Protonation-Gated Hydrogen Evolution Enabled by Pyridinic Nitrogen on Graphene Edges

As a cost-effective and acid-stable alternative to noble-metal catalysts, the rational design of high-performance metal-free electrocatalysts hinges on in-depth mechanistic insights and precise structural regulation. Graphene and its derivatives hold great promise, yet their heteroatom doping often compromises lattice integrity and intrinsic electronic properties. Herein, we report highly active HER electrocatalysts with ceramic-protected graphene edges that enable N₂ plasma functionalization while largely preserving the graphitic framework. Using in situ electrochemical characterization, we systematically investigate the catalytic role of nitrogen species in a ceramic-protected graphene edge architecture. The optimized catalyst delivers an overpotential of 46 mV at 10 mA cm^-2, 6-fold lower than that of pristine edges even after 2000 CV cycles, outperforming most reported metal-free catalysts and approaching state-of-the-art metal-based benchmarks. Most importantly, these results propose a plausible protonation-gated mechanism: under acidic HER conditions, reversible protonation/deprotonation near-edge pyridinic N may tune α-C sites for favorable H adsorption, enhancing HER activity.