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

Efficient splitting of H2O 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 H2O 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 H2O 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 H2O 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 H2O electrolysis technology.