Highly efficient cathode for the microbial fuel cell using LaXO3 (X = [Co, Mn, Co0.5Mn0.5]) perovskite nanoparticles as electrocatalysts

Multi-metal ferrite as a promising catalyst for oxygen reduction reaction in microbial fuel cell

Improving catalytic activity of cathode with noble metal-free catalysts can significantly establish microbial fuel cells (MFCs) as a sustainable and economically affordable technology. This investigation aimed to assess the viability of utilizing tri-metal ferrite (Co0.5Cu0.5 Bi0.1Fe1.9O4) as an oxygen reduction reaction (ORR) catalyst to enhance the performance of cathode in MFCs. Trimetallic ferrite was synthesized using a sol-gel auto-combustion process. Electrochemical evaluations were conducted to assess the efficacy of as-synthesized composite as an ORR catalyst, employing electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). This evaluation revealed that the impregnation of bismuth in the Co-Cu-ferrite structure improves the reduction current response and reduces the charge transfer resistance. Further experiments were conducted to test the performance of this catalyst in an MFC. The MFC with tri-metal ferrite catalyst generated a power density of 11.44 W/m3 with 21.4% coulombic efficiency (CE), which was found to be comparable with commercially available 10% Pt/C used as cathode catalyst in MFC (power density of 12.14 W/m3 and CE of 23.1%) and substantially greater than MFC having bare carbon felt cathode without any catalyst (power density of 2.49 W/m3 and CE of 7.39%). This exceptionally inexpensive ORR catalyst has adequate merit to replace commercial costlier platinum-based cathode catalysts for upscaling MFCs.

Enhancing the efficiency of medium-scale dual-chamber microbial fuel cell systems through the utilization of novel electrodes material and proper selection of catholyte and external resistance

Dual-chamber microbial fuel cells (DC-MFC) are devices that can be used to generate electricity through the degradation of substrates. In this study, the performance of DC-MFC with novel electrode materials is evaluated under different external resistance using a hydrochloric acid solution as catholyte. Hydrophilic-treated graphene was used as the electrode material, DuPontTM Nafion 117 was used as the proton exchange membrane and domestic wastewater served as the substrate. The maximum power density achieved was 32.05 m W ⋅ m - 2 , obtained by degrading 69.8% of organic matter when an external resistance of 100 Ω was used as electrical load. This power density was 32 times higher than the power density obtained in the control (1.01 m W ⋅ m - 2 ). This result obtained was similar to those reported in the literature for small-scale DC-MFC systems. And, contrary to the reported trend that as the scale of MFCs increase, the efficiency decreases. It can be stipulated with these results that is possible to scale up DC-MFC to medium-scale systems without loss performance quality by selecting the appropriate external resistance, catholyte and electrode materials.

Contribution of configurations, electrode and membrane materials, electron transfer mechanisms, and cost of components on the current and future development of microbial fuel cells

Microbial fuel cells (MFCs) are a technology that can be applied to both the wastewater treatment and bioenergy generation. This work discusses the contribution of improvements regarding the configurations, electrode materials, membrane materials, electron transfer mechanisms, and materials cost on the current and future development of MFCs. Analysis of the most recent scientific publications on the field denotes that dual-chamber MFCs configuration offers the greatest potential due to the excellent ability to be adapted to different operating environments. Carbon-based materials show the best performance, biocompatibility of carbon-brush anode favors the formation of the biofilm in a mixed consortium and in wastewater as a substrate resembles the conditions of real scenarios. Carbon-cloth cathode modified with nanotechnology favors the conductive properties of the electrode. Ceramic clay membranes emerge as an interesting low-cost membrane with a proton conductivity of 0.0817 S cm^-1, close to that obtained with the Nafion membrane. The use of nanotechnology in the electrodes also enhances electron transfer in MFCs. It increases the active sites at the anode and improves the interface with microorganisms. At the cathode, it favors its catalytic properties and the oxygen reduction reaction. These features together favor MFCs performance through energy production and substrate degradation with values above 2.0 W m^-2 and 90% respectively. All the recent advances in MFCs are gradually contributing to enable technological alternatives that, in addition to wastewater treatment, generate energy in a sustainable manner. It is important to continue the research efforts worldwide to make MFCs an available and affordable technology for industry and society.

Perovskite-Based Nanocomposite Electrocatalysts: An Alternative to Platinum ORR Catalyst in Microbial Fuel Cell Cathodes

Microbial fuel cells (MFCs) are biochemical systems having the benefit of producing green energy through the microbial degradation of organic contaminants in wastewater. The efficiency of MFCs largely depends on the cathode oxygen reduction reaction (ORR). A preferable ORR catalyst must have good oxygen reduction kinetics, high conductivity and durability, together with cost-effectiveness. Platinum-based electrodes are considered a state-of-the-art ORR catalyst. However, the scarcity and higher cost of Pt are the main challenges for the commercialization of MFCs; therefore, in search of alternative, cost-effective catalysts, those such as doped carbons and transition-metal-based electrocatalysts have been researched for more than a decade. Recently, perovskite-oxide-based nanocomposites have emerged as a potential ORR catalyst due to their versatile elemental composition, molecular mechanism and the scope of nanoengineering for further developments. In this article, we discuss various studies conducted and opportunities associated with perovskite-based catalysts for ORR in MFCs. Special focus is given to a basic understanding of the ORR reaction mechanism through oxygen vacancy, modification of its microstructure by introducing alkaline earth metals, electron transfer pathways and the synergistic effect of perovskite and carbon. At the end, we also propose various challenges and prospects to further improve the ORR activity of perovskite-based catalysts.

Simultaneous Investigation of Three Effective Parameters of Substrate, Microorganism Type and Reactor Design on Power Generation in a Dual-Chamber Microbial Fuel Cells

BACKGROUND

The use of Microbial Fuel Cells (MFCs) has been expanded in recent years due to their ability in producing bioelectricity and treating wastewater simultaneously. However, there are still some obstacles to use MFC on an industrial scale. Regardless of the restriction of electrodes applied in the electron transferring process, there are also some other factors having strong roles in reducing the power density of MFCs.

OBJECTIVES

In this paper, the effect of three categories of limiting factors such as kinds of microorganisms (Saccharomyces cerevisiae and Shewanella sp.), substrate type (Glucose and acetate), and features reactor components have been investigated on the power density generation. Simultaneous investigation of these parameters and demonstration of which parameters would induce more power density can help to improve the scale‑up of MFCs.

MATERIALS AND METHODS

Two types of MFCs with different designs were constructed and inoculated with pure cultures of Saccharomyces cerevisiae PTCC 5269 and Shewanella sp. The OCV (Open Circuit Voltage) and polarization curves of MFCs were measured when the quasi‑steady‑state condition was observed.

RESULTS

Based on results, utilizing acetate in the presence of both microorganisms led to approximately 60% higher power density compared to glucose. The comparison of maximum power densities of different reactor designs indicated an approximately 17-70 % increase of power generation. However, the resultant shows modification of reactor design even when other parameters are not optimal can increase power density more than three times.

CONCLUSION

Actually, reactor design has the most important role in the power density with the MFC while the effects of substrate and microorganism parameters are not inappreciable.