Effects of applied potential and reactants to hydrogen-producing biocathode in a microbial electrolysis cell
Effects of applied potential and reactants to hydrogen-producing biocathode in a microbial electrolysis cell
Understanding the mechanism of electron transfer between the cathode and microorganisms in cathode biofilms in microbial electrolysis cells (MECs) for hydrogen production is important. In this study, biocathodes of MECs were successfully re-enriched and subjected to different operating parameters: applied potential, sulfate use and inorganic carbon consumption. It was hypothesized that biocathode catalytic activity would be affected by the applied potentials that initiate electron transfer. While inorganic carbon, in the form of bicarbonate, could be a main carbon source for biocathode growth, sulfate could be a terminal electron acceptor and thus reduced to elemental sulfurs. It was found that potentials more negative than -0.8 V (vs. standard hydrogen electrode) were required for hydrogen production by the biocathode. In additional, a maximum hydrogen production was observed at sulfate and bicarbonate concentrations of 288 and 610 mg/L respectively. Organic carbons were found in the cathode effluents, suggesting that microbial interactions probably happen between acetogens and sulfate reducing bacteria (SRB). The hydrogen-producing biocathode was sulfate-dependent and hydrogen production could be inhibited by excessive sulfate because more energy was directed to reduce sulfate (E° SO42-/H2S = -0.35 V) than proton (E° H+/H2 = -0.41 V). This resulted in a restriction to the hydrogen production when sulfate concentration was high. Domestic wastewaters contain low amounts of organic compounds and sulfate would be a better medium to enrich and maintain a hydrogen-producing biocathode dominated by SRB. Besides the risks of limited mass transport and precipitation caused by low potential, methane contamination in the hydrogen-rich environment was inevitable in the biocathode after long term operation due to methanogenic activities.
Bicarbonate conversion, Electron bifurcation, Hydrogen-producing biocathode, Microbial electrolysis cell, Sulfate reduction
Lim, Swee Su
b2f36c85-e9ce-44da-8a8a-0a4d84fa61d4
Kim, Byung Hong
a59d6047-8293-41f5-9cb6-0371ca76092a
Da Li, Li
fddb3b71-b176-4fc4-8713-03a065086db7
Feng, Yujie
c337c8aa-b99d-42d1-9b51-a5521b1e14a0
Wan Daud, Wan Ramli
54644867-114d-4e20-983a-a488a28e8b17
Scott, Keith
38909157-296d-4fe7-a245-1b98e1fee913
Yu, Eileen Hao
28e47863-4b50-4821-b80b-71fb5a2edef2
15 August 2018
Lim, Swee Su
b2f36c85-e9ce-44da-8a8a-0a4d84fa61d4
Kim, Byung Hong
a59d6047-8293-41f5-9cb6-0371ca76092a
Da Li, Li
fddb3b71-b176-4fc4-8713-03a065086db7
Feng, Yujie
c337c8aa-b99d-42d1-9b51-a5521b1e14a0
Wan Daud, Wan Ramli
54644867-114d-4e20-983a-a488a28e8b17
Scott, Keith
38909157-296d-4fe7-a245-1b98e1fee913
Yu, Eileen Hao
28e47863-4b50-4821-b80b-71fb5a2edef2
Lim, Swee Su, Kim, Byung Hong, Da Li, Li, Feng, Yujie, Wan Daud, Wan Ramli, Scott, Keith and Yu, Eileen Hao
(2018)
Effects of applied potential and reactants to hydrogen-producing biocathode in a microbial electrolysis cell.
Frontiers in Chemistry, 6, [318].
(doi:10.3389/fchem.2018.00318).
Abstract
Understanding the mechanism of electron transfer between the cathode and microorganisms in cathode biofilms in microbial electrolysis cells (MECs) for hydrogen production is important. In this study, biocathodes of MECs were successfully re-enriched and subjected to different operating parameters: applied potential, sulfate use and inorganic carbon consumption. It was hypothesized that biocathode catalytic activity would be affected by the applied potentials that initiate electron transfer. While inorganic carbon, in the form of bicarbonate, could be a main carbon source for biocathode growth, sulfate could be a terminal electron acceptor and thus reduced to elemental sulfurs. It was found that potentials more negative than -0.8 V (vs. standard hydrogen electrode) were required for hydrogen production by the biocathode. In additional, a maximum hydrogen production was observed at sulfate and bicarbonate concentrations of 288 and 610 mg/L respectively. Organic carbons were found in the cathode effluents, suggesting that microbial interactions probably happen between acetogens and sulfate reducing bacteria (SRB). The hydrogen-producing biocathode was sulfate-dependent and hydrogen production could be inhibited by excessive sulfate because more energy was directed to reduce sulfate (E° SO42-/H2S = -0.35 V) than proton (E° H+/H2 = -0.41 V). This resulted in a restriction to the hydrogen production when sulfate concentration was high. Domestic wastewaters contain low amounts of organic compounds and sulfate would be a better medium to enrich and maintain a hydrogen-producing biocathode dominated by SRB. Besides the risks of limited mass transport and precipitation caused by low potential, methane contamination in the hydrogen-rich environment was inevitable in the biocathode after long term operation due to methanogenic activities.
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fchem-06-00318
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Accepted/In Press date: 10 July 2018
Published date: 15 August 2018
Keywords:
Bicarbonate conversion, Electron bifurcation, Hydrogen-producing biocathode, Microbial electrolysis cell, Sulfate reduction
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Local EPrints ID: 499205
URI: http://eprints.soton.ac.uk/id/eprint/499205
ISSN: 2296-2646
PURE UUID: 89d0a8c6-1362-42f6-a4b7-a311a216fb18
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Date deposited: 12 Mar 2025 17:31
Last modified: 22 Aug 2025 02:45
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Author:
Swee Su Lim
Author:
Byung Hong Kim
Author:
Li Da Li
Author:
Yujie Feng
Author:
Wan Ramli Wan Daud
Author:
Keith Scott
Author:
Eileen Hao Yu
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