Photoenhanced Electrochemical Interaction between <i>Shewanella</i> and a Hematite Nanowire Photoanode
- Publication date
- Publisher
Abstract
Here we report the investigation
of interplay between
light, a
hematite nanowire-arrayed photoelectrode, and <i>Shewanella oneidensis</i> MR-1 in a solar-assisted microbial photoelectrochemical system (solar
MPS). Whole cell electrochemistry and microbial fuel cell (MFC) characterization
of <i>Shewanella oneidensis</i> strain MR-1 showed that
these cells cultured under (semi)anaerobic conditions expressed substantial <i>c</i>-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 <i>Shewanella</i>. 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