Simultaneous removal of Cr(VI) and phenol in a dual-chamber photocatalytic microbial fuel with NiCo2O4/MoS2/GF photocathode

Abstract

Efficient treatment and resource utilization of sewage are of great value for global sustainability. In this study, a composite photocathode was prepared by loading NiCo2O4 nanosheets and MoS2 nanoflowers to a graphite felt (GF)-based electrode through a two-step hydrothermal and calcination method. A photocatalytic microbial fuel cell (PMFC) was constructed using the NiCo2O4/MoS2/GF photocathode and carbon felt (CF) anode in a dual-chamber H-type battery. Cr(VI) and phenol were employed as target pollutants in the cathode chamber. The photoelectric performance of the NiCo2O4/MoS2/GF photocathode and the removal efficiency of the battery system were studied systematically. When a mixed solution of Cr(VI) and phenol was used, the removal rates of Cr(VI) and phenol after 24 h of light exposure were 8.13 % and 12.65 % higher than those when Cr(VI) or phenol was used alone, respectively. At the same time, the output power density of the battery in the mixed pollutants was 362.7 mW/m3, which was 45.78 % higher than that in the single Cr(VI) solution (248.8 mW/m3). The excellent performance of the PMFC was attributed to three reasons: (1) NiCo2O4 and MoS2 were simultaneously excited as two narrow-bandgap semiconductors, and the utilization rate of light energy was increased; (2) The Z-scheme heterojunction between NiCo2O4 and MoS2 improved the separation efficiency of the photoelectric carriers and retained the high valence band of NiCo2O4 and low conduction band of MoS2 to the greatest extent, which is crucial for the PMFC to achieve electronic export and double contaminant removal; and (3) the NiCo2O4 nanosheet and MoS2 nanoflower structures enhanced the contact between the catalysts and the pollutants.