Low-Coke Plasma-Catalytic Methane Reforming in Pd- and TiO₂-Coated DBD Reactors

Catalyst degradation due to carbon coking remains a key barrier to the practical application of plasma-assisted reforming of methane (CH₄) and carbon dioxide (CO₂), despite renewed interest driven by global carbon-neutrality goals. In this study, we investigate reforming efficiency and coking resistance for three representative pathways; (i) dry reforming (CH₄ + CO₂), (ii) partial oxidation (CH₄ + O₂), and (iii) ozone-assisted reforming (CH₄ + O₃) using a dielectric barrier discharge (DBD) reactor whose electrodes are coated with either Pd or TiO₂. To identify optimum operating conditions that suppress carbon deposition while maintaining high reactivity, we varied the carbon-to-co-reactant ratio from 2:1 to 6:1, and product yields and carbon deposition were quantitatively analyzed via gas chromatography. Among all tested cases, ozone-assisted reforming in the TiO₂-coated DBD reactor achieved the highest methane conversion (21.5%), attributed to enhanced generation of reactive oxygen species and their surface reactions. These reactive species effectively oxidized solid carbon, thereby mitigating coking. These findings clarify plasma–catalyst interactions, point to plasma conditions that improve catalyst durability, and advance mechanistic understanding of plasma-assisted reforming systems.