Multilayered structure and activity of electroactive biofilms in response to the switch from microbial fuel cell to microbial electrolysis cell

Bioelectrochemical systems (BESs) operated under microbial fuel cell (MFC) mode and microbial electrolysis cell (MEC) mode occupy different elimination capacities of organic pollutants. To explore the underlying mechanism, an electroactive biofilm is established rapidly in a sponge-like polyaniline @ carbon nanotube (PANI@CNT) electrode for gaseous toluene removal, and the response of the multilayered structure and activity of it to the mode switch from MFC to MEC is investigated in this work. Affected by the switch, the height, area proportion of microbial cells, and amount of living cells of the biofilm increase by 1.22-, 2.52-, and 2.68-fold, respectively. The PANI@CNT-MEC exhibits a highest elimination capacity of 216.7 g m- 3 h-1, which is much greater than the literature values. Moreover, it is revealed that the enhanced toluene adsorption of PANI@CNT, the low-resistance mass transport into the biofilm, and the enriched functional microorganisms all contribute to the homogeneous biofilm activity and the superior toluene degradation ability. These findings could provide valuable insights into the design and operation of BESs for efficient pollutant removal.