Structural Engineering of Highly Accessible Edge Sites and Electronic Optimization of N-MoS_2 for Efficient Hydrogen Evolution

摘要

Superior HER performance of MoS_2 electrocatalyst has been demonstrated due to the low free energy of hydrogen adsorption, electrochemical stability and cost-effectiveness. However, experimental and theoretical studies reveal that the HER activity of MoS_2 remains unsatisfactory due to the inactive basal planes, low intrinsic electronic conductivity and restacking of 2D layered nanosheets. To overcome these challenges, maximizing the accessible active sites and enhancing the conductivity of MoS_2 are critical to boost its HER performance. Herein, we perform structural engineering of MoS_2 electrocatalyst by developing a self-template strategy realizing a "0D/3D" nanostructure of N-doped MoS_2 nanocrystals anchored on carbon network (N-MoS_2/CN). As-prepared N-MoS_2/CN could address the above-mentioned issues: 1) N dopants in MoS_2 could simultaneously boost HER activity of the edge and enhance electronic conductivity of the basal plane; 2) The ultrasmall size of N-MoS_2 nanocrystals largely enriches the density of active edge sites; 3) The 3D hierarchically porous structure of the carbon substrate delivers the accessibility of H_3O~+ ions from electrolyte to active sites on MoS_2 and also facilitates the charge transfer during the HER process. Consequently, N-MoS_2/CN exhibits an onset potential of -30 mV vs. RHE, an overpotential of 114 mV at a current density of 10 mA cm~(-2) and a Tafel slope of 46.8 mV dec~(-1), demonstrating one of the best HER performance among various nanostructured MoS_2 electrocatalysts.