Abstract
In the past 20 years Microbial fuel cells (MFCs) have been extensively studied regarding the possibility of transforming organic waste directly into electricity. There are significant differences between MFCs and conventional low temperature Fuel Cells (FCs), which make MFCs attractive: biotic catalyst at the anode; the anodic fuel is complex organic waste; MFCs operate under mild reaction conditions (neutral pH, temperature and pressure), close to ambient levels as optimum. Like chemical fuel cells, MFCs are composed of anode and cathode. Oxygen is an ideal electron acceptor for MFCs because of its high redox potential, availability, and sustainability. However, the Oxygen Reduction Reaction (ORR) is kinetically sluggish, resulting in a large proportion of potential loss. Also, working conditions are quite different because of the type of complex media in which MFCs operate. In order to overcome these limitations, catalysts are often used to lower the overpotentials and accelerate the kinetics of the oxygen reduction reaction. One of the main challenges is the development of efficient and stable cathode catalysts for MFCs. By far, Pt and Pt-based catalysts (PGMs) have been extensively used, due to their catalytic efficiency in gas-diffusion electrodes. But the high cost and low durability have significantly lowered their utilization in MFCs. A variety of non-precious metal catalysts have been developed for MFC applications including carbon-based catalysts, carbon supported composite catalysts, Me-based catalysts and biocatalysts. It is supposed that the ORR catalyst used for wastewater treatment in MFCs is simple to synthesize, cost-effective, durable after long-term operation in wastewater, tolerant to poisoning and able to restore catalytic activity after cleaning. In this regard carbon-based catalyst may be the most promising candidate for practical applications. This study reviews different carbon-based ORR catalysts for MFC applications for wastewater treatment and energy recovery.
Highlights
In the past 20 years Microbial fuel cells have been extensively studied with regard to the possibility of transforming organic waste directly into electricity [1, 2, 3, 4, 5, 6]
Platinum group metal free (PGM-free) catalysts have been developed for cathodic materials in the Microbial fuel cells (MFCs) that are resistant to poisoning in wastewater, activated sludge and other organics / pollutants [17, 18]
In our previous work [29] we have investigated the influence of different carbon blacks on the properties of air gas-diffusion electrodes with respect to their application as cathode materials in meal-air systems
Summary
In the past 20 years Microbial fuel cells have been extensively studied with regard to the possibility of transforming organic waste directly into electricity [1, 2, 3, 4, 5, 6]. Pt and Pt-based catalysts (named as Platinum Group Metals (PGMs) have been extensively used catalysts in the initial stages of developing cathode materials for MFCs, due to their catalytic efficiency in gas-diffusion electrodes used in acidic and alkaline Fuel cells. Platinum group metal free (PGM-free) catalysts have been developed for cathodic materials in the MFC that are resistant to poisoning in wastewater, activated sludge and other organics / pollutants [17, 18].
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