Improved power generation using nitrogen-doped 3D graphite foam anodes in microbial fuel cells

Enhanced electroactive bacteria enrichment and facilitated extracellular electron transfer in microbial fuel cells via polydopamine coated graphene aerogel anode

The structure and surface physicochemical properties of anode play a crucial role in microbial fuel cells (MFCs). To enhance the enrichment of exoelectrogen and facilitate extracellular electron transfer (EET), a three-dimensional macroporous graphene aerogel with polydopamine coating was successfully introduced to modify carbon brush (PGA/CB). The three-dimensional graphene aerogel (GA) with micrometer pores improved the space utilization efficiency of microorganisms. Polydopamine (PDA) coating enhanced the physicochemical properties of the electrode surface by introducing abundant functional groups and nitrogen-containing active sites. MFCs equipped with PGA/CB anodes (PGA/CB-MFCs) demonstrated superior power generation compared to GA/CB-MFCs and CB-MFCs (MFCs with GA/CB and CB anodes respectively), including a 23.0 % and 30.1 % reduction in start-up time, and an increase in maximum power density by 2.43 and 1.24 times respectively. The higher bioelectrochemical activity exhibited by the biofilm of PGA/CB anode and the promoted riboflavin secretion by PGA modification imply the enhanced EET efficiency. 16S rRNA high-throughput sequence analysis of the biofilms revealed successful enrichment of Geobacter on PGA/CB anodes. These findings not only validate the positive impact of the synergistic effects between GA and PDA in promoting EET and improving MFC performance but also provide valuable insights for electrode design in other bioelectrochemical systems.

A combination of microbial electrolysis cells and bioaugmentation can effectively treat synthetic wastewater containing polycyclic aromatic hydrocarbon

The anaerobic biodegradation of polycyclic aromatic hydrocarbons (PAHs) is challenging due to its toxic effect on the microbes. Microbial electrolysis cells (MECs), with their excellent characteristics of anodic and cathodic biofilms, can be a viable way to enhance the biodegradation of PAHs. This work assessed different cathode materials (carbon brush and nickel foam) combined with bioaugmentation on typical PAHs-naphthalene biodegradation and analyzed the inhibition amendment mechanism of microbial biofilms in MECs. Compared with the control, the degradation efficiency of naphthalene with the nickel foam cathode supplied with bioaugmentation dosage realized a maximum removal rate of 94.5 ± 3.2%. The highest daily recovered methane yield (227 ± 2 mL/gCOD) was also found in the nickel foam cathode supplied with bioaugmentation. Moreover, the microbial analysis demonstrated the significant switch of predominant PAH-degrading microorganisms from Pseudomonas in control to norank_f_Prolixibacteraceae in MECs. Furthermore, hydrogentrophic methanogenesis prevailed in MEC reactors, which is responsible for methane production. This study proved that MEC combined with bioaugmentation could effectively alleviate the inhibition of PAH, with the nickel foam cathode obtaining the fastest recovery rate in terms of methane yield.

Nano-hydroxyapatite/carbon nanotube: An excellent anode modifying material for improving the power output and diclofenac sodium removal of microbial fuel cells

Anode material and surface properties have a crucial impact on the performance of MFCs. Designing and fabricating various modified carbon-based anodes with functional materials is an effective strategy to improve anode performance in MFCs. Anode materials with excellent bioaffinity can promote bacterial attachment, growth, and extracellular electron transfer. In this study, positively charged nano hydroxyapatite (nHA) with remarkable biocompatibility combined with carbon nanotubes (CNTs) with unique structure and high conductivity were used as anode modifying material. The nHA/CNTs modified carbon brush (CB) exhibited improved bacteria adsorption capacity, electrochemical activity and reticular porous structure, thus providing abundant sites and biocompatible microenvironment for the attachment and growth of functional microbial and accelerating extracellular electron transfer. Consequently, the nHA/CNTs/CB-MFCs achieved the maximum power density of 4.50 ± 0.23 mW m-2, which was 1.93 times higher than that of the CB-MFCs. Furthermore, diclofenac sodium (DS), which is a widely used anti-inflammatory drug and is also a persistent toxic organic pollutant constituting a serious threat to public health, was used as the model organic pollutant. After 322 days of long-term operation, enhanced diclofenac sodium removal efficiency and simultaneous bioelectricity generation were realized in nHA/CNTs/CB-MFCs, benefiting from the mature biofilm and the diverse functional microorganisms revealed by microbial community analysis. The nHA/CNTs/CB anode with outstanding bioaffinity, electrochemical activity and porous structure presents great potential for the fabrication of high-performance anodes in MFCs.

Advancements on sustainable microbial fuel cells and their future prospects: A review

A microbial fuel cell (MFC) is a sustainable device that produces electricity. The main components of MFC are electrodes (anode & cathode) and separators. The MFC's performance is ascertained by measuring its power density. Its components and other parameters, such as cell design and configuration, operation parameters (pH, salinity, and temperature), substrate characteristics, and microbes present in the substrate, all influence its performance. MFC can be scaled up and commercialized using low-cost materials without affecting its performance. Hence the choice of materials plays a significant role. In the past, precious and non-precious metals were mostly used. These were replaced by a variety of low-cost carbonaceous and non-carbonaceous materials. Nano materials, activated compounds, composite materials, have also found their way as components of MFC materials. This review describes the recently reported modified electrodes (anode and cathode), their improvisation, their merits, pollutant removal efficiency, and associated power density.

Promoting the anode performance of microbial fuel cells with nano-molybdenum disulfide/carbon nanotubes composite catalyst

The design and manufacture of advanced anode materials with superior quality are significant for assembling high-performance microbial fuel cells (MFCs). The present study aims to investigate the synergistic effect of MoS₂/CNTs nanocomposite as a novel anode-modifying material of MFCs. XRD, XPS, SEM, TEM and electrochemical analyses were performed to confirm the nanocomposite, to understand the morphology and to study the electrochemical properties of the modified electrodes. The performance of the MoS₂/CNTs/carbon paper (CP)-MFCs was investigated and compared with that of MoS₂/CP-MFCs, CNTs/CP-MFCs and CP-MFCs. The densest biofilm was formed on MoS₂/CNTs-modified anode compared to MoS₂/CP, CNTs/CP and CP anode, and MFCs with MoS₂/CNTs-modified anodes achieved the maximum power density of 645 ± 32 mW m^-2, which is three times greater than MFCs with bare carbon paper anodes (213 ± 10 mW m^-2). These results demonstrate that the synthesized MoS₂/CNTs nanocomposite could be exploited as an efficient anode catalyst for improving the performance of MFCs.

Carbon-Based Composites as Anodes for Microbial Fuel Cells: Recent Advances and Challenges

Owing to the low price, chemical stability and good conductivity, carbon-based materials have been extensively applied as the anode in microbial fuel cells (MFCs). In this review, apart from the charge storage mechanism and anode requirements, the major work focuses on five categories of carbon-based anode materials (traditional carbon, porous carbon, nano-carbon, metal/carbon composite and polymer/carbon composite). The relationship is demonstrated in depth between the physicochemical properties of the anode surface/interface/bulk (porosity, surface area, hydrophilicity, partical size, charge, roughness, etc.) and the bioelectrochemical performances (electron transfer, electrolyte diffusion, capacitance, toxicity, start-up time, current, power density, voltage, etc.). An outlook for future work is also proposed.