Hydrophilicity Controllable rGO Sponge for Living Bioelectrogenesis Electrode*

Herein, we report on a novel bioelectrode material that consists of partially reduced graphene oxide (rGO) sponge and Shewanella Onedensis MR-1 bacteria. We develop a new facile approach for the enhancement of output current of the sponge-bacteria electrode by optimization of the surface chemistry of sponge-electrode surface. We achieve simultaneous tuning hydrophilicity and conductivity of rGO by adjusting the reduction temperature of graphene oxide (GO). Thermal reduction is a sustainable approach that allows us to produce the scaffolds for bacteria growth with excellent biocompatibility without usage of chemicals. We find the rGO-sponge-electrode exhibit a GO-reduction-temperature reliable bio-current generation performance due to the discrepancy in rGO’s hydrophilicity and conductivity, where the sponge-bacteria shows a superior performance with the bio-current density reached 135 mA·m^-2 in chronoamperometry test at the reduction temperature of 375°C. Furthermore, in contrast to existing polymer-based microbial electrode requiring several days activation time to form a conductive network, our rGO-sponge-electrode doesn’t require the activation time. The proposed here novel biocompatible graphene-based electrodes can be used for the design of the next generation of renewable energy-powered devices.