Evaluation of Microbial Fuel Cells with Graphite Plus MnO₂and MoS₂Paints as Oxygen Reduction Cathode Catalyst

Abstract

For the improvement of microbial fuel cell (MFC) performance in real wastewater it is necessary to implement catalysts on the cathode. Potential electrochemical catalysts for the MFC have to be widely available and should be low cost materials. Graphite, MnO 2 and MoS 2 fulfill the requirements and were evaluated in this work. These materials were prepared by dispersion of MnO 2 and/or MoS 2 and graphite in a solution of celluloid using butanone as solvent. Four MFCs with an active area of 225 cm 2 were connected in series with the wastewater supply. Their individual maximum output power densities were evaluated in relation to time. The results showed that MFC without catalyst reached a power density of only 40 mW/m 2 , while the best performance of MFC with graphite plus MnO 2 coating (10:1) was higher than 100 mW/m 2 . Comparing with graphite plus MnO 2 coating, the graphite plus MoS 2 paint shows a lower power density but much higher long-term stability than graphite plus MnO 2 coating. The scaling up of MFC with catalyst on the cathode is also studied in this research. Four MFCs with dimension of 980 cm 2 were constructed and connected in series, whose anodes have two sides for enlargement of reaction surface area. Rising demand for energy and fossil fuel resources being finite, the search for new alternative sustainable energy solutions have increased tremendously.1 Hydraulic, wind and solar radiation are clean energy resources as alternatives to fossil resources to produce electricity. However, these energy sources are limited by climate and geographical factors. Comparing with the energy sources that are mentioned above, biomass is one of the important renewable carbon sources and has been recognized as a promising energy supplier in the future. The increasing demand for biofuels has encouraged researchers and politicians worldwide to find sustainable biofuel production systems in accordance with the regional conditions and needs. 2 A MFC is an innovative method to generate electricity from organic matter using exoelectrogenic bacteria.3 Furthermore MFCs have drawn increasing attention as they can generate renewable energy and purify wastewater simultaneously. 4 The main MFC-components are the electrodes, separated into the anodic-and cathodic-chamber. Electrons and protons are produced on the anode from the oxidation of organic matters using bacteria as biocatalyst. In the cathode chamber, an electron acceptor is reduced with the electrons transferred via an external circuit and the protons diffused through the solution. However, complete treatment of wastewater cannot be accomplished solely with MFCs as current production is rapidly reduced to low levels when the chemical oxygen demand of the organic matter is reduced to ∼100-200 mg/L. 6,7 Scaling up MFCs is challenging based on the need to use inexpensive and non-precious metal materials and to achieve good performance. The use of carbon fiber brushes provides a route to make low-cost anodes, [8][9][10] and several different cathodes have been construc...

Electrochemical Reactors for Wastewater Treatment

“…Since the cathode is often the limiting electrode in an MFC, new, inexpensive, and non‐toxic catalysts for oxygen reduction are under development. So far, different graphites, platinum, and manganese dioxide have been investigated , .…”

Elektrochemische Reaktoren für die Wasserbehandlung

“…Für [90,91] Aus den geringen Spannungen und Stromdichten der MBZ ergeben sich im Vergleich zu klassischen, rein chemischen Brennstoffzellen sehr geringe Leistungsdichten von ca. maximal 1 W m -2 [92], weshalb u. a. bisher noch kein kommerzieller Erfolg der mikrobiellen Brennstoffzelle verzeichnet wurde.…”

Bimetallic platinum group metal-free catalysts for high power generating microbial fuel cells

“…Usually, the earth abundant transitional metal is atomically dispersed within a carbonaceous substrate rich in nitrogen. Several PGM-free catalysts were presented in literature, and particularly, catalysts based on iron [67], [68], [69], [70], [71], [72], [73], [74], [75], cobalt [76], [77], [78], [79], manganese [80], [81], [82], nickel [83], [84], etc [85], [86] have been investigated as cathode catalysts in the ORR reaction. Among these earth abundant metals, iron and cobalt are particularly alluring due to their higher performances compared to Mn, Ni and al [1], [87], [88].…”