Cathode Microbial Fuel Cells Research Articles

Degradation of refractory organics in dual-cathode electro-Fenton using air-cathode for H2O2 electrogeneration and microbial fuel cell cathode for Fe2+ regeneration

The electrogeneration of H2O2 and electro-regeneration of ferrous are conflicting matters in electro-Fenton system. In this research, the degradation of Rhodamine B, methyl orange (MO) and 4-chlorophenol (4-CP) was investigated using a novel dual-cathode microbial fuel cell (MFC) electro-Fenton (EF) hybrid system. An air-cathode of an EF system was used for H2O2 electrogeneration and a carbon felt cathode of a MFC was used to accelerate Fe2+ regeneration. Synergistic improvement of MFC power generation and the degradation of the above refractory organics through EF reaction was achieved. The EF air-cathode was fabricated by adopting activated carbon/graphite powder mixture and PVDF binder, which showed higher H2O2 generation but slower Fe3+ reduction rate than MFC carbon felt cathode. The Rhodamine B removal rate constant and mineralization current efficiency of the MFC coupled EF were 64% and 42% higher than that of uncoupled EF, respectively. The MFC-EF coupled system also exhibited significantly higher removal efficiency for MO and 4-CP than that of un-coupled EF system. Moreover, the power density of MFC was greatly enhanced by coupling EF due to higher Fe3+/Fe2+ redox potential than oxygen reduction.

High electricity generation achieved by depositing rGO@MnO2 composite catalysts on three-dimensional stainless steel fiber felt for preparing the energy-efficient air cathode in microbial fuel cells

Microbial fuel cells (MFCs) are a promising biotechnology that realizes the transformation of wastewater treatment from an energy consumption to an electricity generation process. However, the tedious process and the large resources consuming in preparing powder ORR catalysts are still non-negligible limiting factors for application. This study aims at proposing an energy-efficient method for preparing three-dimensional binder-free air cathode for MFCs: non-noble composite catalysts based on graphene and MnO2 are synthesized directly on stainless steel fiber felt (SSFF) by pre-fixing and electro-reducing graphene oxide on SSFF (rGO-SSFF), and then in-situ depositing MnO2 nanocatalysts on rGO-SSFF (rGO@MnO2-SSFF). The experimental results show that the ORR ability of rGO@MnO2-SSFF cathode is greater than that of Pt/C-CC cathode, even if the performance of rGO@MnO2 powder catalyst is slightly lower than that of the traditional Pt/C catalyst. The excellent performance is found to be due to the three-dimensional framework-pore structure of SSFF which helps the prepared cathode possess larger electrochemical active area (8415.18 m2 m−3) than Pt/C-CC cathode (7518.13 m2 m−3). The proposed method provides a new way to reduce the cost (labor, materials and energy) of air cathode while ensuring the high electricity output of MFCs.

Application of Air Cathode Microbial Fuel Cells for Energy Efficient Treatment of Dairy Wastewater

Microbial Fuel Cells (MFCs) offer a promising new solution for wastewater treatment due to their advantageous characteristics: lower energy demand and less excess sludge compared to the conventional activated sludge wastewater treatment technology. In this study, two systems of single chamber air cathode MFCs with a working volume of 14 L were investigated for the energy efficient treatment of dairy wastewater. Biomass-originated carbon cathode and noble-metal free cathode catalyst were applied to meet the demand for a lower investment cost. Influent chemical oxygen demand (COD) was in the range of 900 to 3830 mg L–1, while hydraulic retention time was ~ 2.4 days. Systems provided 156 mW m–3 and 170 mW m–3 maximum power densities and coulombic efficiencies of 11.5 % and 12.8 % in average. Organic removal efficiency of 71.1 ± 8.0 % was observed when influent COD was between 900 and 1500 mg L–1, however effluent quality and removal efficiency (67.9 ± 12.6 %) deteriorated as influent COD was increased (1500 – 3830 mg L–1). At high influent CODs (over 3000 mg L–1), an organic elimination rate of 0.82 ± 0.11 kg COD m–3 d–1 was calculated, that can be considered as the upper limit of organic removal in the systems. Based on the results, MFCs may offer a potential solution for small-scale dairy factories for the pretreatment of their effluent to meet the criteria for wastewater discharge to sewer systems. The modular MFC design also facilitates to tailor the system to actual capacity requirements.

