Self-assembled hierarchical porous carbon nanotube sponge bioanode for energy harvesting and gaseous toluene removal

Microbial fuel cells (MFCs) have emerged as a promising technology with potential for volatile organic compounds (VOCs) treatment and energy recovery. However, the low efficiency of electron transfer between microorganisms and electrodes has limited their degradation ability and power output. To address this issue, we designed a macroscopic hierarchical porous super-aligned carbon nanotube (SACNT) sponge bioanode. The hierarchical structure of the SACNT anode exhibited an appropriate distribution of macro/mesopores. The large pores facilitated biofilm formation and mass transfer, enhancing direct electron transfer between bacteria and SACNTs. The abundant mesopores augmented adsorption and electrochemical reaction sites, thereby enhancing flavin-mediated indirect electron transfer. This hierarchical pore structure induced the formation of biofilms mainly composed of electroactive bacteria and toluene-degrading bacteria, promoting toluene removal and power generation. The MFC demonstrated an exceptional power density of 726.18 mW m ? 2, surpassing existing toluene-fueled MFCs, while achieving the toluene elimination capacity of 61.29 g m ? 3 h-1.