More than the interface: Synergistic engineering of the interfacial and its subjacent layers followed by self-triggering for high efficient bioelectricity harvesting

Abstract

The practical application of microbial fuel cell (MFC) is severely impeded by its low output power density stemming from the low bacterial loadings and the sluggish extracellular electron transfer (EET) kinetics. Thus, the current collector designed to greatly enhance the electrocatalytic performance of microbial electrodes ought to possess both high hydrophilicity and high conductivity, which are, however, often mutually incompatible. Herein, to resolve this dilemma, a composite bioelectrode consisting of the poly(ionic liquid) functionalized single-walled carbon nanotube bundles (SWCNT-PIL) layer at the biotic-electrode interface and its subjacent hydrophilic graphene oxides (GO) layer is prepared. Bacterial adhesion is significantly enhanced, resulting from the positive charges of SWCNT-PIL and the hydrophilic GO. After self-reduction of GO by attached electricigens, the as-prepared mrGSP bioelectrode exhibits a maximum output power density of 4.808 W m−2, which is more than one order of magnitude larger than that of conventional carbon-based electrode (0.319 W m−2), because the SWCNT-PIL layer is capable of not only accelerating the flavin-based mediated electron transfer (MET), but also upregulating the membrane protein expression from 14.64% to 18.01% induced by the enhanced electric field, promoting the outer membrane c-type cytochromes-based direct electron transfer (DET). This work provides a new concept of synergistic engineering the interfacial and its subjacent layers to solve the dilemma between high hydrophilicity and high conductivity of the current collector surface for microbial electrocatalysis.