Bioelectronic and photogenerated electron synergistic catalyzed removal of chlorhexidine: Degradation and mechanism.

The extensive use of the antimicrobial compound chlorhexidine (CHD) has emerged as a significant threat to both the ecological environment and human health. To address this concern, a photo-electrochemical cell-microbial fuel cell (PMFC) system was studied for CHD removal by incorporating, for the first time, the photocatalysts black phosphorus/carbon nitride (BPCN) and Cu2O into the bioanode and air cathode of an MFC, respectively. By combining electrochemical, macro-genomic, and intermediate product analyses, the underlying mechanisms of bioelectronic and photoelectronic synergies were elucidated. Specifically, the bioanode and the energy band difference between BPCN and Cu2O accelerated the bioelectronic and photoelectronic transfer, reduced the reaction barrier, and enhanced the cathodic dechlorination pathway. Consequently, the PMFC showed a 31.4-fold and 8.0-fold increase in CHD removal rate compared to the MFC and PEC, respectively. The photogenerated electrons, on the other hand, acted as key cofactors, replacing cytochrome c and facilitating electron transfer at the microbial-electrode interface, which improved the system's energy yield by 53.9 %. Additionally, illumination selectively enhanced the abundance of anode functional species, carbon metabolism, and interspecific cooperation, resulting in a 4.03-fold increase in the removal of CHD and its intermediates. These findings offer new perspectives on biochemically sustainable environmental remediation for recalcitrant pollutants.