Hierarchical Ultrathin Mo/MoS2(1- x - y ) Px Nanosheets Assembled on P, N Co-Doped Carbon Nanotubes for Hydrogen Evolution in Both Acidic and Alkaline Electrolytes.

ABSTRACT

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/MoS2(1- x - y ) Px nanosheets composites (Mo/MoS2(1- x - y ) Px @PNC) for hydrogen evolution reactions (HER). The PNC guarantees structural stability and fast charge transfer in a long-range, while Mo/MoS2(1- x - y ) Px 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/MoS1.15 P0.30 @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 H2 SO4 and 1.0 m KOH, respectively. Density functional theory calculations confirm that the higher substitution of S atoms by P in MoS2 can form strong Mo 3d-S 2p-P 2p hybridizations at Fermi level, resulting in the narrower bandgap and smaller ∆GH * of hydrogen (H*) adsorption, thereby leading to the promoted HER activity.