Effect of carbon materials as cathode on wastewater treatment and bioelectricity generation in a double chambered microbial fuel cell

Microbial fuel cell (MFC) is a promising and sustainable technology that has high efficiency to produce renewable energy and treat wastewater simultaneously. The effect of carbon materials on the removal of synthetic wastewater in the anodic chamber and electricity generation were investigated using a double chambered MFC. In this study, a double chambered reactor made up of anodic and cathodic chambers separated by proton exchange membrane has been developed. Carbon plate and carbon felt were characterized using scanning electron microscopy. Results revealed that 1.20 times higher chemical oxygen demand removal of synthetic wastewater using carbon felt (50.90%) as compared with that of carbon plate (43.52%). The maximum voltage output produced by carbon felt (280.20 mV) was 20.70% higher than carbon plate (222.20 mV) as cathode in MFC. The surface morphology of carbon materials has significant effect on the oxygen reduction reaction reactivity at cathodic chamber.

Removal of Radioactive Ions in Low-Concentration Nuclear Industry Wastewater with Carbon-Felt Based Iron/Manganese/Zirconium Polycrystalline Catalytic Cathode in a Dual Microbial Fuel Cell

Removal of Radioactive Ions in Low-Concentration Nuclear Industry Wastewater with Carbon-Felt Based Iron/Manganese/Zirconium Polycrystalline Catalytic Cathode in a Dual Microbial Fuel Cell

Review on High-Performance Air Cathode Microbial Fuel Cell for Power Generation and COD Reduction

The world population is projected to increase by one billion for the next ten years from the year 2016. Unfortunately, global power plants still using non-renewable energy sources. Consumption of fossil fuels harms the environment, while nuclear energy could release a significant amount of radioactive material. Besides the energy issues, the growth in population contributes to the high production of wastewater. Every year, the wastewater treatment industry consumes a high input of energy for treatment purposes. These issues invigorate research interest in microbial fuel cell (MFC) technology that can generate green power electricity while breaking down the organic matter in the wastewater. One of the research advancement in MFC is the air-cathode MFC that is scaled-up friendly due to its simple structure, and ability to utilize the abundance of oxygen in the air as the membrane and scaling up arrangements. Therefore, this review aims to discuss the main positive findings contributing to the recent improvement of air-cathode MFC and the obstacles faced for upscaling.

Evaluation of a continuous flow microbial fuel cell for treating synthetic swine wastewater containing antibiotics

Microbial fuel cell (MFC) systems are promising technologies for wastewater treatment and renewable energy generation simultaneously. Performance of a double-chamber microbial fuel cell (MFC) to treat synthetic swine wastewater containing sulfonamide antibiotics (SMs) was evaluated in this study. The MFC was operated in continuous modes at different conditions. Results indicated that the current was successfully generated during the operation. The performance of MFC under the sequential anode-cathode operating mode is better than that under the single continuous running mode. Specifically, higher removal efficiency of chemical oxygen demand (>90%) was achieved under the sequential anode-cathode operating mode in comparison with that in the single continuous mode (>80%). Nutrients were also be removed in the MFC's cathode chamber with the maximum removal efficiency of 66.6 ± 1.4% for NH4+-N and 32.1 ± 2.8% for PO43−-P. Meanwhile, SMs were partly removed in the sequential anode-cathode operating with the value in a range of 49.4%–59.4% for sulfamethoxazole, 16.8%–19.5% for sulfamethazine and 14.0%–16.3% for sulfadiazine, respectively. SMs' inhibition to remove other pollutants in both electrodes of MFC was observed after SMs exposure, suggesting that SMs exert toxic effects on the microorganisms. A positive correlation was found between the higher NH4+-N concentration used in this study and the removal efficiency of SMs in the cathode chamber. In short, although the continuous flow MFC is feasible for treating swine wastewater containing antibiotics, its removal efficiency of antibiotics requires to be further improved.

Long-term operation of bio-catalyzed cathodes within continuous flow membrane-less microbial fuel cells

