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/TiO 2) was successfully synthesized to be used as cathode catalyst for promoting electrochemical reduction of CO 2 to methane. The MES operation with rGO/TiO 2 catalyst exhibited 15.4% higher methane yield (0.383 ± 0.01 LCH 4 /gCOD) and 13.4% higher production rate (152.38 mL/L.d) compared to control MES with bare carbon cloth cathode. The MES-rGO/TiO 2 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/TiO 2 catalyst. By using cyclic voltammetry and electrochemical impedance spectroscopy analysis, rGO/TiO 2 was proved to ease the electron transfer efficiency of working cathode for the conversion of electron to methane. The results suggest that porous rGO/TiO 2 can be a promising cathode catalyst to upgrade the performance of a scalable methane-producing MES-AD system. • Porous rGO and hollow TiO 2 was successfully synthesized and applied as catalyst of MES cathode. • Catalyzed MES enhanced 20% and 33% methane accumulation and coulomb generation, respectively. • rGO/TiO 2 eased the decomposition of substrate and VFAs for a better methane production rate. • rGO/TiO 2 enhanced catalytic activity and lowered charge transfer resistance of working cathode. [ABSTRACT FROM AUTHOR]