Radio frequency plasma-engraved vacancy engineering towards robust hydrogen-evolving catalysts with large-current stable catalytic activity for over 1000 h

Abstract

The proper incorporation of defects in existing materials, including cationic and anionic vacancies, would act as suitable promoters for enhancing the energy efficiency of water electrolysis at large current densities, but controllably creating effective vacancies in electrocatalysts remains a formidable challenge. Here we report that a sandwich-like nanoporous hybrid catalyst consisting of double-layer nickel nitride (Ni₃N) intercalated by a metallic Ni layer is creatively synthesized through room-temperature ionized nitrogen radio frequency plasma bombardment with short reaction times. This unique strategy not only ensures good electron transfer between Ni and Ni₃N, but also provides abundant nitrogen vacancies as the active species ameliorating initial water dissociation and subsequent hydrogen adsorption as evidenced by the density functional theory (DFT) calculations, thus greatly enhancing the hydrogen evolution kinetics. Owing to the introduction of nitrogen vacancies and the synergistic interaction between Ni₃N and Ni species, the resultant catalyst exhibits excellent hydrogen-evolving activity approaching the state-of-the-art Pt catalysts, featured by considerably low overpotentials of 14 and 180 mV to achieve 10 and 500 mA cm⁻², superior to most available non-precious electrocatalysts, thus considerably facilitating the electrochemical hydrogen production at low voltages under large current density. Remarkably, this catalyst exhibits outstanding durability at large current densities (200–500 mA cm⁻²) for over 1000 h, which is in sharp contrast to most of the non-noble electrocatalysts with tens of hours of stability. This simple strategy does not involve any cumbersome synthetic procedures, paving a new avenue toward the rapid synthesis of robust hydrogen-evolving electrocatalysts for alkaline water electrolysis.