TY - JOUR
T1 - Reduced overpotentials in microbial electrolysis cells through improved design, operation, and electrochemical characterization
AU - Ki, Dongwon
AU - Popat, Sudeep C.
AU - Torres, Cesar
N1 - Funding Information:
We acknowledge the Office of Naval Research (grant # N00014121034 ) and the Department of Defense’s SERDP program (project # ER-2239) for providing the funding for this study.
Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2016/3/1
Y1 - 2016/3/1
N2 - One of the main performance challenges in microbial electrochemical cells (MXCs) is the low voltage efficiency in comparison to other fuel and electrolysis cells. In this study, we aimed to improve the design and operation of microbial electrolysis cells (MECs) to achieve current densities >10Am-2 with reduced applied voltages, using a thorough analytical framework involving electrochemical techniques such as chronoamperometry, voltammetry and electrochemical impedance spectroscopy. We developed a design that allows high surface area for the anode using carbon fibers, but without creating a large distance between the anode and the cathode (<0.5cm) to reduce Ohmic overpotential. We determined that Ohmic overpotential, at current densities >10Am-2 remained <0.1V even when using an anion exchange membrane to separate the anode and the cathode. We observed the largest overpotential from cathode related phenomena. The increase in pH in the cathode chamber, often to ~13, results in >0.3V of Nernstian concentration overpotential. We showed how by adding CO2 to the cathode, this overpotential could be reduced to negligible. We also tested two different cathode materials - stainless steel and nickel - to compare the cathode activation overpotentials. Overall, through our design and operation improvements, we were able to reduce the applied voltages from 1.1 to ~0.85V, at 10 Am-2. Our results also provide important guidelines for further optimizations of MXCs.
AB - One of the main performance challenges in microbial electrochemical cells (MXCs) is the low voltage efficiency in comparison to other fuel and electrolysis cells. In this study, we aimed to improve the design and operation of microbial electrolysis cells (MECs) to achieve current densities >10Am-2 with reduced applied voltages, using a thorough analytical framework involving electrochemical techniques such as chronoamperometry, voltammetry and electrochemical impedance spectroscopy. We developed a design that allows high surface area for the anode using carbon fibers, but without creating a large distance between the anode and the cathode (<0.5cm) to reduce Ohmic overpotential. We determined that Ohmic overpotential, at current densities >10Am-2 remained <0.1V even when using an anion exchange membrane to separate the anode and the cathode. We observed the largest overpotential from cathode related phenomena. The increase in pH in the cathode chamber, often to ~13, results in >0.3V of Nernstian concentration overpotential. We showed how by adding CO2 to the cathode, this overpotential could be reduced to negligible. We also tested two different cathode materials - stainless steel and nickel - to compare the cathode activation overpotentials. Overall, through our design and operation improvements, we were able to reduce the applied voltages from 1.1 to ~0.85V, at 10 Am-2. Our results also provide important guidelines for further optimizations of MXCs.
KW - Design
KW - Microbial electrolysis cells
KW - Microbial fuel cells
KW - Operation
KW - Overpotential
KW - Voltage efficiency
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U2 - 10.1016/j.cej.2015.11.022
DO - 10.1016/j.cej.2015.11.022
M3 - Article
AN - SCOPUS:84947983476
SN - 1385-8947
VL - 287
SP - 181
EP - 188
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
ER -