Cation vacancy modulated CuP-CoP heterostructure electrocatalyst for boosting hydrogen evolution at high current densities and coupling Zn-HO battery.

Exploiting highly efficient, cost-effective and stable electrocatalysts is key to decreasing hydrogen evolution reaction (HER) kinetics energy barrier. Herein, the alkaline HER kinetics energy barrier can greatly reduce by the joint strategies of the cation vacancy and heterostructure engineering, which is seldom explored and remains ambiguous. In this study, an efficient and stable copper foam-supported CuP-CoP heterostructure electrocatalyst with cation vacancy defects (defined as CuP-CoP-V/CF) was designed for HER via the successive coprecipitation, electrodeposition, alkali etching and phosphorization treatments. As anticipated, the as-obtained CuP-CoP-V/CF electrocatalyst reveals a remarkable catalytic activity for HER with a low overpotential of 205 mV at a current density of 100 mA·cm, a high turnover frequency value of 1.05 s at an overpotential of 200 mV and a small apparent activation energy (E) of 9 kJ·mol, while shows superior long-term stability at large current densities of 100 and 240 mA·cm. Systematic experiment and characterization data demonstrate that the formed cation vacancy could optimize the E, leading to the decrease of the kinetic barriers of CuP-CoP/CF heterostructure, as well as the established heterogeneous interface induced a synergistic effect between biphasic components on boosting the kinetics toward HER. The results of density functional theory disclose that the synergistic effect of CuP-CoP heterostructure could decrease the energy barrier and optimize Gibbs free energy of hydrogen adsorption, resulting in the enhancement of intrinsic catalytic activity of CuP-CoP-V/CF. More significantly, the alkali-cell assembled by CuP-CoP-V/CF (cathode) and RuO/CF (anode) behaves outstanding water splitting performance, delivering a current density of 10 mA·cm at a relatively small applied voltage of 1.58 V, along with encouraging long-term durability. In addition, the alkaline Zn-HO battery with CuP-CoP-V/CF as the cathode has been fabricated for the simultaneous generation of electricity and hydrogen, which displays a large power density of up to 4.1 mW·cm. The work demonstrates that rational strategy for the design of competent electrocatalysts can effectively accelerate the kinetics of HER, which supplies valuable insights for practical applications in overall water splitting.