Interface engineering on super-hydrophilic amorphous/crystalline NiFe-based hydroxide/selenide heterostructure nanoflowers for accelerated industrial overall water splitting at high current density.

Designing heterojunction catalysts with energy effects at the interface, particularly combining the surface structure advantages of super-hydrophilic interfaces with the high activity advantages of bimetal synergistic optimisation, is the key to developing economical and efficient industrial electrocatalytic water-splitting catalysts. In this study, a coupled nanoflower-like NiFe(OH)x/(Ni, Fe)Se heterostructure catalyst supported on Ni foam (NF) (NFSe@NFOH/NF) was designed and successfully prepared using hydrothermal and electrodeposition strategies. Owing to the electron interaction at the heterogeneous amorphous (NFOH)/crystalline (NFSe) interface and the bimetallic synergistic effect of Ni and Fe, the prepared NFSe@NFOH/NF exhibited excellent and stable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) catalytic properties, with low overpotentials of 214/276 mV at 100 mA⋅cm-2 and 262/340 mV at 500 mA⋅cm-2. The assembled water electrolyser comprising NFSe@NFOH/NF || NFSe@NFOH/NF needed only small voltages of 1.73 and 1.85 V to yield current densities of 100 and 500 mA⋅cm-2, respectively. This study offers an innovative design idea for the rational adoption of interface engineering and amorphous-crystalline engineering techniques to construct catalysts with excellent catalytic activity and stability for electrocatalytic overall water splitting (EOWS) at a high current density, which further facilitates the advancement of sustainable energy technology in the future.