Highly Boosted Microbial Extracellular Electron Transfer by Semiconductor Nanowire Array with Suitable Energy Level

Microbial extracellular electron transfer (EET) with high performance and good controllability is always desired in various bioelectric applications. Depending on the redox state, C-type cytochromes located across the outer membranes (OMCs) mediate EET with different behaviors. Here, by incorporating Sn-doped In₂O₃ nanowire array with flat F-doped In₂O₃ (FTO), a composite electrode is developed that can highly boost EET by over 60 times at a certain potential of 0.2 V, where normally only limited EET current is observed on a conductive electrode. It is proposed that the underlay FTO with bias 0.2 V promotes EET via OMCs by physical contacting with microbes, while the semiconductor nanowires provide a suitable energy level to facilitate the EET via OMC-flavins cofactor, breaking the stereotype of the certain redox state of OMCs at a given potential. As a synergistic effect, EET via both OMCs and flavins is highly boosted simultaneously to achieve the dual-pathway EET, which could be further amplified by the nanostructured topology of the as-prepared electrode. Moreover, the EET current shows a positive correlation with the nanowire length, showing good controllability. This work provides an applicable method for constructing various highly efficient bioelectric devices.