Plasma-Catalytic Ammonia Synthesis beyond the Equilibrium Limit

We explore the consequences of nonthermal plasma-activation on product yields in catalytic ammonia synthesis, a reaction that is equilibrium-limited at elevated temperatures. We employ a minimal microkinetic model that incorporates the influence of plasma-activation on N-2 dissociation rates to predict NH3 yields into and across the equilibrium-limited regime. NH3 yields are predicted to exceed bulk thermodynamic equilibrium limits on materials that are thermal-rate-limited by N-2 dissociation. In all cases, yields revert to bulk equilibrium at temperatures at which thermal reaction rates exceed plasma-activated ones. Beyond-equilibrium NH3 yields are observed in a packed bed dielectric barrier discharge reactor and exhibit sensitivity to catalytic material choice in a way consistent with model predictions. The approach and results highlight the opportunity to exploit synergies between nonthermal plasmas and catalysts to affect transformations at conditions inaccessible through thermal routes.