Biomimetic anode with atomically dispersed iron sites to enhance biotic-abiotic interfacial interaction towards efficient wastewater energy recovery in bioelectrochemical systems

Bioelectrochemical systems (BESs) are promising for future wastewater treatment towards carbon neutrality. Hemes, as the active centers of outer-membrane c-type cytochromes, play an important role in anodic electron transfer. In this work, a biomimetic Fe-Nx incorporated carbon membrane (Fe-NCM) mimicking the heme active center was proposed based on a nanocage confinement-electrospinning strategy and applied as the anode in BESs. The aligned carbon fibers with high electrical conductivity could serve as the electron "expressway" for swift electron transfer while the Fe-Nx nexus served as the "gas station" and endowed the membrane anode with boosted redox activity. The Fe-NCM anode featuring great biocompatibility and electrochemical activity was conducive to microbe adhesion and biotic-abiotic interfacial interaction. The power output and chemical oxygen demand (COD) removal rate constant in the BES with this Fe-NCM anode reached 1406 +/- 44 mW m- 2 and 0.42 +/- 0.01 h-1 under filtration operation mode, which were 156% and 191% as high as those of the pristine carbon membrane. The introduction of Fe-Nx species exerted a significant influence on the anodic biofilm property, composition and function, which were of importance to bolstering wastewater energy conversion. Metagenomics unveiled that simultaneous intensification of intracellular electron production and extracellular electron transfer processes was achieved in the Fe-NCM BES. The Fe-NCM anode with electroactive Fe-Nx sites facilitated the biotic-abiotic interfacial interaction in BESs and highlighted the rational design of anodes for efficient waste-water treatment and energy conversion.