Using a three-dimensional hydroxyapatite/graphene aerogel as a high-performance anode in microbial fuel cells

Bioaffinity of anode materials is a key factor for the power output of microbial fuel cells (MFCs). Anode surfaces with excellent biocompatibility can facilitate bacterial adhesion, biofilm propagation, and extracellular electron transfer. In this study, three-dimensional (3D) hydroxyapatite/graphene aerogel (HA/GA) was synthesized using a facile three-step method: hydrothermal treatment, dialysis, and freeze-drying. The HA/GA anode presented the excellent biocompatibility of HA and high conductivity of graphene. Moreover, the unique edge-to-edge crosslinked architecture of the HA/GA offered a large surface area for bacterial adhesion. Shewanella putrefaciens can generate more flavins through the introduction of highly biocompatible HA nanocrystals on the graphene sheets, leading to a rapid extracellular electron transfer between the biofilm and anode. An MFC containing a HA/GA anode delivered a maximum power density of 2.38 W m(-2), which was 1.83 times the power density achieved using a GA anode. Furthermore, MFCs equipped with HA/GA anodes were successfully utilized to drive a series of electrical appliances. The HA/GA anode possessed excellent biocompatibility, large surface area, superior hydrophilicity, and high conductivity, which were conducive for enhancing the surface bioaffinity and accelerating the interfacial charge transfer, thereby improving the electricity generation performance of the MFCs. This study has proven that HA is beneficial for enhancing the interface bioaffinity and that it can be applicable to MFC for high-performance bioelectricity harvesting.