Synthesis Of Mo₂C（W₂C）-carbon Nanotubes Composite For Electrocatalytic Hydrogen Evolution Reaction

Transition metal carbides have attracted much attention in recent years as highquality catalytic materials.Because they have similar energy band structure as Pt,so they have many outstanding properties.Electrocatalytic hydrogen evolution performance is one of them.As a potential alternative to precious metals platinμm and palladiμm electrocatalysts,transition metal carbides have the advantages of high natural reserves,low cost,high catalytic activity,easy realization of industrial production,and the ability to solve the problem that precious metals platinμm as an electrocatalyst is difficult to spread.However,there are many kinds of transition metal carbides,so it is particularly important to select suitable transition metals for study,and molybdenμm and tungsten stand out from the many transition metals due to their low cost,high abundance,and valence of valence.The molybdenμm carbide and tungsten carbide derived from it have very outstanding electrocatalytic properties.In this project,the preparation of Mo2C(W2C)-carbon nanotubes composite was performed by simple in-situ carburization synthesis.Mo-PANI precursors were firstly synthesized by using ammoniμm molybdate tetrahydrate as the molybdenμm source.The Mo2C-carbon nanotubes composite named Mo2C/N-C(A)was prepared by carburizing.The tests about composition,structure and morphology of the composite shows that the material has pure phase β-Mo2C and is of hollow Tubular structure.It has the best performance at 800℃ after changing the carbonization temperature,and only 215 mV is required when the current density reaches 10 mA/cm2.After characterization by structure,composition and performance,it could be found that Mo2C-carbon nanotube composite — Mo2C/N-C(S)has more excellent hydrogen evolution performance,which is benefited by its good morphology,smaller Mo2 C nanoparticles(2~3 nm),larger specific surface area and more active sites.It only needs 188 mV can reach the current density of 10 mA/cm2,and the Tafel slope is only 58 mV/dec.Using the same method,the precursor of W-PANI was synthesized by using(NH4)6H2W12O40·XH2O and Na2WO4·2H2O as the tungsten source,The two W2 Ccarbon nanotube composite—W2C/N-C(A)and W2C/N-C(S)was obtained after carburizing under inert gas at 800℃.After XRD characterization,it was found that W2C/N-C(S)materials was only made up of the pure phase but W2C/N-C(A)materials has many heterogeneous phase.Through the electrochemical test comparison,materials of W2C/N-C(S)was proved to have better performance,and reaches the best under acidic conditions,then the carbonization temperature and W-C ratio was further explored and characterized some electrochemical tests.The results showed that it got the best performance at 800℃,an overpotential of 245 mV was required to reach a current density of 10 mA/cm2,and the Tafel slope was 73 mV/dec.and the best proportion of W:C goes to 2.0:3.0.Only an overpotential of 222 mV was needed to reach the current density of 10 mA/cm2,and the Tafel slope was 70 mV/dec.