Electrochemical characterization of anodic biofilm development in a microbial fuel cell
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ORIGINAL PAPER
Electrochemical characterization of anodic biofilm development in a microbial fuel cell Edith Martin • Oumarou Savadogo • Serge R. Guiot • Boris Tartakovsky
Received: 26 October 2012 / Accepted: 11 February 2013 / Published online: 26 February 2013 Ó Her Majesty the Queen in Right of Canada 2013
Abstract Electrochemical impedance spectroscopy, cyclic voltammetry, and polarization tests were used to monitor the progress of the anode colonization by electrode-reducing microorganisms in a single-chamber membraneless microbial fuel cell seeded with anaerobic sludge. The electrochemical methods showed that an increase in microbial fuel cell power output coincided with a progressive decrease of the anode internal resistance and a more negative open circuit potential. Two redox systems were observed in cyclic voltammograms shortly after microbial fuel cell startup, while a redox system with a peak around -330 mV (vs. Ag/AgCl) was predominant in the mature biofilm. The redox systems were also dependent on the external resistance chosen for microbial fuel cell operation. This suggests that within the diverse microbial populations several species are capable of electron transfer to the anode, and that the microorganisms with the highest electron transfer rate become predominant. Furthermore, the growth of these electrode-reducing microorganisms can be accelerated by optimizing the microbial fuel cell electrical load. Keywords MFC Anodic biofilm Cyclic voltammetry EIS Internal resistance
E. Martin O. Savadogo Laboratory of Electrochemistry and Energetic Materials, E´cole Polytechnique de Montre´al, Centre-ville, C.P. 6079, Montreal, QC H3C 3A7, Canada E. Martin S. R. Guiot B. Tartakovsky (&) National Research Council of Canada (NRC-EME), 6100 Royalmount Avenue, Montreal, QC H4P 2A2, Canada e-mail: [email protected]
1 Introduction Electricity production in microbial fuel cells (MFCs) relies on microorganisms transferring electrons to the anode through a conductive biofilm matrix, by direct contact with the electrode or by self-produced mediators [1–3]. Upon MFC inoculation, the anode-reducing microorganisms colonize the anode surface forming a biofilm [4, 5]. The rate of biofilm formation and its composition in a MFC seeded with a mixed microbial population depends on a number of factors including operating conditions such as organic load and external resistance [6, 7]. A better understanding of how the anodophilic biofilm is formed can be achieved using electrochemical techniques such as polarization tests (PTs), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) [8–10]. PTs are used by almost every MFC study [11–16] since it provides a simple and convenient tool for comparison between various MFC designs and operating conditions. Polarization and power curves obtained in a PT can be used to measure open circuit voltage (OCV), estimate total internal resistance and the maximal power output of a MFC [17]. Electrode potential measurements against a reference
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