All-in-one surface engineering strategy on nickel phosphide arrays towards a robust electrocatalyst for hydrogen evolution reaction

Efficient hydrogen evolution reaction electrocatalysts based on inexpensive and earth-abundant elements could enable low-cost water splitting and H-2 production, thus are compelling for the conversion of renewable electricity to fuels. In this work, we showcase the combinations of multiple surface engineering routes in a Ni2P electrocatalyst that achieves significantly enhanced catalytic performance. The surface roughness and structure disordering of the Ni2P arrays on carbon foil are precisely regulated by altering the annealing condition, resulting in a surface area-enlarged, defect-rich and superaerophobic catalytic surface. Density functional theory calculations are used to identify the effect of defective sites on the free energy for hydrogen adsorption in hydrogen evolution. Meanwhile, the superaerophobic surface is proved to accelerate removing gas bubbles on the electrode, thus facilitate the catalytic process. In addition, the enlarged surface area of material is considered to elevate the catalytic performance by providing more active sites in reaction. The designed catalyst obtained through a moderate treatment exhibits optimal electrocatalytic activity in acidic media: a low overpotential of 63 mV at 10 mA cm(-2), small Tafel slope of 67 mV dec(-1) and outstanding stability over 10 h. The synthetic strategy shows great promise to design efficient catalysts via subtle surface engineering.