Plasma-Assisted Surface Nitridation of Proton Intercalatable WO₃ for Efficient Electrocatalytic Ammonia Synthesis

Electrocatalytic nitrogen reduction (eNRR) offers a green pathway for the production of NH₃ from N₂ and H₂O under ambient conditions. Transition metal oxynitrides (TMO _<i>x</i> N _<i>y</i> ) are among the most promising catalysts but face challenges in achieving a high yield and faradaic efficiency (FE). This work develops a hybrid WO _<i>x</i> N _<i>y</i> /WO₃ catalyst with a unique heterogeneous interfacial complexion (HIC) structure. This design enables <i>in situ</i> generation and delivery of highly active hydrogen atoms (H*) in acidic electrolytes, promoting nitrogen hydrogenation and the formation of nitrogen vacancies (Nv) on the WO _<i>x</i> N _<i>y</i> surface. This significantly enhances the selectivity of eNRR for NH₃ synthesis while suppressing the hydrogen evolution reaction (HER). A simple two-step fabrication processmicrowave hydrothermal growth followed by plasma-assisted surface nitridationwas developed to fabricate the designed catalyst electrode, achieving an NH₃ yield of 3.2 × 10^-10 mol·cm^-2·s^-1 with 40.1% FE, outperforming most TMN/TMO _<i>x</i> N _<i>y</i> electrocatalysts. Multiple control experiments confirm that the eNRR follows an HIC-enhanced Mars-van Krevelen (MvK) mechanism.