The Preparation Of Cobalt Selenide（Co₃Se₄）for Electrocatalystic Oxygen Evolution Reaction

For the scarcity of fossil fuels and global environmental pollution,hydrogen is an important clean energy in the future.In addition,electrochemical water splitting is the good method to produce hydrogen through renewable resources.At present,Hydrogen is the byproduct from oil,coal and natural gas during generating greenhouse gases.Although hydrogen-based fuel cells can be bought from supermarket,this energy still is produced by fossil fuels.Thus,it is necessary to develop a clean way to obtain hydrogen by renewable resources such as solar,wind,water and biomass energies.However,the sluggish kinetics of the oxygen evolution reaction（OER）would reduce the efficiency during water splitting.Ir/Ru-based oxides are the commercial catalysts for high OER performance and stability.But,the scarcity and expensive price limit the widespread application of these noble catalyst for energy conversion and storage.Thus,researchers have paid extensive efforts to develop non-noble catalysts for the OER.As a typical transition metal chalcogenide electrocatalyst,Cobalt selenide has attracted much attention of many researchers for its good electrocatalytic activity,chemical stability and conductivity.The electrocatalytic activity of cobalt selenide is mainly derived from the active sites on the surface of cobalt selenide.During hydrolysis reactions,Se/Co species can be combined with the intermediates to form appropriate chemical bonds.However,single cobalt selenide cannot used as commercial OER catalyst.Based on the analysis above-mentioned,this work made some modification for cobalt selenide.Through modifying and regulating the electronic structure of cobalt selenide,the catalyst showed good OER performance.In addition,we studied the catalytic reaction mechanism through in-situ Raman testing methods.The main content of this article includes the following parts.1.We reported an efficient Ni-doped rod-like Co₃Se₄hybridized with reduced graphene oxide（Ni-Co₃Se₄/rGO）as OER electrocatalyst by a two-step hydrothermal method.The doped Ni atom regulated the electronic structure of Co₃Se₄,significantly reducing the overpotential of Co₃Se₄toward OER in alkaline condition.In the meantime,the hybridization of reduced graphene oxide（rGO）enhanced the conductivity which benefited the improvement of OER activity.The Ni-Co₃Se₄/rGO catalyst shows a lower overpotential（284 m V at 10 m A/cm²）as well as a Tafel slope(71 m V dec^-1)which outperformed the benchmark of commercial Ru O₂.Moreover,the Ni-Co₃Se₄/rGO also shows high stability and long-term durability.Finally,In-situ Raman technic was used to explore the reaction mechanism of the catalyst.2.Chalcogenide compounds have good applications in OER.Sulfur atoms have a similar shell structure with selenium atoms.Therefore,based on the first work,we used sulfur and nickle atoms to dope in Co₃Se₄.the local electronic structure of Co₃Se₄were changed by the co-doped anion and cation.At the same time,reduced graphene oxide was used as a substrate to enhance the conductivity of the catalyst and accelerate electron transport to optimize the OER performance of Co₃Se₄.Finally,we used X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,cyclic voltammetry and linear scanning voltammetry to study the physical and electrochemical properties of the S,Ni-Co₃Se₄/rGO.In order to verify the effect of doping on the original material,we found that the OER performance of the co-doped material shows more excellent OER performance than any single material.3.Nickel sulfide nanoparticles supported by the bulk cobalt selenide were synthesized by hydrothermal methods as the electrocatalytic OER catalyst.Then,we used X-ray diffraction,transmission electron microscopy,X-ray photoelectron spectroscopy,cyclic voltammetry and linear scanning voltammetry to study the physical composition and electrochemical properties of the Co₃Se₄/Ni_0.96S phase.The catalyst shows an excellent OER activity and stability under alkaline conditions.In order to verify that the effect of support on original material,we prepared single Co₃Se₄and Ni_0.96S catalyst.Then,we found the composed material shows more excellent OER performance than any single material.