Temperature-dependent structural and morphological engineering of nickel nitride via nitrogen plasma processing for...

Plasma-based surface modulation has gained attention in preparing electrode materials for high-performance electrocatalysis, but most methods involve multiple steps, typically a wet chemical synthesis followed by plasma treatment, limiting their further scalability. Solely plasma-driven surface structure control of electrocatalysts remains challenging due to the unclear dynamic factors during the plasma discharge, which extend beyond the known values of the initial set of plasma discharge parameters. Herein, we develop a cooling-mediated plasma strategy, enabling one-step modulation of the structure/phase of the metal electrocatalyst directly on its surface. With nickel as the substrate, a controlled surface thermal field during nitrogen plasma processing yields a distinct morphology and facet exposure of the resultant nitrides, attributed to the differential distribution of reactive N-species and varied surface dynamics of Ni, as verified by in situ plasma diagnostics and numerical simulations. Based on electrocatalytic performance testing and density functional theory (DFT) simulations, plasma-tailored nano-structures, under controlled surface temperature of the electrocatalyst through the use of a cooling component, deliver improved hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities. Our strategy offers a cost-effective approach for structural engineering in electrocatalysis.