Climate change and global warming caused by the increasing emissions of greenhouse gases (such as CO 2) recently attract attention of the scientific community. The combination of plasma and catalysis is of great interest for turning plasma chemistry in applications related to pollution and energy issues. In this chapter, our recent research efforts related to optimization of the conversion of CO 2 and CO 2 /H 2 O mixtures in a pulsed surface-wave sustained microwave discharge are presented. The effects of different plasma operating conditions and catalyst preparation methods on the CO 2 conversion and its energy efficiency are discussed. It is demonstrated that, compared to the plasma-only case, the CO 2 conversion and energy efficiency can be enhanced by a factor of ∼2.1 by selecting the appropriate conditions. The catalyst characterization shows that Ar plasma treatment results in a higher density of oxygen vacancies and a comparatively uniform distribution of NiO on the TiO 2 surface, which strongly influence CO 2 conversion and energy efficiencies of this process. The dissociative electron attachment of CO 2 at the catalyst surface enhanced by the oxygen vacancies and plasma electrons may explain the increase of conversion and energy efficiencies in this case. A mechanism of plasma-catalytic conversion of CO 2 at the catalyst surface in CO 2 and CO 2 /H 2 O mixtures is proposed.