Catalytic Performance Of Acetylene Black/Molybdenum Disulfide Composites For Hydrogen Evolution

Hydrogen（H₂）is considered as the most promising green and storable fuel.Producing hydrogen by water electrolysis has been extensively investigated.So far,the precious metal-based catalysts possess the lowest overpotential for hydrogen evolution reaction（HER）.However,the precious metal-based catalysts have some shortcomings,e.g.expensive price and weak cycling stability etc.Therefore,rationally designing high-performance non-precious metal-based catalysts has attracted much attention.The studies report that molybdenum disulfide（MoS₂）shows high catalytic HER activity,as well as poor electrical conductivity,weak cycling stability,and deficient active sites on the surface.The controllable morphology,electron modulation,and conducting composite materials are the most effective strategies for improving the catalytic performance of MoS₂.In this thesis,the HER activity of MoS₂ is promoted by incorporating conductive acetylene black（AB）and introducing the transition metal ions.Through a hydrothermal method,weakly oxidized AB/MoS₂ composite materials are prepared,Acetylene black can significantly improve the conductivity of MoS₂,and thus improve the catalytic performance of MoS₂.demonstrating desirable HER activity for the water electrolysis benefiting from enhancement of interfacial conductivity between AB and MoS₂ due to weakly oxidization treatment.The composites still have great potential for performance improvement.Subsequently,transition metal Co,Ni,and Fe ions are introduced into the AB/MoS₂ composite materials to optimize the performance.When introducing the Co ions,the composite materials are composed of triple-phase AB/Mo_1-xCo_xS₂/Co_1-yMo_yS₂.For the low content dopants,AB/Mo_1-xCo_xS₂ composite materials are obtained.The introduction of Co ions steers the electronic structure,leading to preferable free energy for H adsorption and promoting catalytic activity.The onset overpotential decreases with increasing the doping content.When reaching the doping fraction of 0.3,the onset overpotential is 107 m V for alkaline HER.The third phase(Co_1-yMo_yS₂)is formed as further increasing the doping content,giving rise to a negative impact on catalytic performance.Nevertheless,the cycling stability of composite materials is significantly improved.When introducing the Ni ions,the composite materials consist of triple-phase AB/Mo_1-xNi_xS₂/Ni_1-yMo_yS₂.The similar performance trend is identified to that of Co-doped catalysts.For the low doping content,the composite materials are AB/Mo_1-xNi_xS₂ and the catalytic performance is enhanced.When reaching the doping fraction of 0.2,the onset overpotential is 68 m V for alkaline HER.The third phase(Ni_1-yMo_yS₂)is formed as further increasing the doping content,while the performance is not improved.When introducing the Fe ions,the composite materials consist of triple-phase AB/Mo_1-xFe_xS₂/Fe_1-yMo_yS₂ with low x and y values.This is attributed to strong hydrolysis nature of Fe³⁺,resulting in the formation of stable Fe₂O₃ during the hydrothermal process.Small doping of Fe ions does not dramatically regulate the electronic structure of MoS₂,and massive non-conductive Fe₂O₃ causes reduced catalytic performance.It was found that doping transition metal ions into MoS₂ did not cause significant changes in specific surface area.As a catalyst,it is very important to improve the specific surface area and the amount of active sites.Therefore,in addition to doping,it is very important to study the synthesis method for the regulation of microstructure.