Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs)

Wang, Xi; Cheng, Shaoan; Zhang, Xiaoyuan; Li, Xiao-yan; Logan, Bruce E.

Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs)

Type

Article

Authors

Wang, Xi
Cheng, Shaoan
Zhang, Xiaoyuan

Li, Xiao-yan
Logan, Bruce E.

KAUST Grant Number

KUS-I1-003-13

Date

2011-10

Abstract

Several alternative cathode catalysts have been proposed for microbial fuel cells (MFCs), but effects of salinity (sodium chloride) on catalyst performance, separate from those of conductivity on internal resistance, have not been previously examined. Three different types of cathode materials were tested here with increasingly saline solutions using single-chamber, air-cathode MFCs. The best MFC performance was obtained using a Co catalyst (cobalt tetramethoxyphenyl porphyrin; CoTMPP), with power increasing by 24 ± 1% to 1062 ± 9 mW/m2 (normalized to the projected cathode surface area) when 250 mM NaCl (final conductivity of 31.3 mS/cm) was added (initial conductivity of 7.5 mS/cm). This power density was 25 ± 1% higher than that achieved with Pt on carbon cloth, and 27 ± 1% more than that produced using an activated carbon/nickel mesh (AC) cathode in the highest salinity solution. Linear sweep voltammetry (LSV) was used to separate changes in performance due to solution conductivity from those produced by reductions in ohmic resistance with the higher conductivity solutions. The potential of the cathode with CoTMPP increased by 17-20 mV in LSVs when the NaCl addition was increased from 0 to 250 mM independent of solution conductivity changes. Increases in current were observed with salinity increases in LSVs for AC, but not for Pt cathodes. Cathodes with CoTMPP had increased catalytic activity at higher salt concentrations in cyclic voltammograms compared to Pt and AC. These results suggest that special consideration should be given to the type of catalyst used with more saline wastewaters. While Pt oxygen reduction activity is reduced, CoTMPP cathode performance will be improved at higher salt concentrations expected for wastewaters containing seawater. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Citation

Wang X, Cheng S, Zhang X, Li X, Logan BE (2011) Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs). International Journal of Hydrogen Energy 36: 13900–13906. Available: http://dx.doi.org/10.1016/j.ijhydene.2011.03.052.

Acknowledgements

We thank Gilbert Van Bogaert and Deepak Pant of VITO, for donating the activated carbon cathodes used in this study. This research was supported in part by Award KUS-I1-003-13 from the King Abdullah University of Science and Technology (KAUST), the US National Science Foundation (CBET-0730359), and URC funding from the University of Hong Kong.