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Nitrogen doped carbon nanoparticles (NDCN) were applied to modify the carbon cloth anodes of microbial fuel cells (MFCs) inoculated with Shewanella oneidensis MR-1, one of the most well-studied exoelectrogens. Experimental results demonstrated that the use of NDCN increased anodic absorption of flavins ( i.e. , the soluble electron mediator secreted by S. oneidensis MR-1), facilitating shuttle-mediated extracellular electron transfer. In addition, we also found that NDCN enabled enhanced contact-based direct electron transfer via outer-membrane c-type cytochromes. Taken together, the performance of MFCs with the NDCN-modified anode was enormously enhanced, delivering a maximum power density 3.5 times’ higher than that of the MFCs without the modification of carbon cloth anodes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Shewanella loihica PV-4 exhibited high performance in reducing CO 2 to formate. • A novel three-dimensional biological self-assembled cathode was constructed. • No involvement of electron mediators was found in whole cell catalysis. • Faraday efficiency of bioelectrosynthetic CO 2 -to-formate reached 99.95%. Bioelectrochemical CO 2 reduction (bio-CO 2 R) provides a sustainable and carbon neutral power-to-chemical route. Whole-cell electrosynthesis is one of the attractive strategies to realize CO 2 R 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-CO 2 R. The EAB exhibited surprising ability to self-assemble biohydrogel that was further served as biocathode to drive CO 2 -to-formate electrosynthesis. With the close interaction between EAB and rGO nanosheets, the transmembrane electron transfer achieved at high Faradaic efficiency (∼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-CO 2 R. [ABSTRACT FROM AUTHOR]