Plasma Chemistry in an Atmospheric Pressure Ar/NH3 Dielectric Barrier Discharge

An atmospheric pressure dielectric barrier discharge (DBD) in Ar/NH3 (0.1–10%) mixtures with a parallel plate electrode geometry was studied. The plasma was investigated by emission and absorption spectroscopy in the UV spectral range. Discharge current and voltage were measured as well. UV absorption spectroscopy was also employed for the detection of stable products in the exhaust gas. To clarify the different processes for ammonia decomposition, N2 (2–10%) was added to the plasma. Modeling of the chemical kinetics in an Ar/NH3 plasma was performed as well. The dominant stable products of an atmospheric pressure Ar/NH3 DBD are H2, N2 and N2H4. The hydrazine (N2H4) concentration in the plasma and in the exhaust gases at various ammonia concentrations and different discharge powers was measured. Thermal N2H4 decomposition into NH2 radicals may be used for NOx reduction processes. The differences in the optical emission spectra of NH radicals formed in Ar/NH3 plasma with various ammonia concentrations (0.7, 2, and 10%) were associated with different excitation mechanisms of NH radicals.