Porous reduced-graphene oxide supported hollow titania (rGO/TiO₂) as an effective catalyst for upgrading electromethanogenesis

Microbial electrochemical system (MES) for enhancing methane production has gained significant interest during the recent years, but the practical applications of MES are still far away due to several limitations such as low efficiency of cathodic electrochemical kinetics. In this study, novel porous reduced-graphene oxide/hollow titania (rGO/TiO₂) was successfully synthesized to be used as cathode catalyst for promoting electrochemical reduction of CO₂ to methane. The MES operation with rGO/TiO₂ catalyst exhibited 15.4% higher methane yield (0.383 ± 0.01 LCH₄/gCOD) and 13.4% higher production rate (152.38 mL/L.d) compared to control MES with bare carbon cloth cathode. The MES-rGO/TiO₂ produced around 33% higher in total Coulomb at 3837.9 ± 351.5C compared to the pristine cathode at 2887.92 ± 254.6C. Substrate degradation and volatile fatty acids conversion were significantly improved in the presence of rGO/TiO₂ catalyst. By using cyclic voltammetry and electrochemical impedance spectroscopy analysis, rGO/TiO₂ was proved to ease the electron transfer efficiency of working cathode for the conversion of electron to methane. The results suggest that porous rGO/TiO₂ can be a promising cathode catalyst to upgrade the performance of a scalable methane-producing MES-AD system.