Tailoring hierarchically porous graphene architecture by carbon nanotube to accelerate extracellular electron transfer of anodic biofilm in microbial fuel cells

To overcoming their respective shortcomings of graphene and carbon nanotube, a hierarchically porous multi-walled carbon nanotube@reduced graphene oxide (MWCNT@rGO) hybrid is fabricated through a versatile and scalable solvent method, in which the architecture is tailored by inserting MWCNTs as scaffolds into the rGO skeleton. An appropriate amount of inserted 1-D MWCNTs not only effectively prevent the aggregation of rGO sheets but also act as bridges to increase multidirectional connections betweeb 2-D rGO sheets, resulting in a 3-D hierarchically porous structure with large surface area and excellent biocompatibility for rich bacterial biofilm and high electron transfer rate. The MWCNT@rGO(1:2)/biofilm anode delivers a maximum power density of 789 mW m(-2) in Shewanella putrefaciens CN32 microbial fuel cells, which is much higher than that of individual MWCNT and rGO, in particular, 6-folder higher than that of conventional carbon cloth. The great enhancement is ascribed to a synergistic effect of the integrated biofilm and hierarchically' porous structure of MWCNT@rGO(1:2)/biofilm anode, in which the biofilm provides a large amount of bacterial cells to.raise the concentration of local electron shuttles for accelerating the direct electrochemistry on the 3-D hierarchically porous structured anodes. (C) 2016 Elsevier B.V. All rights reserved.