Preparation Of Nanostructured Carbon/Molybdenum Carbide Composites And Their Electrocatalytic Performance For Hydrogen Evolution

Electrocatalytic splitting water is one of most effective method forhydrogen production.Exploring efficient and cheap electrocatalysts to reduce energy consumption and improve the efficiency of hydrogen evolution reaction?HER?has attracted tremendous research interest.Molybdenum carbide has been exploited as one of the promsing HER electrocatalysts owing to their d-band states similar to platinum.However,the Mo₂C obtained at high temperature usually suffers the inevitable aggregation leading to the less exposure active sites,and the strong Mo-H binding strength restricts the desorption of adsorbed H?Hads?to generate H₂,thus compromising the HER performance.Therefore,molybdenumcarbidenanoparticles-coatedinto nitrogen-doped nanostructural carbon is designed as electrocatalysts for HER.The improved HER performance is believed to attribute to the synergetic function of suppresing particle agglomeration,enlarging the contact area between the electrolyte and the materials,exposing more active sites,and optimizing the electronic structure of molybdenum carbide.Alternatively,the relationship between the structure of presented materials and electrochemical performance is studied in detail.The specific contents are listed as followed:?1?The N-doped carbon nanofibers anchored molybdenum carbide nanoparticles are synthesized by electrospinning and annealing using polyacrylonitrile as carbon source and acetylacetone molybdenum as molybdenum source.The effects of electrospinning voltage,annealing temperature,the amount of ratio between cabon source and molybdenum source on the structure and morphology of the composites are investigated.Furthermore,the effects of structure and nitrogen doping of composite on its electrocatalytic hydrogen evolution performance is evaluated to reveal the key factors affecting electrocatalytic activity.The as-presented materials exhibit good HER performance.More importantly,molybdenum carbide/N-doped carbon nanofibers free-standing film used directly as electrocatalysts also shows excellent HER catalytic properties.?2?The molybdenum carbide nanoparticles-coated into the graphene wrapping N-doped porous carbon microspheres composite is prepared by spray-drying and annealing method.Exploring the key factors such as the amount ratio between ammonium molybdate and carbon source,spray drying parameters and annealing temperature regulates the morphology and structure of the composite.The HER performance of various materials obtained at different conditions are investigated in detail,and the relationship between microstructure and performance is estabished combining with the characterization and analysis of materials structure.The optimized material achieves a current density of 10 mA cm^-22 at very low overpotential?70 and 66 mV?and a smaller Tafel slope(39 and37 mV dec^-1)in acidic and alkaline electrolytes,respectively,indicating its excellent catalytic activity.