A Comprehensive Review on Oxygen Reduction Reaction in Microbial Fuel Cells

Abstract

The focus of microbial fuel cell research in recent years has been on the development of materials, microbes, and transfer of charges in the system, resulting in a substantial improvement in current density and improved power generation. The cathode is generally recognized as the limiting factor due to its high-distance proton transfer, slow oxygen reduction reaction (ORR), and expensive materials. The heterogeneous reaction determines power generation in MFC. This comprehensive review describes-recent advancements in the development of cathode materials and catalysts associated with ORR. The recent studies indicated the utilization of different metal oxides, the ferrite-based catalyst to overcome this bottleneck. These studies conclude that some cathode materials, in particular, graphene-based conductive polymer composites with non-precious metal catalysts provide substantial benefits for sustainable development in the field of MFCs. Furthermore, it also highlights the potentiality to replace the conventional platinum air cathode for the large-scale production of the next generation of MFCs. It was evident from the experiments that cathode catalyst needs to be blended with conductive carbon materials to make cathode conductive and efficient for ORR. This review discusses various antifouling strategies for cathode biofouling and its effect on the MFC performance. Moreover, it also depicts cost estimations of various catalysts essential for further scale-up of MFC technology.

Evaluation of mixed transition metal (Co, Mn, and Cu) oxide electrocatalysts anchored on different carbon supports for robust oxygen reduction reaction in neutral media

“… 60 The beneficial effect of carbon supports to improve the electrical conductivity of MTMOs or both; leading to enhance the electron transfer and accelerate the ORR kinetics, excellent thermal, mechanical, electrical, and optical properties. The porosity of AC is higher than that of graphene 5,61 with more complex surface chemistry that contains an abundance of reduced oxygen and increased nitrogen functionalities, which could be customized to enhance MTMOs performance for ORR in neutral media. 62,63 …”

“…MO 2(ad) , MO 2(ad) , MO 2 H (ad) , MO (ad) , and MOOH (ad) are the main adsorbed intermediate species on the prepared MTMO electrocatalysts surface that was responsible for all of the ORR dynamics. 5 …”

“… 3,4 In this context, the cathodic electrochemical reduction of oxygen (O 2 ) in microbial fuel cells (MFCs) (as shown in eqn (1) ) has recently gained a remarkable interest, owing to the capability of coupling electrochemical ORR with biological organic matter oxidation to generate an electric current. 5–7 O 2 + 2H 2 O + 4e − → 4OH − …”

“…8,9 Although Pt-based catalysts (as well as other precious metals) have been widely used as cathodic catalysts for ORR to minimize the cathodic overpotential and increase the catalytic current densities; their high cost, weak stability, and scarcity limit their application. 5,10,11 In addition, the sluggish kinetics of ORR in neutral pH with complex multiple electron transfer reactions entails a much higher cathodic overpotential compared to ORR in acidic and alkaline media. 12 Therefore, extensive efforts have been made to explore cost-effective, non-precious ORR electrocatalysts that can efficiently replace noble metal-based electrocatalysts.…”

Microbial Fuel Cell United with Other Existing Technologies for Enhanced Power Generation and Efficient Wastewater Treatment

“…Upscaling and practical applicability of MFCs are difficult due to their numerous disadvantages, as mentioned in further sections. The main disadvantage of an MFC is at the cathode region, where there is a shortage of terminal electron acceptor (TEA), which is considered a rate-limiting factor [5][6][7]. The majority of an MFC's efficiency depends on oxygen available at the cathode as a terminal electron acceptor and its efficient reduction on the cathode surface.…”