BACKGROUND Plasma catalysis has emerged as a powerful tool in converting a gas or gas mixture into other value-added or environment-friendly chemicals. However, a substantial research effort is needed to further understand the physical and chemical interactions between plasma and catalysts, and their contribution to the chemical reactions. RESULTS For a given energy density (ED) of 535 +/- 25 J L-1, a dielectric barrier discharge (DBD) reactor packed with Al2O3 achieved higher NO2 selectivity and N2O concentration than the DBD reactor alone. Two kinds of supported catalysts (MnOx/Al2O3 and CoOx/Al2O3) with different loading amounts were prepared to investigate the NO oxidation performance of the plasma-catalytic process. The results indicated that 5 wt% MnOx/Al2O3 presented higher NO2 selectivity and N2O concentration than other catalysts. Packing the DBD reactor with catalysts also changed its discharge behavior. The discharge behavior of the packed-bed DBD reactor also changed with variation in the loading amount of active metal oxide from 0 to 15 wt%, resulting in changes in NO oxidation performance. Fourier transform infrared (FTIR) and temperature-programmed desorption (TPD) analysis results indicated that nitrates were formed during the non-thermal plasma (NTP)-assisted catalytic process. CONCLUSION Packing catalysts into the NTP area can not only change the discharge behavior but also improve the oxidation performance of NTP. Both NO oxidation performance and N2O formation for the NTP-assisted catalytic process have presented significant enhancement. Reducing N2O formation will still be a big challenge for NTP systems used in environmental applications. (c) 2019 Society of Chemical Industry