Exploring the potential of metal oxides as cathodic catalysts in a double chambered microbial fuel cell for phenol removal and power generation

Detection of high phenol concentrations in industrial wastewater contributed to the need for more efficient wastewater treatment approaches. This study compared and investigated the different metal oxides as cathodic catalysts in a double chambered microbial fuel cell (MFC) for simultaneous phenol removal and bioelectricity generation. Metal oxides such as copper (II) oxide (CuO), manganese dioxide (MnO2) and tin (IV) oxide (SnO2) were synthesized and loaded on a carbon (C) plate, respectively, for application as cathode in the MFC. Results revealed that total chemical oxygen demand and phenol removal efficiency of MFC depleted in the order of CuO/ C (96.69 and 100 %) > beta-MnO2/C (90.93 and 94.41 %) > alpha-MnO2/C (84.69 and 90.17 %) > SnO2/C (80.25 and 84.84 %) > bare C (70.48 and 77.06 %) cathode due to the deterioration in the oxygen reduction reaction reactivity. Besides, the solution pH was crucial in determining the catalyst's surface charge properties. At pH 8, higher solution conductivity and stronger electrostatic attraction between positively charged CuO and anionic phenol molecules were favourable for the complete phenol removal. This phenomenon contributed to a 1.77-fold higher maximum power density attained at pH 8 (29.24 mW m-2) than that of pH 11 (16.52 mW m-2) due to more electrons could be utilized for electricity generation. This study provided valuable information on the facile fabrication of cost-effective cathodic catalysts in a double chambered MFC for wastewater treatment and bioelectricity generation.