Hierarchical Ultrathin Mo/MoS_(2(1-x-y))P_x Nanosheets Assembled on P, N Co-Doped Carbon Nanotubes for Hydrogen Evolution in Both Acidic and Alkaline Electrolytes

摘要

Synergistically coupled 1D/2D materials have great potential for energy conversion application due to its high catalytic activity. Herein, an in situ assembly strategy is developed for preparing the P, N co-doped carbon nanotubes and Mo/MoS_(2(1-x-y))P_x nanosheets composites (Mo/MoS_(2(1-x-y))P_x@PNC) for hydrogen evolution reactions (HER). The PNC guarantees structural stability and fast charge transfer in a long-range, while Mo/MoS_(2(1-x-y))P_x nanosheets offer a large electrochemically active surface area with embedded metallic Mo in improving its internal conductivity and rich surface/interface properties. Thus, the optimized catalyst (Mo/MoS_(1.15)P_(0.30)@PNC) possesses more surface active sites and exhibits extraordinary HER activities, with a small overpotential of -79 and -131 mV at 10 mA cm~(-1), and low Tafel slope of 49 and 82 mV dec~(-1) in 0.5 m H_2SO_4 and 1.0 m KOH, respectively. Density functional theory calculations confirm that the higher substitution of S atoms by P in MoS_2 can form strong Mo 3d-S 2p-P 2p hybridizations at Fermi level, resulting in the narrower bandgap and smaller ΔG_(H*) of hydrogen (H*) adsorption, thereby leading to the promoted HER activity.