Building electrode with three-dimensional macroporous interface from biocompatible polypyrrole and conductive graphene nanosheets to achieve highly efficient microbial electrocatalysis.

Bioelectrochemical systems (BESs) possess a great potential for simultaneous wastewater treatment and energy recovery. Rational construction of electrode materials could significantly improve the BESs performance. Three-dimensional macroporous electrode interface with high conductivity is highly desirable but challenging. In this work, we report a hierarchically nanostructured reduced graphene oxide nanosheets-polypyrrole (rGO@PPy) electrode via one-step electrodeposition technique. The prepared electrode was comprehensively studied by scanning/transmission electron microscopy, Raman spectroscopy, X-ray diffraction and electrochemical measurements, which showed that the rGO@PPy possessed a three-dimensional macroporous interconnecting scaffold with superior conductivity. The rGO@PPy electrode was utilized in Geobacter sulfurreducens inoculated BESs, and the maximum current density was 4.10 ± 0.02 mA cm-2, which is 8-fold higher than that of a rGO electrode (0.51 ± 0.03 mA cm-2), and is among the best performance reported for two-dimensional electrodes. The improved performance is ascribed to ultrahigh biomass concentration induced by "best match scale" between rGO@PPy and microbes, excellent extracellular electron transfer, as well as enhanced microbial affinity through the adequate exposure of biocompatible PPy layers. This work demonstrated a synergistic effect between rGO and PPy for the BESs performance improvement, and provided a new insight to design and fabricate a high-performance bioelectrode.