Modeling of Transient Discharge Dynamics in an N2/H2 Planar Dielectric Barrier Discharge with Catalyst-Coated Barrier

Plasma-catalytic ammonia synthesis can operate without high temperatures and pressures, and its performance is closely tied to discharge modes. However, research on its microscopic discharge mechanisms remains limited. A 2D fluid model incorporating plasma-activated heterogeneous reactions was developed to investigate voltage polarity effects on discharge dynamics in an N2/H2 planar dielectric barrier discharge (DBD) reactor with catalyst-coated barriers. Under both polarities, discharge starts as a gas-phase streamer at the catalyst apex due to local field enhancement and then evolves into a surface ionization wave (SIW) with an order-of-magnitude higher electron density. Positive voltage restricts the SIW to the catalyst surface, whereas negative voltage induces SIWs on both the upper bare dielectric and the catalyst, driven by distinct charge accumulation patterns. During the short discharge pulse, the gas phase primarily functions as a radical generator, while surface reactions dominate NH3 synthesis. Because positive voltage effectively targets plasma energy to the catalyst surface, it yields a higher peak NH3 density near the catalyst (2.85 × 1019 m−3) compared to negative polarity (8.10 × 1018 m−3).