Preparation Of Mo₂C@C Composites And Their Electrocatalytic Hydrogen Evolution Properties

The development of environmentally friendly energy conversion technology is an effective strategy to solve the problems of energy crisis and environmental pollution caused by fossil fuel combustion.In recent years,the widely studied electrolysis of water to hydrogen production technology is an effective method to convert electrical energy into chemical energy.The focus of this technology is to develop corresponding electrocatalysts to reduce the electrochemical reaction barrier and promote the electrochemical reaction kinetics.Mo₂C has been extensively studied for its platinum-like d-band electronic structure,and great progress has been made in the field of energy conversion and storage.However,Mo₂C still has the disadvantages of high Mo-H bond strength and easy sintering at high temperature.Biomass are environmentally friendly and rich in resources,and contain a large number of non-carbon atoms.Biomass-derived carbon can be used as a carbon skeleton to disperse molybdenum carbide,and non-carbon atoms make heteroatom doping possible,thereby further improving its electrocatalytic performance.In this paper,chitin and adenine were used as carbon and nitrogen sources to prepare Mo₂C/nitrogen-doped carbon composites,and the electrocatalytic hydrogen evolution performance of Mo₂C was optimized by regulating the morphology and structure,combining with carbon matrix,and nitrogen doping.The main research contents are as follows:（1）Using chitin as carbon source and nitrogen source,Mo₂C precursors were prepared by acid induction strategy,and nitrogen-doped Mo₂C@CN composites with different particle sizes were obtained after carbonization.The particle size of the product changes with the amount of HCl added in the preparation,which affects the electrocatalytic hydrogen evolution performance.The doping of N tunes the electronic state of the Mo and C atoms and weakens the binding strength of Mo-H.When 1 m L of HCl was added,the prepared material possesses the best catalytic performance with an overpotential of 168 mV and a Tafel slope of 62.68 mV dec^-1 at a current density of 10m A cm^-2.（2）With adenine as carbon and nitrogen sources,the morphology of Mo₂C was regulated by the introduction of different surfactants such as sodium lauryl sulfate（SDS）,cetyltrimethylammonium bromide（CTAB）,sodium dodecyl benzenesulfonate（SDBS）and stearic acid（SA）.The influence of different hydrothermal time and carbonization temperature on the formation of Mo₂C was also explored.When the surfactant SDS was added,the hydrothermal time was 24 h,and the carbonization temperature was 700°C,the prepared Mo₂C exhibits the best catalytic performance.The overpotential can reach 145 m V when the current density is 10 mA cm^-2,and the Tafel slope is 62.48 m V dec^-1.（3）Using chitin as the carbon source and sodium bicarbonate as the pore-forming agent,N-doped porous carbon（NC）was obtained by high-temperature calcination.Mo₂C/N doped porous carbon composites was finally formed by hydrothermal reaction of the N-doped porous carbon with ammonium molybdate and recalcination process.The effects of SDS anionic surfactant and CTAB cationic surfactant on the structure and properties of the composites were explored.Among all the products,Mo₂C@NC-CTAB presents the best catalytic performance,with an overpotential of 236 m V at a current density of 10 mA cm^-2 and a Tafel slope of 75.14 mV dec^-1.