Preparation And Electrocatalytic Performance Of Mo₂C/NC Nanocomposites

Sustainable hydrogen production from electrocatalytic water splitting is a promising alternative to fossil fuels.Pt-based materials are considered as the most efficient and stable catalysts in HER,but their high cost has hindered the scale-up application in industry.Among these non-precious metal-based materials,molybdenum carbides have attracted intense attention in the field of electrocatalysis and heterogeneous catalysis.In this paper,Mo₂C/NC nanocomposite is synthesized and their electrocatalytic hydrogen evolution properties are studied.By simple coprecipitation process,aniline,benzylamine and o-toluidine were used as nitrogen-containing carbon sources,respectively,then hybridized with ammonium molybdate to carbonize at 800°C to obtain Mo₂C/NC-AN,Mo₂C/NC-BZA and Mo₂C/NC-OT.The results show that replacing the nitrogen-containing carbon source will change the microstructure and distribution of element valence state on the surface of the material,therefore influence the hydrogen evolution performance.The three materials were tested for hydrogen evolution in acidic and alkaline solutions.It is found that when the current density is-10 mA·cm^-2 in acidic solution,the overpotentials of Mo₂C/NC-AN,Mo₂C/NC-BZA and Mo₂C/NC-OT are 204,225 and 249 mV,respectively.The materials still have good stability after 11 h.To further improve the performance of Mo₂C/NC-AN,Mo₂C/NC-AN is optimized from three aspects:carbonization temperature,raw material ratio and carbonization process.It is concluded that when the molar ratio of molybdenum atom to aniline in ammonium molybdate is 3:1,and the precursor prepared at 800°C has the best catalytic hydrogen evolution performance.This paper used one-step and two-step carbonization method to carbonize the precursor to form a porous nanowire composite composed of?-Mo₂C and a nitrogen-doped carbon matrix.XRD,Raman,BET,XPS,SEM,TEM and other characterizations were used to reveal the important role of the two-step carbonization method in heteroatom-doped carbon materials.Compared with Mo₂C/NC-1,the two-step carbonization products?Mo₂C/NC-2?not only have higher Mo-C catalytic active sites on the surface,but also have stronger electronic interaction between Mo₂C and the carbon matrix.Therefore,Mo₂C/NC-2 has excellent properties in both acidic and alkaline solutions.As a consequence,Mo₂C/NC-2 provides a geometric catalytic current density of-10 mA·cm^-22 at overpotentials of 169 mV and180 mV?vs.RHE?in 0.5 M H₂SO₄ and 1 M KOH,respectively.