Improving conversion efficiency of solar energy to electricity in cyanobacterial PEMFC by high levels of photo-H2 production

In this study, we described an efficient electrical power generating system containing cyanobacterial photo-H2 production and custom-built proton exchange membrane fuel cell (PEMFC). The filamentous N2-fixing cyanobacterium Anabaena cylindrica was used as the photo-H2 producer. A photosynthesis inhibitor-diuron (DCMU) was used for the enhancement of photo-H2 production in the culture under argon gas. For the first time, a total of 1.0 μM DCMU was found to be the most effective treatment, as this produced 3.6 fold higher levels of H2 in microalgae. By measuring polarization curve, the gas mixture collected from the culture was proven to be an effective fuel for electrical generation through a custom-built PEMFC. When the PEMFC was directly combined with the culture tube, the cells generated as much as 843 mV during a 5-day incubation due to the efficient conversion of solar energy to H2 by A. cylindrica. Light energy conversion efficiency (LCE) for both solar energy to H2 and solar energy to electricity were also determined. The LCE for the cyanobacterial conversion of solar energy to H2 reached a peak at four days with a maximal value of 2.05% and an average value of 1.70% ± 0.17. The corresponding LCE for the conversion of solar energy to electricity in this system was 1.13% at peak and 0.94% ± 0.09 on average.