Abstract
Large-scale implementation of (plant) microbial fuel cells is greatly limited by high electrode costs. In this work, the potential of exploiting electrochemically active self-assembled biofilms in fabricating three-dimensional bioelectrodes for (plant) microbial fuel cells with minimum use of electrode materials was studied. Three-dimensional robust bioanodes were successfully developed with inexpensive polyurethane foams (PU) and activated carbon (AC). The PU/AC electrode bases were fabricated via a water-based sorption of AC particles on the surface of the PU cubes. The electrical current was enhanced by growth of bacteria on the PU/AC bioanode while sole current collectors produced minor current. Growth and electrochemical activity of the biofilm were shown with SEM imaging and DNA sequencing of the microbial community. The electric conductivity of the PU/AC electrode enhanced over time during bioanode development. The maximum current and power density of an acetate fed MFC reached 3 mA·m−2 projected surface area of anode compartment and 22 mW·m−3 anode compartment. The field test of the Plant-MFC reached a maximum performance of 0.9 mW·m−2 plant growth area (PGA) at a current density of 5.6 mA·m−2 PGA. A paddy field test showed that the PU/AC electrode was suitable as an anode material in combination with a graphite felt cathode. Finally, this study offers insights on the role of electrochemically active biofilms as natural enhancers of the conductivity of electrodes and as transformers of inert low-cost electrode materials into living electron acceptors.
Highlights
In a bioelectrochemical system (BES) application such as a (Plant) Microbial Fuel Cell, an electrode is a crucial part because of its function to accept released electrons from electrochemically active bacteria in the anode and to transfer the electrons to the final electron acceptor in the cathode [1,2].Especially in plant microbial fuel cells with its relative low current density, large amounts of electrodes are required
8 clearly shows electrodes with the surface and formed wire structures. These observed structures couldthat be the remains of extracellular a biofilm have lowerpart ohmic resistivity compared the clean
Measurement than polyurethane foams (PU)/activated carbon (AC)/BIO II because one sample from PU/AC/BIO I went to microbial analysis
Summary
In a bioelectrochemical system (BES) application such as a (Plant) Microbial Fuel Cell, an electrode is a crucial part because of its function to accept released electrons from electrochemically active bacteria in the anode and to transfer the electrons to the final electron acceptor in the cathode [1,2].Especially in plant microbial fuel cells with its relative low current density, large amounts of electrodes are required. One of the most utilized electrodes is graphite felt [3,4,5,6,7,8,9,10,11,12,13,14,15,16]. The best two week performance of a plant microbial fuel cell (Plant-MFC) utilizing graphite felt both for the anode and the cathode, achieved a power output of 240 mW·m−2 [13]. Graphite felt has shown itself to be a good electrode, its price (around €62 per m2 ) has become an inhibiting factor in real applications [17]. The electrode cost (with graphite felt) for a tubular Plant-MFC is between 30 and 78% of Energies 2020, 13, 574; doi:10.3390/en13030574 www.mdpi.com/journal/energies
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