Study On High Efficiency Hydrigen Evolution Performance Of Self-supported Transition Metal Matrix Composites

Hydrogen energy is an excellent alternative to fossil fuels because of its clean,efficient,and recyclable properties.Compared with many existing hydrogen production processes,electrolytic water hydrogen production has the characteristics of being green,simple,and efficient.As the core of hydrogen production from electrolytic water,the catalyst seriously affects hydrogen production efficiency.The noble metal catalyst has the best effect,but its high material cost and resource scarcity limit its wide application,so the research on non-noble metal-based electrocatalysts has become the current mainstream development direction.The synergies between multiple transition metal compounds can significantly improve the catalyst’s performance compared to the mono-metal catalyst,thus optimizing the catalytic process of hydrogen evolution reaction（HER）.This paper prepares self-supporting composite materials with excellent catalytic performance,high conductivity,and high stability by loading transition metal compounds onto a self-supporting conductive substrate.With the help of various characterization methods and electrochemical testing techniques,the prepared materials composition,structural morphology,and electrochemical performance are explored.The structure-activity relationship between catalyst morphology and catalyst performance was studied as follows:Firstly,an electrochemical redox technology constructed an array of copper nanowires on the surface of the copper foam.Then Co Ni-LDH nanosheets were in-situ grown on the array of copper nanowires by electrochemical deposition technology and phosphating in one step.Co P-Co₂P-Ni₂P/Cu NWs supported on copper nanowires were prepared.The array structure of copper nanowires increases the specific surface area of copper foam,increases the load of cobalt-nickel active material,and realizes rapid and stable electron conduction.By constructing the catalyst morphology of cobalt-nickel phosphide heterogeneous nanosheets,more cobalt-nickel active sites were exposed.The electronic structure of the interface of cobalt-nickel nanosheets was effectively regulated by controlling the phosphating degree,and the catalytic activity of the self-supported catalyst was effectively improved.The prepared Co P-Co₂P-Ni₂P/Cu NWs self-supported catalyst showed excellent HER electrocatalytic activity and stability.In an alkaline medium,the overpotential is 28 m V at 10 m A cm^-2 current density.When the current density increases to 100 m A cm^-2,the overpotential is only 153 m V.In addition,the Co P-Co₂P-Ni₂P/Cu NWs catalyst exhibited a Tafel slope of 82.1 m V dec^-1,stable for 70 h at a current density of 45 m A cm^-2.Considering the simplicity,expansibility and excellent catalytic performance of the synthesis method,this study opens up a new way to design a new type of low cost and high performance electrocatalyst.Secondly,Crystalline nickel-cobalt-iron phosphide nanoparticles（NiCoP@NiCoFeP/NF）were in-situ grown on amorphous cobalt-nickel phosphide nanoarrays supported by nickel foam by electrochemical deposition,liquid-phase growth,and phosphating.Ni Co-LDH was modified onto the surface of the nickel foam skeleton by electrochemical deposition,which increased the specific surface area of the nickel foam and provided more nucleation sites for subsequent reactions.Then,the Prussian blue analogue（NiCoFe-PBA）of nickel-cobalt iron（NiCoFe-PBA）was formed on the surface of Ni Co-LDH using cobalt-nickel on Ni Co-LDH as a carrier by coordination with potassium ferricyanide.Finally,NiCoP@NiCoFeP/NF was obtained by the phosphating reaction.When the current density reaches 100 m A cm^-2 in 1 M KOH solution,hydrogen evolution overpotential is only 139 m V,and the low Tafil slope of59.6 m V dec^-1 is shown.NiCoP@NiCoFeP/NF electrocatalyst can run for 72 h at 60 m A cm^-2 current density,showing excellent electrocatalytic stability.In addition,the multistage three-dimensional network structure of Ni Co-LDH and NiCoFe-PBA significantly improves the active specific surface area of the self-supported catalyst,enhances the stability of the catalyst,and improves the electrocatalytic hydrogen evolution performance of the catalyst.This study provides an attempt for the design and synthesis of novel nanostructured electrocatalysts,and provides some enlightenment for the design of efficient,stable and low-cost HER electrocatalysts.