Design And Construction Of Molybdenum Carbide Based Electrocatalyts And Their Hydrogen Evolution Reaction Perormance

Nowadays,with environment and energy problems increasing,reducing the dependence on fossil fuels draws many attentions.Many new energy technolgoies have been explored in order to solve these issues.Rechargeable batteries like Li-battery and hydrogen based devices like LTFC?low temperature fuel cell?are two of the most promising and highlighted alternatives to traditional fossil fuels.Among the hydrogen generation methods,electrochemical water splitting is one of the most environmentally sustainable way.Hydrogen evolution reaction?HER?for water splitting basically depends on electrocatalysts which must possess low dynamic overpotential.Up to now,noble metals such as platinum?Pt?and its alloys are still the most active electrocatalysts for HER.However,their low abundance and high cost have severely limited their scale-up applications.Therefore,in the future it is essential to explore noble-metal-free electrocatalysts to replace Pt-based electrocatalysts.In the first research work of this thesis,the author applied polystyrene?PS?as hard template and polymerized a layer of polyaniline outside the PS to form a special SPS@PANI precursor.Then due to the chelation effect between polyaniline and Molybdenum acid radical,SPS@PANI-Mo was produced,after carbonization under inert atmosphere in tube furnace,the final catalyst formed a hollow sphere structure,consisting of both Mo₂C and Mo₂N active nanoparticles embedded in N-doped carbon?N-C?framework.Herein,the shrunken hollow spherestructure is of benefit to increasing active site density of Mo based catalysts,and the N-C encapsulated surface can shield the internal Mo active sites and further strengthen the electron conductivity and activity,available to enhance the electrocatalytic performance.In terms of this novel strategy,Mo₂N and Mo₂C dual-active sites generate a synergistic effect by changing the electron configurations,thereby lowering the overpotential of hydrogen generation.This experiment discussed the synergistic effect between Mo₂N and Mo₂C and offered a strategy further design of high performance HER catalyst.The second research work of this paper synthesized a uniform hollow Mo₂C nanosphere structure with a facile method.Specifically,we combined interfacial polymerization and chelation effect by using one-step method to synthesize the Mo-polydopamine precursor.By adjusting the additive amount of dopamine-HCl and keeping other conditions consistent,different scales of cavities in Mo–PDA hollow spheres are obtained then we proved the hollow cavity can boost the HER performance through our following tests.The result shows the Mo₂C@C-3 only requires an overpotential of 135 mV to reach a current density of 10 mA cm^-2 and under a current density of 50 mA cm^-2,the overpotential can be controlled in 200 mV.Besides,the Mo₂C@C-3 also exhibits outstanding stability under extensive HER tests.