A feasible strategy for microbial electrocatalytic CO2 reduction via whole-cell-packed and exogenous-mediator-free rGO/Shewanella biohydrogel

Bioelectrochemical CO2 reduction (bio-CO2R) provides a sustainable and carbon neutral power-to-chemical route. Whole-cell electrosynthesis is one of the attractive strategies to realize CO2R due to its simple and low-cost superiorities. However, it is still challenging to overcome the sluggish transmembrane electron transfer of microorganisms without exogenously added mediators. Here, we described the fabrication of biohydrogel that contains bio-reduced graphene oxide (rGO) and living electroactive bacteria (EAB) for bio-CO2R. The EAB exhibited surprising ability to self-assemble biohydrogel that was further served as biocathode to drive CO2-to-formate electrosynthesis. With the close interaction between EAB and rGO nanosheets, the transmembrane electron transfer achieved at high Faradaic efficiency (similar to 99.5 %) and 46-fold increase of formate titer without exogenous mediator. This work provided the facile and practical approach to bridge the bacterial cell and electrode for efficient electron transfer and implied the new possibility to store the electric energy into chemicals with bio-CO2R.