The importance of OH − transport through anion exchange membrane in microbial electrolysis cells

Handle URI:
http://hdl.handle.net/10754/626998
Title:
The importance of OH − transport through anion exchange membrane in microbial electrolysis cells
Authors:
Ye, Yaoli; Logan, Bruce E. ( 0000-0001-7478-8070 )
Abstract:
In two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact electrochemical performance. However, ion transport between the chambers will also impact performance, which is a factor not included in those calculations. To separate the impacts of pH and ion transport on MEC performance, a high molecular weight polymer buffer (PoB), which was retained in the catholyte due to its low AEM transport and cationic charge, was compared to PBS in MECs and abiotic electrochemical half cells (EHCs). In MECs, catholyte pH control was less important than ion transport. MEC tests using the PoB catholyte, which had a higher buffer capacity and thus maintained a lower catholye pH (<8), resulted in a 50% lower hydrogen production rate (HPR) than that obtained using PBS (HPR = 0.7 m3-H2 m−3 d−1) where the catholyte rapidly increased to pH = 12. The main reason for the decreased performance using PoB was a lack of hydroxide ion transfer into the anolyte to balance pH. The anolyte pH in MECs rapidly decreased to 5.8 due to a lack of hydroxide ion transport, which inhibited current generation by the anode, whereas the pH was maintained at 6.8 using PBS. In abiotic tests in ECHs, where the cathode potential was set at −1.2 V, the HPR was 133% higher using PoB than PBS due to catholyte pH control, as the anolyte pH was not a factor in the performance. These results show that maintaining charge transfer to control anolyte pH is more important than obtaining a more neutral pH catholyte.
Citation:
Ye Y, Logan BE (2018) The importance of OH − transport through anion exchange membrane in microbial electrolysis cells. International Journal of Hydrogen Energy. Available: http://dx.doi.org/10.1016/j.ijhydene.2017.12.074.
Publisher:
Elsevier BV
Journal:
International Journal of Hydrogen Energy
KAUST Grant Number:
OSR-2015-SEED-2450-01
Issue Date:
11-Jan-2018
DOI:
10.1016/j.ijhydene.2017.12.074
Type:
Article
ISSN:
0360-3199
Sponsors:
This work was supported by Award OSR-2015-SEED-2450-01 from the King Abdullah University of Science and Technology (KAUST).
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorYe, Yaolien
dc.contributor.authorLogan, Bruce E.en
dc.date.accessioned2018-02-01T08:12:00Z-
dc.date.available2018-02-01T08:12:00Z-
dc.date.issued2018-01-11en
dc.identifier.citationYe Y, Logan BE (2018) The importance of OH − transport through anion exchange membrane in microbial electrolysis cells. International Journal of Hydrogen Energy. Available: http://dx.doi.org/10.1016/j.ijhydene.2017.12.074.en
dc.identifier.issn0360-3199en
dc.identifier.doi10.1016/j.ijhydene.2017.12.074en
dc.identifier.urihttp://hdl.handle.net/10754/626998-
dc.description.abstractIn two-chamber microbial electrolysis cells (MECs) with anion exchange membranes (AEMs), a phosphate buffer solution (PBS) is typically used to avoid increases in catholyte pH as Nernst equation calculations indicate that high pHs adversely impact electrochemical performance. However, ion transport between the chambers will also impact performance, which is a factor not included in those calculations. To separate the impacts of pH and ion transport on MEC performance, a high molecular weight polymer buffer (PoB), which was retained in the catholyte due to its low AEM transport and cationic charge, was compared to PBS in MECs and abiotic electrochemical half cells (EHCs). In MECs, catholyte pH control was less important than ion transport. MEC tests using the PoB catholyte, which had a higher buffer capacity and thus maintained a lower catholye pH (<8), resulted in a 50% lower hydrogen production rate (HPR) than that obtained using PBS (HPR = 0.7 m3-H2 m−3 d−1) where the catholyte rapidly increased to pH = 12. The main reason for the decreased performance using PoB was a lack of hydroxide ion transfer into the anolyte to balance pH. The anolyte pH in MECs rapidly decreased to 5.8 due to a lack of hydroxide ion transport, which inhibited current generation by the anode, whereas the pH was maintained at 6.8 using PBS. In abiotic tests in ECHs, where the cathode potential was set at −1.2 V, the HPR was 133% higher using PoB than PBS due to catholyte pH control, as the anolyte pH was not a factor in the performance. These results show that maintaining charge transfer to control anolyte pH is more important than obtaining a more neutral pH catholyte.en
dc.description.sponsorshipThis work was supported by Award OSR-2015-SEED-2450-01 from the King Abdullah University of Science and Technology (KAUST).en
dc.publisherElsevier BVen
dc.subjectHydrogenen
dc.subjectMicrobial electrolysis cellen
dc.subjectAnion exchange membraneen
dc.subjectAnolyte pHen
dc.subjectBuffer retentionen
dc.subjectPolymeric bufferen
dc.titleThe importance of OH − transport through anion exchange membrane in microbial electrolysis cellsen
dc.typeArticleen
dc.identifier.journalInternational Journal of Hydrogen Energyen
dc.contributor.institutionDepartment of Civil and Environmental Engineering, The Pennsylvania State University, University Park, PA, 16802, USAen
kaust.grant.numberOSR-2015-SEED-2450-01en
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