Electron-rich graphene layer induces a H-down configuration of water molecules for efficient ammonia electrosynthesis...

Electron-rich catalytic surfaces have been widely employed in the electrochemical reduction of nitric oxide (eNORR) for ammonia electrosynthesis. However, their influence on the reaction mechanism, particularly solvent effects, remains poorly understood. In this study, we developed an electron-rich core/shell catalyst by encapsulating tungsten trioxide with a graphene layer (WO_3-x@GR) to investigate its role in modulating solvent effects. This catalyst achieved an ammonia yield of 4365 μmol mg^-1 h^-1 and a faradaic efficiency (FE) of 91.1% at -0.54 V vs. RHE over 100 h of continuous operation, surpassing most recently reported catalysts. Electronic structure analyses demonstrated that oxygen vacancies (Ov) in the WO₃ core facilitated interfacial electron transfer, thereby generating electron-rich active sites within the graphene (GR) shell. Moreover, ab initio molecular dynamics (AIMD) simulations indicated that water molecules preferentially adopted an H-down orientation at these active sites, weakening nitric oxide (NO) adsorption through hydrogen bonding while enhancing NOH adsorption via hydrogen-atom repulsion. This reorientation lowered the energy barrier of the potential rate-determining step (*NO → *NOH) from 2.18 eV to 1.16 eV, thereby significantly enhancing eNORR activity. Collectively, this study provides new molecular-level insights into solvent effects in eNORR and offers guidance for the rational design of high-performance electrocatalysts.