Facet Control of Nickel Nitride Nano‐Framework for Efficient Hydrogen Evolution Electrocatalysis via Auxiliary Cooling Assisted Plasma Engineering

Abstract The precise facet modulation of transition metal nitrides (TMNs) has been regarded as an essential issue in boosting electrocatalytic H 2 production. Compared to thermal nitridation, the plasma technique serves as a favorable alternative to directly achieve TMNs, but the apparent surface heating effect during plasma treatment inevitably causes the thermally stabilized nitride formation, resulting in the deterioration of the highly reactive facet. To optimize the hydrogen evolution reaction (HER) behavior, an auxiliary cooling assisted plasma system to selectively expose Ni 3 N (2‐10) with favorable activity by controlling surface heating during plasma nitridation is designed. The resultant nickel nitride (cp‐Ni 3 N) nano‐framework delivers exceptional catalytic performance, evidenced by its low overpotential of 58 and 188 mV at the current density of 10 and 100 mA cm −2 for HER, in stark comparison with that of normal plasma and thermally fabricated Ni 3 N. Operando plasma diagnostics along with numerical simulation further confirm the effect of surface heating on typical plasma parameters as well as the Ni 3 N nanostructure, indicating the key factor responsible for the high‐performance nitride electrocatalyst.