Microorganisms were observed to facilitate cathodic oxygen reduction and enhance cathode performance of microbial fuel cells (MFCs). However, the long-term activity and stability of bio-catalyzed cathode needs to be explored. This study evaluated the long-term performance of bio-catalyzed cathode and iron(II) phthalocyanine (FePc)-catalyzed cathode MFCs through effluent water quality, electricity production and electrochemical impedance spectroscopy (EIS) analysis under different scenarios, including conventional wastewater treatment and energy harvesting using a power management system (PMS). During the continuous operation, both systems demonstrated high chemical oxygen demand and ammonium removal, but bio-catalyzed cathode MFCs could achieve significantly better total nitrogen removal than FePc-catalyzed cathode MFCs. The FePc-coated cathode showed constant cathode potential during the entire operation period, but the biocathode showed varied but step-wise increased cathode potential to achieve more than 500 mV versus the standard hydrogen electrode, likely due to the gradual enrichment of biocathode biofilm. EIS analysis revealed that biocathode had higher ohmic resistance than bare carbon felt cathode but the microbial biofilm could largely decrease polarization resistance of cathode material. Microbial community analysis has shown the presence of nitrifying and denitrifying bacteria in the bio-catalyzed cathode biofilm. When connecting PMS, both bio-catalyzed cathode and FePc-catalyzed cathode MFCs successfully charged a capacitor, but the bio-catalyzed cathode MFC voltage significantly dropped to less than 100 mV after charging for 91 h, and gradually recovered when disconnecting PMS. This study has demonstrated the potential application of oxygen reduction bio-catalyzed cathode MFCs for continuous wastewater treatment and energy harvesting for long period of time.

Increasing bioelectricity generation in microbial fuel cells by a high-performance cellulose-based membrane electrode assembly

Economically harvesting energy from a microbial fuel cell (MFC), increasing its electrical power production, and developing its role as a practical energy supply, needs a low-cost and high-performance design of the MFC compartments. According to this strategy, a novel monolithic membrane electrode assembly (MEA) was fabricated and evaluated as an air–cathode in a single-chamber MFC (SCMFC). The MEA was made of bacterial cellulose (BC), conductive multi-walled carbon nanotubes (CNT), and nano-zycosil (NZ). BC, as a nano-celluloses with oxygen barrier property, can maintain anaerobic conditions for the anode compartment. Binder-less CNT coating on BC avoids costly binders such as poly-tetra fluoro ethylene (PTFE) and Nafion and decreases the MEA charge transfer resistance. NZ, as a very cheap modifier, not only prevents the anolyte leakage but also provides more MEA’s active sites for the oxygen reduction reaction (ORR). The electrochemical performance of the MEA was compared to a PTFE- based gas diffusion electrode (GDE) in the SCMFC. The MEA cell provided a pulse power density of 1790 mW/m2, roughly twice as high as the pulse power density of GDE (920 mW/m2). SCMFC’s internal resistance decreased from 1.84 KΩ (with GDE) to 0.8 KΩ (with MEA). Also, the cell’s columbic efficiency increased from 4.2% (with GDE) to11.7% (with MEA). Additionally, the capacitance of the MEA (65 mF) was much higher than the value for GDE (0.73 mF). Thus, the MEA compared to the GDE showed higher performance in the SCMFC for electricity generation and wastewater treatment at a lower cost.

Leaf-like carbon frameworks dotted with carbon nanotubes and cobalt nanoparticles as robust catalyst for oxygen reduction in microbial fuel cell

In this investigation, a double Zeolitic Imidazolate Frameworks (ZIF) precursor is used to synthesize a leaf-like cobalt/nitrogen co-doped porous carbon embedded with carbon nanotubes (Co–N–PC@CNTs), as a catalyst to modify an activated carbon air cathode microbial fuel cell (MFC). The unique leaf structure of carbon frameworks, which is rich in carbon nanotubes and cobalt nanoparticles on the surface, is confirmed to accelerate the oxygen reduction reaction (ORR) through a four-electron pathway similar to Pt/C. The time-current test reveals the remarkable stability of indicated by the retain of around 92% current after 12 h. The electrochemical reactions with Co–N–PC@CNTs are far superior to the control group. What's more, the best improved MFC exhibits outstanding exchange current density (27.83 × 10−4 A cm−2), and the optimized power density of MFC reaches 2479 ± 70 mW m−2, which is 247.2% higher than that of the control group (714 ± 59 mW m−2). In addition, Co–N–PC@CNTs modified activated carbon cathode MFC has an excellent chemical oxygen demand (COD) removal rate of 86.52%, which is significantly better than the control group (50.51%). Therefore, Co–N–PC@CNTs is considered to be a promising MFC cathode catalyst.

