A self-recirculation electrolyte system for unbuffered microbial fuel cells with an aerated cathode

LiangZhanga, XunZhua, JunLia, QianFua, YanLib, YuanxinLi

Key Laboratory of Low-grade Energy Utilization Technologies and Systems (Chongqing University), Ministry of Education, Chongqing 40003, China.

Abstract

A self-recirculation electrolyte system driven by air bubble buoyancy force is proposed for unbuffered microbial fuel cells (MFC) in this study. It was demonstrated that the electrolyte recirculation rate increased with the aeration rate in a certain range. Compared with buffer condition, buffer-less condition resulted in a 10% ∼ 20% lower voltage (14.2% lower maximum power density) but a 9.1% higher Coulombic efficiency (CE) at an aeration rate of 92.0 ml/min. Under buffer-less condition, increasing the aeration rate resulted in a higher voltage output, a higher COD removal, and a higher CE due to the enhanced proton transfer and increased oxygen for cathode reaction. However, an extra high aeration rate induced a rapid deterioration of anode performance due to the excessive oxygen transfer into anode. This study demonstrates that the self-recirculation electrolyte system could be helpful for future unbuffered MFC designs.

Graphical abstract