Synergistically promoting microbial biofilm growth and interfacial bioelectrocatalysis by molybdenum carbide nanoparticles functionalized graphene anode for bioelectricity production

An electrode for microbial electrocatalysis needs to interface biological-catalytic process with electrochemical-catalytic reaction, thereby both high loading of microbes (biocatalysts) and robust interfacial-catalytic activity are essential. Inspired by this insight, molybdenum carbide hybridized graphene nanocomposite is developed as an anode material for microbial fuel cell through a facile layer-by-layer electrostatic assembly followed by high-temperature carburization approach. Small-sized molybdenum carbide nanoparticles with good crystallinity are uniformly anchored on hierarchically porous-structured graphene, which greatly promotes the adhesion of Shewanella putrefaciens (an electricigen) cells to form compact electroactive biofilm with benefits from excellent biocompatibility and chemical flexibility of nanostructured molybdenum carbide. In return, the well-grown biofilm in-situ generates abundant electroactive biomolecules like flavins (endogenous electron shuttles) around the electrode interface, which can be used directly by molybdenum carbide nanocatalysts with outstanding electrocatalytic activity, thus leading to a dramatically enhanced extracellular electron transfer from bacterial cells to electrode. The developed hybrid anode delivers a maximum power density of 1697 mW m^-2 with reliable stability, more than 2-fold and 13-fold over the undecorated graphene and carbon cloth, respectively. This work illustrates an efficient route to tailor microbial electrode with highly active nanocatalysts for synergistically boosting bioelectrocatalytic kinetics through integrating biological catalysis with electrochemical one.