Mechanism of Non-Equilibrium N₂/H₂ Plasma-Catalyzed Vacancy Generation and Surface Nitridation on WO₃ for Ammonia Synthesis

Surface nitridation and vacancy generation in non-equilibrium plasma are critical for catalytic electrochemical ammonia production. Recent studies have shown that using metal oxynitride catalysts can significantly improve Faradaic Efficiency (FE) of this process through surface nitridation. However, the mechanism for surface nitride formation in plasma is not fully understood.

This study aims to identify the mechanism of surface vacancy generation and surface nitridation in non-equilibrium N₂/H₂ dielectric barrier discharge plasma catalysis of a WO₃ catalyst. We hypothesize that active hydrogen containing species play a critical role in surface vacancy generation and subsequent nitridation. Through this work, we will report on the plasma properties, the active species production in plasma, and their impact on surface vacancy generation and nitridation. Preliminary results show that presence of ≥50% hydrogen in the feed gas composition significantly impacts the reduction of tungsten on the surface, which is an indirect indicator of oxygen vacancies. An understanding of these mechanisms can improve the FE of electrochemical ammonia synthesis.