Preparation Of Aluminum And Cobalt Modified MoS₂/rGO Electrocatalysts And Their Hydrogen Evolution Performance

Hydrogen energy is a green and clean energy source that has become one of the most promising energy sources for humans.Hydrogen production via water electrolysis has the advantages of high conversion efficiency,high product purity,and environmental friendliness,making it a hot research topic.However,the current industrial technology for hydrogen production via water electrolysis has the problems of high cost and high energy consumption,which can not meet the needs of sustainable development.Therefore,this paper aims to obtain a MoS₂-based catalyst with high-efficiency electrocatalytic hydrogen evolution activity through active site design,phase regulation,and structure optimization,and explore its hydrogen production performance and uranium extraction ability in seawater,providing theoretical basis for the development and expansion of hydrogen production technology via water electrolysis.Al-modified MoS₂ catalysts were prepared by both atomic layer deposition and high-energy ball milling methods,and XRD and SEM were used to study the composition and structure of the Al-MoS₂ catalysts,and the effect of the preparation method on the crystalline phase of the catalyst was explored.Electrochemical testing methods were used to study the electrocatalytic hydrogen evolution performance,and the mechanism of Al modification to enhance the electrocatalytic hydrogen evolutionactivity of MoS₂ was explored using DFT calculations.The results show that in the Al-1T-MoS₂ catalyst prepared using high-energy ball milling method has the overpotential of 196 m V at current density of 10 m A cm^-2,lower than Al-MoS₂ catalyst prepared using atomic layer deposition method of 207 m V and 2H-MoS₂ catalyst of 294 m V.The introduction of Al weakens the adsorption of H on S active site.Al-1T-MoS₂ has ample edge structures,providing abundant exposed active sites.Moreover,the transformation to 1T from 2H phase promotes the conductivity of MoS₂.Therefore,the hydrogen evolution activity can be significantly improved.Al and Co-modified 1T-MoS₂ electrocatalyst was prepared using high-energy ball milling method and further constructed a 3D structure by combining with reduced graphene oxides.The effects of cobalt content and ball milling speed on the chemical composition,structure,and electrocatalytic hydrogen evolution performance of the catalyst were studied through XRD,SEM,and electrochemical tests,and the mechanism of Co improving the hydrogen evolution activity of MoS₂catalyst was revealed by DFT calculations.The results showed that when the cobalt content was 10 wt%and the ball milling speed was 700 rpm,the Al and Co-modified1T-MoS₂ catalyst had the highest electrochemical hydrogen evolution performance on 1T-MoS₂ with the overpotential of 102 m V at a current density of 10 m A cm^-2.The Co atom modified on MoS₂ as the hydrogen evolution site has a lower water dissociation energy and moderate hydrogen adsorption free energy,enhancing the electrocatalytic hydrogen evolution activity of MoS₂-based catalysts.The three-dimensional catalyst exhibits much bigger special surface areas and electrochemical active surface areas to boost the electrocatalytic hydrogen evolution performance and the overpotential was decreased to 89 m V at a current density of 10 m A cm^-2.The hydrogen evolution performances in seawater of Al and Co-modified 1T-MoS₂/rGO catalyst were studied,and it was found that the extraction of uranium could be achieved simultaneously with the hydrogen evolution in seawater.The influence of seawater environment on the electrocatalytic hydrogen evolution was revealed and synergistic mechanisms for hydrogen evolution and uranium extraction was explored.The results showed that the product of hydrogen evolution,hydroxyl ions,could form high polymers with uranyl ions in the seawater,simutaneously boosting the performances of electrochemical hydrogen evolution and uranium extraction.The hydrogen evolution overpotential of Al and Co-modified 1T-MoS₂/rGO catalyst in the simulated seawater was 465 m V.It can be decreased by21 m V in the presence of uranyl ions with the concentration of 100 mg L^-1.This is ascribed to that the formation of high polymers between uranyl ions and hydroxyl ions could shift the equlibrium of hydrogen evolution reaction to the product direction,boosting hydrogen evolution performance.When the voltage was-1.2 V and extraction time was 1 h,the Al and Co-modified 1T-MoS₂/rGO catalyst had a uranium extraction capacity of up to 1990 mg g^-1 and nearly 100%extraction rate.In addtion,it showed good cycling stability.The DFT calculation results showed that the Co sites undergo rapid hydrogen evolution reaction to produce a large amount of OH*.Simutaneously,the S atoms selectively adsorp uranyl ions and decrease the charge density of U atom,strengthening the binding of OH*with uranyl ions.This leads to the precipitate of UO₂（OH）₂,achieving high-efficiency uranium extraction.