Fabrication And Hydrogen Evolution Performance Of Highly Active Molybdenum-sulfide-based Electrocatalysts

Molybdenum sulfide(MoSx),an earth-abundant and high activity material,appears to be an alternative to noble metal electrocatalysts in the hydrogen evolution reaction(HER).Herein,I first studied the correlation between the Mo/S ratio of MoS2 and the catalytic activity towards HER by using density functional theory(DFT).And then,I fabricated highly active MoSx electrocatalysts through several methods,including heating reduction method,ball-milling method and arcmelting technique.The main contents of this thesis are as follows:1.DFT calculations are applied to show that the influence of the Mo/S ratio on the electronic structure of MoS2 and the HER activity.When Mo:S=1:1.81-1:1.75,the hydrogen adsorption free energy of MoS2 is the lowest.2.A highly active MoS2-x electrocatalyst(H-MoS2)was prepared through heating reduction method.The H-MoS2 catalysts show enhanced catalytic activity for HER.We also studied the effect of reaction time to the catalytic performance of the catalysts.The results show that the H-MoS2 heated for 4 h exhibit better HER catalytic activity in both acidic and alkaline electrolytes,of which the S/Mo ratio is equal to 1.79.3.An efficient and straightforward ball milling method is highlighted to fabricate a highly active MoSx catalyst(DR-MoS2),of which the S/Mo ratio is equal to 1.80.DR-MoS2 exhibits obviously improved HER activity with an overpotential(at 10 mA cm-2)of 176 mV in acidic media and 189 mV in basic media.4.A highly active molybdenum multisulfide(MoSx)hybrid material,of which the S/Mo ratio is equal to 1.45,was prepared by an arc-melting method,which exhibits superior activity in acid media with a low overpotential of 156 mV at j=10 mA cm-2,surpassing most of existing molybdenum-sulfide-based catalysts.In summary,DFT calculation results show that the HER performance of MoS2 can be controlled with Mo/S ratio.And then,I fabricated highly active MoS2 electrocatalysts through several methods,including heating reduction method,ballmilling method and arc-melting technique.And all these materials exhibit significantly enhanced catalytic activity for HER.