Effect of crystallization degree on H2O splitting performance in Nickel–Based composite electrocatalysts

Efficient splitting of H 2 O necessitates the utilization of highly active and stable electrocatalysts. In this study, a nickel−based composite electrocatalyst, specifically a graphene−loaded nickel butanedione oxime composite denoted as Ni(DMG) 2 @G, was successfully synthesized via a mechanochemical strategy, and aimed to investigate its performance in H 2 O splitting. When operated in an alkaline medium (1 M KOH), the low−crystallinity Ni(DMG) 2 @G catalyst exhibited novel electrocatalytic properties for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) during H 2 O splitting. Notably, the overpotentials for HER and OER were merely 76 mV and 234 mV, respectively, at a current density of 10 mA cm −2 . Most significantly, the catalyst also demonstrated commendable catalytic performance in the overall H 2 O splitting process, rendering Ni(DMG) 2 @G an effective bifunctional catalyst. The exceptional catalytic performance of Ni(DMG) 2 @G can be primarily attributed to two factors. Firstly, the mechanochemical synthesis strategy resulted in the formation of low−crystallinity and small−sized Ni(DMG) 2 particles, which exposed a substantial number of active sites while simultaneously increasing the specific surface area. Secondly, theoretical calculations indicated that the combination of Ni(DMG) 2 and graphene significantly enhanced the electrical conductivity and accelerated the electron transfer process. This study offers a novel synthesis strategy for the preparation of high−quality electrocatalysts and contributes to the advancement of H 2 O electrolysis technology.