Experimental and kinetic study of non-equilibrium plasma driven NH₃ decomposition

This study establishes the first low temperature kinetic model for plasma-assisted ammonia decomposition based on the experiment in a dielectric barrier discharge reactor, addressing the limitations in both conventional combustion chemical kinetics models and plasma models and improves the model prediction at low temperatures. By integrating the diagnostics with kinetic modeling, a multi-scale framework is developed which explicitly couples electron-impact reactions with excited Ar* pathways. The model uniquely achieves 53.4 % higher predictive accuracy than combustion models through systematic validation against measured concentrations. Key mechanistic insights reveal: (i) Plasma-driven processes predominantly govern the initial decomposition of NH₃ and subsequent H₂ formation, with direct electron-impact dissociation of NH₃ accounting for over 95 % of the total H₂ yield; (ii) Ar* serves dual roles as energy carrier (11.55 eV excitation) and reactive collision partner, enabling efficient energy transfer via quenching-induced NH₃ decomposition (Ar*+H + NH₃ → NH₂ + 2H + Ar); (iii) N₂ formation proceeds through NH₂ dimerization (NH₂ + NH₂=N₂H₄) followed by sequential H-abstraction dehydrogenation (N₂H₄ → N₂H₃ → N₂H₂ → NNH → N₂). These findings provide fundamental guidelines for designing plasma-assisted NH₃ decomposition, demonstrating the viability of low-temperature on-demand hydrogen production with enhanced energy efficiency.