Low-Temperature Plasma-Assisted Catalytic Dry Reforming of Methane over CeO₂ Nanorod-Supported NiO Catalysts in a Dielectric Barrier Discharge Reactor

Nonthermal plasma (NTP)-assisted catalytic dry reforming of methane (DRM) is considered a powerful single-stage reaction mechanism because of its ability to activate normally stable CO 2 and CH 4 at a low temperature under ambient conditions. The thermodynamic barrier of DRM requires a high operating temperature (>700 °C), which can be reduced by nonequilibrium plasma. Herein, we present a method for the wet-impregnation synthesis of CeO 2 nanorod (NR)-supported 5 and 15 wt % NiO catalysts for efficient NTP-promoted DRM with an applied power in the range of 24.9–25.8 W (frequency: 20 kHz), a CH 4:CO 2 feed gas ratio of 100:250 sccm, and a total flow rate of 350 sccm. The presence of NTP dramatically increased the reaction activity, even at 150 °C, which is usually inaccessible for thermally catalyzed DRM. The CH 4 and CO 2 conversion reaches a maximum of 66 and 48%, respectively, at 500 °C with the 15 wt % NiO/CeO 2 NR catalyst, which are much higher than the values obtained for the 5 wt % NiO/CeO 2 NR catalyst under the same conditions. According to the X-ray photoelectron spectroscopy profile for 15 wt % NiO/CeO 2 NR, a higher concentration of NiO on CeO 2 increases the proportion of Ce 3+ in the catalyst, suggesting enhanced oxygen vacancy concentration with an increased amount of NiO loading. Additionally, a higher NiO loading promotes a higher rate of replacement of Ce 4+ with Ni 2+, which generates more oxygen vacancies due to the induced charge imbalance and lattice distortion within the CeO 2 lattice. As a result, it can be inferred that the incorporation of Ni ions into the CeO 2 structure resulted in inhibited growth of CeO 2 crystals due to the creation of a Ni x Ce 1– x O 2−α solid solution and the production of oxygen vacancies.