Design And Property Studies Of Molybdenum Carbide-based Electrocatalytic Catalyst

Among many hydrogen production reactions,the electrolyzed hydrogen evolution reaction?HER?is considered to be one of the efficient,convenient,and green effective methods for preparing high-purity hydrogen.The development of new high-performance HER catalysts is the core task of this technology.Due to the special electronic structure on the molybdenum carbide surface,it is widely regarded as a catalyst with the potential to replace the current commercial Pt/C.However,the intrinsic activity of molybdenum carbide is still sluggish for HER.Therefore,modifying molybdenum carbide-based catalytic materials is an important method to improve its catalytic performance.In view of above problems,this paper starts from four aspects to improve the activity of catalysts:molybdenum carbide surface-loaded metal modification;vacancy-metal control Mo₂C surface electronic structure,and controlling morphology of Mo₂C.The above work is briefly as follows:?1?Influence of metals on the HER over molybdenum carbide:The organic-inorganic hybrid method and in-situ high-temperature carbonization method were used to synthesize highly dispersed molybdenum carbide supported metal M?2%M/Mo C,M=Fe,Co,Ni,Cu,Ag,Pt?catalyst.The characterization results show that the prepared catalyst sample display nanowires morphology,and composed with 3-10 nm Mo₂C nanoparticles.HER activity test shows that the overpotential of samples after metal loading is lower than?-Mo₂C and the 2%Pt/Mo₂C shows the optimal activity(?₁₀=79 m V),due to its higher BET specific surface area and more developed pore structure,faster electron transfer speed,and strong interaction with the carrier.?2?Influence of surface structure on the HER of the molybdenum carbide:The Co-Mo₂C nanosphere catalyst with heterogeneous structure was prepared by hydrothermal-high temperature carbonization method,after treating 12 hours in acid solution,a porous sample(Co₅₀-Mo₂C-12)was obtained.XPS and UPS results show that when Co atoms and Mo vacancies exist,electrons tuned to Mo atoms on the catalyst surface,resulting in increased the electron density near Mo Fermi level;DFT results further show the synergistic of the Co atoms and Mo vacancies effect significantly reduces the center value of the d-band on the Mo₂C surface,which reduces the Mo-H bond strength and increases the desorption ability to hydrogen.Co₅₀-Mo₂C-12 exhibits outstanding activity(?₁₀=125 m V)and stability.And the above synergistic effect is also applied to the molybdenum carbide-based catalyst with Mo vacancies on the surface modified by Fe and Ni.?3?Influence of shell-core morphology on the HER of the molybdenum carbide:Co_x@Mo₂C shell-core catalyst was prepared by hydrothermal-high temperature roasting.Characterization results shows the formation of Co_x@Mo₂C morphology is related to the Co content in catalysts:Co₅@Mo₂C nanospheres were interspersed by nanosheets;Co₁₀@Mo₂C nanospheres were interspersed by the nanoparticles;the surface of Co₅₀@Mo₂C nanospheres is smoothly with cores.Co₁₀@Mo₂C showed the outstanding activity in HER reaction,which related to the BET specific surface area and active site of the catalyst.