Bioelectrochemical hydrogen production with hydrogenophilic dechlorinating bacteria as electrocatalytic agents

Hydrogenophilic dechlorinating bacteria were shown to catalyze H2 production by proton reduction, with electrodes serving as electron donors, either in the presence or in the absence of a redox mediator. In the presence of methyl viologen, Desulfitobacterium- and Dehalococcoides-enriched cultures produced H2 at rates as high as 12.4 μeq/mgVSS (volatile suspended solids)/d, with the cathode set at −450 mV vs. the standard hydrogen electrode (SHE), hence very close to the reversible H+/H2 potential value of −414 mV at pH 7. Notably, the Desulfitobacterium-enriched culture was capable of catalyzing H2 production without mediators at cathode potentials lower than −700 mV. At −750 mV, the H2 production rate with Desulfitobacterium spp. was 13.5 μeq/mgVSS/d (or 16 μeq/cm2/d), nearly four times higher than that of the abiotic controls. Overall, this study suggests the possibility of employing dechlorinating bacteria as hydrogen catalysts in new energy technologies such as microbial electrolysis cells.