Nitrogen oxide gas purification using carbon in water as reducing reagent with the aid of microbial fuel cell

Microbial Fuel Cell (MFC) can degrade the organic matter (OM) in wastewater at the anode and transfer electrons to the cathode. In this work, the harmful NOX gas was used as electron acceptor in MFC and converted to harmless N2. The OM in water was indirectly used as a zero-cost reducing agent for NOx removal. More than 80% of NOX was removed continuously by MFC at room temperature. The NOX was directly reduced to N2 at MFC cathode and the cathode activity played a key role on enhancing the NOX removal. The NOX removal efficiency by the cathode of high potential was 1.37 times that by the cathode of low potential. When O2 coexisting with NO as the electron acceptor, not only the NOX removal but also the power output of MFC was improved greatly. The presence of NOX did not decrease the power generation of MFC under the same O2 concentration. The MFCs showed good stability for NOX treatment and power output. Moreover, the possible pathways and advantages of NOX removal by MFC were discussed in detail. These results indicated that the MFC system has the potential to treat wastewater, purify flue gas and recover energy simultaneously.

Impregnated thermoset pre-pressurized carbon composite electrodes in microbial fuel cell: Compositional functionalities influence on ORR with reference to graphite

Advancement in developing specific compositional functionalities of electrodes that are energy-recovery efficient, cost-effective, durable and catalytically active is particularly challenging for microbial fuel cell (MFC) operation due to its bio-compatibility requirement. Compositional characteristics of the electrodes influence the electron charge-discharge rates, oxidation-reduction reaction and biofilm formation. In this study, compact carbon-carbon composite electrode (C/C composite), fabricated by high pressure hot-pressing method followed by densified low-pressure impregnation thermosetting carbonization, was evaluated as both anode and cathode in dual-chambered MFC with varied combinations with graphite electrode. Fed-batch experiments were operated with four combinations of electrode using 3 g/l glucose in designed synthetic wastewater as anolyte and oxygenated water as catholyte. C/C composite as cathode and graphite as anode (MFC-GC) depicted comparatively higher power density (0.37 W/m2) and current (2 A/m2) than the other configurations. Improved oxidation–reduction rate (ORR) kinetics enabled higher bioelectrogenic activity in MFC-GC with respect to the elemental and surface functionalities of C/C composite electrode. Bioelectrochemical analysis showed increased charge-transfer capacitance and electron flux while lowering the system losses in MFC-GC. The capability of C/C composite electrodes as cathode due to presence of higher oxygen functionalities and surface properties increased the oxidation-reduction rate kinetics towards higher energy output during MFC operation.

Boosting the cathode function toward the oxygen reduction reaction in microbial fuel cell using nanostructured surface modification

AbstractProduction of bioelectricity via microbial fuel cells (MFCs) may become an important source of energy in the near future due to the possibility of extracting electric current from a wide range of organic wastes. In this study, several nanostructures, such as platinum (Pt)‐reduced graphene oxide nanocomposite, graphene nanosheets, MnO2, and MnO2/RGO, were synthesized, characterized, and investigated as cathode catalysts for oxygen reduction reaction. The prepared catalysts were tested in a single‐chamber microbial fuel cell with anaerobic bacterial mixed culture. Power density produced from MFC closed circuit operation using the nanoengineered catalysts were about 68 times more than those obtained using the classical graphite electrodes. Moreover, there was a slight reduction of 5.8% in power density (from 170 to 160 mW/m2) when Pt nanoparticles were loaded on the RGO nanosheets compared to Pt/C cathode. By replacing the precious Pt catalyst with other nanomaterials, a significant reduction in power density was observed. For RGO‐based cathode, the MFC performance decreased by 31.1% (from 170 to 117 mW/m2) and the percent of reduction reached 48.5% (from 170 to 88 mW/m2) for MnO2‐based cathode MFC. However, in RGO/MnO2 nanocomposite cathode MFC, the percent of reduction in power density was 26.4% (from 170 to 125 mW/m2). It can be concluded that RGO nanosheets loaded with Pt nanoparticles is a starting point for finding an alternative economic and effective cathode.

Enhanced bioelectrochemical performance caused by porous metal-organic framework MIL-53(Fe) as the catalyst in microbial fuel cells

To enhance the oxygen reduction reaction (ORR) activity and power generation capacity of a microbial fuel cell (MFC), MIL-53(Fe) (Fe-based Materials of Institute Lavoisier) as the electrochemical catalyst was synthesized using the hydrothermal method. The catalytic structure and morphology of all materials were comprehensively characterized by Fourier Transform infrared spectrometer (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that there were many nanopores on MIL-53(Fe), which improved the electrocatalytic activity. The MIL-53(Fe)-modified air cathode MFC had a voltage output of approximately 0.37 V and maintained that output for one week. The maximum power density was 397 ± 6.3 mW/m2. MIL-53(Fe) was an excellent electrochemical catalyst, significantly enhancing the catalytic oxygen reduction ability and promoting the power output of the MFC. This study provides a method to apply MIL-53(Fe) materials in microbial fuel cells.

