for OER and HER,respectively.And its overpotential is only higher than the initial overpotential within 10 mV when the Co3O4@Ni3Se4/NF has been used after 30 hours at OER and HER.Significantly,the cell based on bi-functional Co3O4@Ni3Se4/NF||Co3O4@Ni3Se4/NF couple showed low potential of 1.735 V at 10 mA cm^-2 in alkaline electrolyte and remains a current density of 10 mA cm^-2 for 30 hours without serious attenuation,indicating that the as-prepared catalyst hides huge potential in practical water splitting.