Nanorod CoFe2O4 modified activated carbon as an efficient electrocatalyst to improve the performance of air cathode microbial fuel cell

Co-Fe-N@biochar anode for improvment the electricity generation performance of microbial fuel cell

Microbial fuel cells (MFCs) can generate energy while processing organic pollutants, which has a great impact on environmental wastewater treatment applications. In this study, a gel polymer was formed by Co-Fe-N co-doping biochar (Co-Fe-N@BC), which was used as the anode material to improve the electricity generation performance of MFC. The Co-Fe-N@BC material prepared at 900℃ carbonised biomass into more graphitic carbon, and its total resistance (3.56 Ω) was significantly reduced. In the corresponding dual-chamber MFC, the current density was 2.81 A/m2, and the power density reached 1181 mW/m2 at maximum. Among the materials tested, the Co-Fe-N@BC anode MFC had the highest chemical oxygen demand removal rate and coulombic efficiency, reaching 91% and 13%, respectively. It is proved that MFC with Co-Fe-N@BC anode has the best electrochemical performance.

Bimetal-organic framework-derived porous CoFe2O4 nanoparticles as biocompatible anode electrocatalysts for improving the power generation of microbial fuel cells

HYPOTHESIS

The relatively lower power density of Microbial fuel cells (MFCs), primarily resulting from weak biofilm habitation and sluggish extracellular electron transfer (EET) at the anode interface, limits their practical implementation on a large scale. To address this challenge, porous CoFe₂O₄ nanoparticles could be used as anode electrocatalysts based on the following considerations: (i) the introduction of CoFe₂O₄ nanoparticles endows the anode with a rough surface that facilitates biofilm formation; (ii) the positively charged Co and Fe ions improve the interfacial affinity of anodes, enabling rapid immobilization and colonization of negatively bacteria; (iii) the multi-valent metal states of Co and Fe can function as electron shuttles, mediating EET process between biofilm and anode.

EXPERIMENTS

CoFe₂O₄ nanoparticles prepared with a bimetal-organic framework (B-MOF) as precursor, were modified to the surface of carbon cloth as the anode of MFCs.

FINDINGS

MFCs equipped with CoFe₂O₄ anode achieved a maximum power density of 1026.68 mW m^-2, which was approximately 3.4 times higher than that of the pristine carbon cloth. Additionally, the biofilm density and viability on the anode were enhanced after CoFe₂O₄ modification. Considering the facile fabrication process and superior electrocatalytic performance, the CoFe₂O₄ nanoparticles are promising electrocatalysts for high performance and cost-effective MFCs.

Improved bioelectrochemical performance of MnO2 nanorods modified cathode in microbial fuel cell

The property of cathode in the microbial fuel cell (MFC) was one of the key factors limiting its output performance. MnO₂ nanorods were prepared by a simple hydrothermal method as cathode catalysts for MFCs. There were a number of typical characteristic crystal planes of MnO₂ nanorods like (110), (310), (121), and (501). Additionally, there were great many hydroxyl groups on the surface of nanorod-like MnO₂, which provided a rich set of active adsorption sites. The maximum power density (P_max) of MnO₂-MFC was 180 mW/m², which was 1.51 times that of hydrothermally synthesized MnO₂ (119.07 mW/m²), 4.28 times that of naturally synthesized MnO₂ (42.05 mW/m²), and 5.61 times that of the bare cathode (32.11 mW/m²). The maximum voltage was 234 mV and the maximum stabilization time was 4 days. The characteristics of MnO₂, including rod-like structure, high specific surface area, and high conductivity, were conducive to providing more active sites for oxygen reduction reaction (ORR). Therefore, the air cathode modified by MnO₂ nanorods was a kind of fuel cell electrode with great application potential.

Innovative Cost-Effective Nano-NiCo2O4 Cathode Catalysts for Oxygen Reduction in Air-Cathode Microbial Electrochemical Systems

Microbial electrochemical systems (MESs) can harvest bioelectricity from varieties of organic matter in wastewater through electroactive microorganisms. Oxygen reduction reaction (ORR) in a cathode plays an important role in guaranteeing high power generation, which can be enhanced by cathode catalysts. Herein, the tiny crystalline grain nanocrystal NiCo₂O₄ is prepared via the economic method and utilized as an effective catalyst in air-cathode MESs. The linear sweep voltammetry results indicate that the current density of 2% nano-NiCo₂O₄/AC cathode (5.05 A/m²) at 0 V increases by 20% compared to the control (4.21 A/m²). The cyclic voltammetries (CVs) and the electrochemical impedance spectroscopy (EIS) showed that the addition of nano-NiCo₂O₄ (2%) is efficient in boosting the redox activity. The polarization curves showed that the MESs with 2% nano-NiCo₂O₄/AC achieved the highest maximum power density (1661 ± 28 mW/m²), which was 1.11 and 1.22 times as much as that of AC and 5% nano-NiCo₂O₄. Moreover, the adulteration of nano-NiCo₂O₄ with a content of 2% can not only enable the electrical activity of the electrode to be more stable, but also reduce the cost for the same power generation in MESs. The synthetic nano-NiCo₂O₄ undoubtedly has great benefits for large-scale MESs in wastewater treatment.

An overview in the development of cathode materials for the improvement in power generation of microbial fuel cells

Since the high cost and low power generation hinder the overall practical application of microbial fuel cells (MFCs), numerous attempts have been made in the field of cathode materials to enhance the electrical performance of MFCs because they directly catalyze the oxygen reduction reactions (ORR). To choose a proper cathode material, following principles such as ORR activity, conductivity, cost-efficiency, durability, surface area, and accessibility should be taken into consideration. In preparation of cathode materials, versatile materials have been chosen, synthesized, or modified to achieve an improvement in power generation of MFCs. The most widely applied cathode materials could be categorized into three classes, namely carbon-base materials, metal-based materials, and biocatalysts. This review summarizes the utilization, development, and the cost of cathode materials applied in MFCs and tries to highlight the effective modification methods of cathode materials which have helped in achieving enhanced power generation of MFCs in recent years.