The mechanism and surface engineering of carbon encapsulate defects-rich molybdenum phosphide for the hydrogen evolution reaction in alkaline media.

Inexpensive metal-based electrocatalyst with excellent stability and activity for efficient hydrogen evolution reaction is the most critical issue for large-scaled water splitting. However, the electricity kinetics in alkaline is relatively sluggish than in acid owing to the concentration of protons in alkaline is low. Thus, accurate structural designs to obtain more protons in the water dissociation on the surface of catalyst are necessary. In this work, a defect-rich MoP is encapsulated with carbon shell, which precisely regulated to distinguish the affection on hydrogen evolution reaction. The synergistic effect between carbon shell and defective sites is identified by the free energy and charge distribution density for water/hydrogen adsorption in hydrogen evolution via a density functional theory calculation. The results show that the lattice defects and the carbon shells play a unique role in enhancing catalytic performance, which the lattice defects decide the active sites and the thinner carbon shell would enhance its activity. The optimal overpotential in alkaline media of this designed MoP/C is 100 mV at 10 mA cm−2, its Tafel slope is 67.4 mV dec−1, and also exhibits a long-term stability for 12 h. • Structure disordering and carbon shell on MoP precisely regulated. • Low onset overpotential (30 mV), small Tafel slope (67.4 mV·dec−1) can achieved in alkaline media. • Synergistic effect between lattice defects and carbon shell are considered to enhance HER catalytic performance. [ABSTRACT FROM AUTHOR]