In this research, conversion of carbon dioxide in the presence of TiO2 supported NiO catalyst has been investigated in a pulsed surface-wave sustained microwave discharge. The catalyst is prepared by combination of impregnation and plasma-treatment methods. The decomposition of TiO2 supported nickel nitrate was done by plasma, induced in three different gases (O-2, Ar, CO2). NiO/TiO2 catalysts were formed. The supplied gas has a prominent effect on the chemical and physical properties of the prepared catalysts. The catalyst prepared with an Ar plasma increases almost by a factor of 2 the CO2 conversion and energy efficiencies, while the O-2 or CO2 plasma prepared catalysts show little effect on the CO2 conversion in comparison with catalyst-free plasma assisted dissociation. The results from the catalyst characterization by different techniques demonstrated that Ar plasma pre-treatment resulted in formation of oxygen vacancies. Dissociative electron attachment of CO2 at the catalyst surface enhanced by oxygen vacancies and plasma electrons could explain the improved conversion and energy efficiency. A constant catalytic activity was observed indicating continuous catalyst regeneration under reactor conditions. A mechanism of plasma-catalysis synergy is proposed. (C) 2016 Elsevier B.V. All rights reserved.