Biocathode in microbial electrolysis cell; present status and future prospects

The application of the biocathode for hydrogen production in a Microbial Electrolysis Cell (MEC) is a promising alternative to precious metal catalysts. However, biocathodes are still in the improvement and development stages and require a deep understanding of the bioelectrochemical mechanisms involved. In this review, the results of biocathode MEC experiments and studies in the literature on biocathode development methods were summarised; furthermore, used carbon sources and substrates in biocathodic compartments and microbial communities on the biocathode were characterised. Based on the respective articles that were examined, biocathode MEC may be developed and initiated in one of three categories: (I) half biological two-chambered biocathode MEC; (II) full biological two-chambered biocathode MEC; (III) full biological single-chambered biocathode MEC. In addition, various mixed cultures capable of producing hydrogen were identified, and predominant species were detected. Desulfovibrio paquesii, Desulfovibrio G11 and Geobacter sulfurreducens were also successfully tested as pure cultures in biocathode MECs. Further studies are necessary for an acute and experimental comprehension of the transfer of electrons and the energy conservation mechanism involved in the biocathode MEC, which may provide a cost-effective and practical implementation of this technology.