Efficient CO2 conversion to formic acid in a novel microbial photoelectrochemical cell using a visible-light responsive Co3O4 nanorod-arrayed photocathode

A microbial photoelectrochemical cell (MPEC) is a self-biased, solar-driven device combining bioenergy with solar energy to produce sustainable electricity and chemicals. Here, an MPEC with a p-type Co3O4 nanorod-arrayed photocathode and bio-anode was constructed that matched well the redox potentials of anode microorganisms with the band gap of the Co3O4. The yield of formic acid produced by this MPEC under visible light irradiation with an external resistance of 300 O was 239 +/- 10 mu mol in 10 h, which was 1.8 times that produced by a bare Co3O4 photocathode under visible light, and 4.9 times that produced by the MPEC operated in dark. The maximum power density was 331 +/- 4mW m(-2) under visible light, compared to 175 +/- 25mW m(-2) in the dark. This study of MPEC with the synergistic effect of light energy and bioenergy opens up new opportunities for applications in environmental treatment of wastewaters and chemicals production.