title: Photoenhanced electrochemical interaction between Shewanella and a hematite nanowire photoanode.
abstract: Here we report the investigation of interplay between light, a hematite nanowire-arrayed photoelectrode, and Shewanella oneidensis MR-1 in a solar-assisted microbial photoelectrochemical system (solar MPS). Whole cell electrochemistry and microbial fuel cell (MFC) characterization of Shewanella oneidensis strain MR-1 showed that these cells cultured under (semi)anaerobic conditions expressed substantial c-type cytochrome outer membrane proteins, exhibited well-defined redox peaks, and generated bioelectricity in a MFC device. Cyclic voltammogram studies of hematite nanowire electrodes revealed active electron transfer at the hematite/cell interface. Notably, under a positive bias and light illumination, the hematite electrode immersed in a live cell culture was able to produce 150% more photocurrent than that in the abiotic control of medium or dead culture, suggesting a photoenhanced electrochemical interaction between hematite and Shewanella. The enhanced photocurrent was attributed to the additional redox species associated with MR-1 cells that are more thermodynamically favorable to be oxidized than water. Long-term operation of the hematite solar MPS with light on/off cycles showed stable current generation up to 2 weeks. Fluorescent optical microscope and scanning electron microscope imaging revealed that the top of the hematite nanowire arrays were covered by a biofilm, and iron determination colorimetric assay revealed 11% iron loss after a 10-day operation. To our knowledge, this is the first report on interfacing a photoanode directly with electricigens in a MFC system. Such a system could open up new possibilities in solar-microbial device that can harvest solar energy and recycle biomass simultaneously to treat wastewater, produce electricity, and chemical fuels in a self-sustained manner.
authors.affiliation: Physical and Life Sciences Directorate, Lawrence Livermore National Laboratories , Livermore, California 94550, United States.
authors.forename: Fang
authors.initials: F
authors.lastname: Qian
authors.forename: Hanyu
authors.initials: H
authors.lastname: Wang
authors.forename: Yichuan
authors.initials: Y
authors.lastname: Ling
authors.forename: Gongming
authors.initials: G
authors.lastname: Wang
authors.forename: Michael P
authors.initials: MP
authors.lastname: Thelen
authors.forename: Yat
authors.initials: Y
authors.lastname: Li
mesh_terms: D001674:Bioelectric Energy Sources; D018441:Biofilms; D004566:Electrodes; D005290:Ferric Compounds / Q000737:chemistry*; D008027:Light; D053770:Nanowires / Q000737:chemistry*; D020592:Shewanella / Q000502:physiology*
chemical_list: D005290:Ferric Compounds; C000499:ferric oxide