AlP-regulated phosphorus vacancies over Ni–P compounds promoting efficient and durable hydrogen generation in acidic media

Abstract

Engineered anion vacancy catalysts exhibit speedy activity in the field of electrocatalysis due to their tunable electronic structure and moderate free energy of adsorbed intermediates. Herein, we demonstrate a facile process of preparing multiphase phosphides with abundant phosphorus vacancies (P_V) supported on nanoporous Ni(Al). X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and high-resolution transmission electron microscopy (HRTEM) reveal that the as-obtained material has ample P_V induced by the AlP phase. The optimized catalyst also equips with aligned nanoflakes grown in situ on np-Ni(Al) skeletons/ligaments, thereby exposing a large specific surface area for hydrogen evolution reactions (HERs) in acidic media. Benefitting from its unique hierarchical structure and sufficient P_V, the P_V-np-Ni(Al)-40 electrode displays a low overpotential of 36 mV at a cathodic current density of 10 mA cm⁻² and an outstanding long-term operational stability for up to 94 h with a slight decay. Density functional theory (DFT) calculations confirm that P_V could induce the redistribution of electrons and significantly reduce the Gibbs free energy (ΔG_H*) of 2P_V-NiP₂ on the P site close to P_V (−0.055 eV). Moreover, the P_V is beneficial for enriching the electronic states nearby the Fermi level, thereby improving the conductivity of NiP₂ to achieve superior HER activity. This finding skillfully utilizes Al elements to not only create porous structures but also regulate the P_V concentration, opening up an accessible route to obtain P_Vvia dealloying-phosphorization, and boosting the development of high-performance HER electrocatalyst.