Theoretical insight into the essential role of charged surface for ammonia synthesis: Si-decorated carbon nitride electrode

Abstract

We report a new Si-decorated carbon nitride (C₅N₂H₂) electrode for the sustainable generation of a hydrogen storage medium, ammonia (NH₃), which not only possesses sound electrical conductivity, dynamic stability, and electrochemical activity for the nitric oxide/nitrogen reduction reaction (NORR/NRR), but also provides an option for designing metal-free electrodes. Most importantly, it is found that the charged surface is of great significance to the improved catalytic performance compared to the neutral condition, but this has always been overlooked. Herein, by means of DFT computations, the stubborn chemical bonds of NO and N₂ can be entirely activated under an electron density of −2.15 × 10⁻² e Å⁻² on the Si-C₅N₂H₂ material with an inconsiderable kinetic energy barrier (0.28 eV) along the protonation path. In brief, this finding paves a way for understanding false results by theoretical calculations compared to experiments.