Preparation And Hydrogen Evolution Performance Of Electrodeposited Iron Rare Earth Electrode In Choline Chloride-urea System

The rapid consumption of fossil fuels and the growing ecological pollution problem make the development of new energy sources an urgent challenge.As a green and clean fuel,hydrogen energy is expected to become an alternative energy source to traditional fossil fuels.Alkaline electrolytic water is considered as one of the most sustainable methods for hydrogen production due to its safe production,stable yield and high product purity.Currently,the better performing catalysts for hydrogen precipitation are noble metal-based materials such as Pt and Pd.The intrinsic catalytic activity of these materials is more desirable,but their high production cost and small reserves prevent their widespread use and limit their development potential.Studies have shown that transition metal-based catalysts（Ni,Co,Fe,etc.）are the most promising materials to replace noble metal catalysts.In order to improve the performance of hydrogen precipitation catalysts,researchers have used various physical and chemical methods to prepare catalytic electrodes with larger specific surface area,more active sites and better electrical conductivity.Among these methods,alloyed electrodes are often used to improve and optimize the electrochemical properties of catalysts.The synergy existing between non-precious metal alloys can effectively modulate the electronic structure between the elements.Meanwhile,rare-earth materials have received a lot of attention from researchers for their application in electrocatalytic materials due to their unique electronic structures.In this paper,a high catalytic activity ternary iron system rare earth alloy electrode Ni-Fe-Sm/Cu was prepared by potentiostatic electrodeposition in choline chloride and urea ion system.When samarium chloride concentration is 0.04 mol·L^-1,deposition potential is﹣1.22 V,and deposition time is 20 min,the obtained Ni-Fe-Sm/Cu electrode material shows good electrocatalytic performance in alkaline solution.At 10m A·cm^-2,the overpotential of Ni-Fe-Sm/Cu is 115 m V and the tafel slope is 64 m V·dec^-1.Meanwhile,the Ni-Fe-Sm/Cu alloy electrode maintained good catalytic hydrogen precipitation activity after 1000 cyclic voltammetric curve（CV）scans in alkaline solution.In this paper,choline chloride-urea ionic liquid was chosen as the electrolyte to prepare ternary iron-based rare earth alloy electrodes on nickel foam（NF）substrate.The effects of different rare earth elements on hydrogen evolution properties of Co-Fe alloys were studied.Firstly,the optimal conditions of hydrogen evolution with different concentration ratios of Co-Fe were determined.On this basis,the Co-Fe-Sm/NF electrode prepared by adding Er,Nd and Sm showed the best catalytic activity.The Co-Fe-Sm/NF electrode showed a low overpotential(η₁₀=79 m V)and a low Tafel slope(62 m V·dec^-1)in alkaline medium.The Co-Fe-Sm/NF electrode showed excellent stability of hydrogen evolution and could be electrolyzed continuously for 12 h in 1.0mol·L^-1KOH alkaline solution.In conclusion,this study further enriches the understanding of adding rare earth elements to the choline-urea chloride system to improve the catalytic performance of hydrogen precipitation at Fe-based alloy electrodes and reveals that rare earth metal doping can be extended to other non-precious metal catalysts as a general method.