Preparation And Oxygen Evolution Reaction Performance Of Self-Supported Nickel Selenide-Based Electrocatalysts

As a new clean energy,hydrogen energy is expected to replace the fossil fuels.Thus,there is a lot of scientific interest in the creation of H₂.Water electrolysis is a clean and effective hydrogen production technology,which only uses water and electricity as sources.Generally,oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）are two processes of the water splitting,but the dynamics of OER process is slow and the overpotential is much larger because of the four-electron transfer reaction.Therefore,efficient catalysts are needed to accelerate the reaction.Precious metal catalysts are currently used,but face high price,resource scarcity,and relatively poor stability,preventing their application in general.Consequently,the creations of efficient non-precious metal OER catalysts are essential.In this paper,many nickel selenide-based electrocatalysts with high activity were prepared by using nickel foam as substrate.Systematically discussed the relationship between the materials’structure and performance in OER.There are three parts to the paper’s primary research:1.Preparation of nickel selenide nanosheets supported on nickel foam for oxygen evolution reactionA series of nickel selenide nanosheets supported on nickel foam（NiSe₂/NF）were synthesized by direct selenization of the pretreated nickel foam substrate in N₂atmosphere.The spontaneous redox reaction between Ni and Se is advantageous for the formation of NiSe₂.The effects of selenization temperature,selenium content,and calcination time on the OER performance were systematically investigated,and the optimal catalyst was selected.The results show that when the selenization temperature is350℃,the mass ratio of nickel foam to selenium powder is 1:2,and the constant calcination time is 2 h,the best OER performance would be seen in NiSe₂/NF.The overpotential is 458 m V at 100 m A cm^-2,and it can be sustained for up to 36 h.The excellent OER performance of NiSe₂/NF is probably attributed to the reason that the composition of nickel foam and NiSe₂ contributes to a large specific surface area and good conductivity,which accelerates the rapid transfer of charge.Meanwhile,the higher Se atomic density in NiSe₂ implies a stronger electronegative surrounding,resulting in the Ni²⁺shell electrons are more readily drawn to the Se atom.,thus it has excellent OER performance.2.Preparation of nickel-cobalt selenide nanomaterials supported on nickel foam for oxygen evolution reactionNickel-cobalt selenide nanocomposite supported on nickel foam（NiSe₂-CoSe/NF）was prepared by a hydrothermal-calcination method on nickel foam substrate,and used as OER catalyst in an alkaline electrolyte.The effects of selenization temperature and nickel-cobalt ratio on OER performance were investigated.It was found that the best OER activity was obtained under the conditions of 350℃selenization temperature and 1:1nickel-cobalt ratio.The overpotential is 291 m V at 50 m A cm^-2.The OER performances of optimal bimetallic selenide catalyst are better than that of single metallic selenide,which may be due to the interaction between bimetallic selenides and nickel foam to endow the catalyst with a large surface area and good electrical conductivity.3.Preparation of nickel-iron selenide nanomaterials supported on nickel foam for oxygen evolution reactionNickel foam-supported nickel-iron selenide nanocomposite（NiSe-FeSe₂/NF）was prepared by hydrothermal coupled with calcination method,and used as OER electrocatalyst in an alkaline medium.The influences of selenization temperature and nickel-iron ratio on OER performance were investigated in detail.It was found that the best OER activity was obtained when the selenization temperature was 400℃and the nickel-iron ratio was 1:1.The overpotential at 100 m A cm^-2 is only 372 m V,and the current density(100 m A cm^-2)can be maintained for up to 63 h without a significant decrease.The bimetallic selenide catalyst also shows a better OER performance than that of single metallic selenide,and the reason could be attributed to the synergistic effect between bimetallic selenides and nickel foam,which can accelerate electron transport and improve the activity and stability of the electrocatalyst.