The accelerating carbon dioxide fixation of R. palustris under dark condition by iron nitride nanoarrays increasing electroactive bacteria outward extracellular electrons transfer in bioelectrochemical system

An EET-CO2-fixation system was constructed, where carbon cloth with Fe2N nanoarrays grown in situ on its surface (Fe2N-CC) was employed as the anode for enriching electrochemically active bacteria (EAB, 96.327 %) and enhancing outward extracellular electron transfer (EET), while R. palustris adhered to the cathode for CO2 fixation. The electrons transferred by EET on the Fe2N-CC anode under dark conditions were found to provide more ATP and reducing power to the R. palustris for cathodic CO2 fixation in the system, in which the proliferation level of R. palustris was comparable to the photoautotrophy. Furthermore, experiments and DFT calculations confirmed that Fe2N nanoarrays can accelerate the direct electron transfer with more proteins in extracellular polymorphic substances, nanowires, c-type cytochromes, and Fe3+/Fe2+, as well as facilitate indirect electron transfer by secreting riboflavin and naphthoquinone. This system can provide new ideas for photosynthetic bacteria to achieve all-weather biological carbon sequestration.