Bioelectrochemical analyses of a thermophilic biocathode catalyzing sustainable hydrogen production

To achieve sustainable hydrogen production by microbial electrolysis cell (MEC) without precious metal catalysts, we examined the potential of thermophilic microorganisms as biocatalysts on the cathode of MEC. A biocathode was firstly developed in a single-chambered MEC operated at 55 °C and further analyzed in a two-chambered MEC. Linear sweep voltammetry showed that the biocathode had a reducing activity significantly higher than the control electrodes (bioanode or non-inoculated electrode). At the potential of −0.8 V vs. SHE, the thermophilic biocathode produced a current density of 1.28 ± 0.15 A m−2 and an H2 production rate of 376.5 ± 73.42 mmol day−1 m−2, which were around 10 times higher than those of the non-inoculated electrode, with the cathodic H2 recovery of ca. 70%. The molecular-phylogenetic analysis of the bacteria on the biocathode indicated that the community was comprised of six phyla, in which Firmicutes was the most populated phylum (77% of the clones in the 16S rRNA library).