Biomass-derived N-doped porous activated carbon as a high-performance and cost-effective pH-universal oxygen reduction catalyst in fuel cell

Nitrogen (N) doped porous activated carbons (TGC-T) derived from tofu gel are prepared through a facile, economic and eco-friendly method. The as-prepared TGC-900 possesses high specific surface area (651.78 m2 g−1) and homogeneous doping N (Content of N: 5.52 at.%). Reasonably, TGC-900 exhibits excellent oxygen reduction reaction (ORR) activity, stability and methanol resistance in neutral, alkaline and acidic medium. Moreover, TGC-900 also shows outstanding ORR performance in the application of microbial fuel cell (MFC) with the highest output voltage (544 ± 6 mV) and maximum power density (977 ± 32 mW m−2). Inspiringly, four single-chamber air cathode MFCs (AC-MFCs) in series can drive a light-emitting diode (LED) to work is firstly reported which further provides a more intuitively method to evaluate the performance of generating electricity for MFCs. Thus, the high performance and cost-effective ORR catalyst TGC-900 is expected to apply in the field of fuel cells.

Impact of cathodic electron acceptor on microbial fuel cell internal resistance

Ferricyanide is often used in microbial fuel cells (MFCs) to avoid oxygen intrusion that occurs with air cathodes. However, MFC internal resistances using ferricyanide can be larger than those with air cathodes even though ferricyanide results in higher power densities. Using a graphite fiber brush cathode and a ferricyanide catholyte (FC-B) the internal resistance was 62 ± 4 mΩ m2, with 84 ± 8 mΩ m2 obtained using ferricyanide and a flat carbon paper cathode (FC-F) and only 51 ± 1 mΩ m2 using a 70% porosity air cathode (A-70). The FC-B MFCs produced the highest maximum power density of all configurations examined: 2.46 ± 0.26 W/m2, compared to 1.33 ± 0.14 W/m2 for the A-70 MFCs. The electrode potential slope (EPS) analysis method showed that electrode resistances were similar for ferricyanide and air–cathode MFCs, and that higher power was due to the larger experimental working potential (500 ± 12 mV) of ferricyanide compared to the air cathode (233 ± 5 mV).

Influence of Humidity on Performance of Single Chamber Air-Cathode Microbial Fuel Cells with Different Separators

The maximum performance of microbial fuel cells (MFCs) is significantly affected by the reduction reactions in the cathode, but their optimum condition is not fully understood yet. The air-cathode MFC operations with different separators (Nafion 117 and polypropylene (PP80) were evaluated at various relative humidity (RH) at the cathode chamber. Air cathode MFCs with a Nafion 117 separator at RH of 90 ± 2% produced the highest cell voltage of 0.35 V (600 Ω) and power density of 116 mW/m2. With a PP80 separator, the maximum power generation of 381 mW/m2 was obtained at a relatively lower RH of 30 ± 2%. The cyclic voltammogram and Tafel analysis indicated that the best performance of cathodic oxygen reduction reactions could be observed at 90% RH for Nafion and 50% RH for the PP80 separator. Additionally, the RH conditions also affected the anodic reactions and oxygen mass transfer rates to the anode chamber through the cathode and separators. This study suggests that the optimum RH condition at the cathode is important in order to obtain a high performance of MFC operations and needs to be controlled at different optimum levels depending on the characteristics of the separators.

Bioanode-Assisted Removal of Hg 2+ at the Cathode of Microbial Fuel Cells

Abstract The removal of heavy metals from contaminated waters is highly desirable to circumvent their toxic effects on the ecosystem and human health. In this study, we report on the bioanode-assis...

Electricity Effectively Utilization by Integrating Microbial Fuel Cells with Microbial Immobilization Technology for Denitrification

We report a novel strategy of integrating microbial fuel cell (MFC) with microbial immobilization technology (MIT) in a sequencing batch reactor (SBR) to test the performance of nitrate removal for the first time. Results showed that MFC could enhance nitrate removal in the novel integrated system, especially for wastewater with low carbon-to-nitrogen ratios, and the nitrate removal efficiency reached 91.35% in the lab-scale integrated system, including 12.25% nitrate consumption by MFC in one typical cycle. The anode of MFC recovered energy in the form of electricity, floating cathode of MFC prevented the loss of immobilized denitrifying bacteria particles and degraded a portion of nitrate, and the maximum voltage production of MFC was 0.246 V. The novel integrated system in this paper showed excellent nitrate removal performance and it will be a highly potential novel setup for efficient nitrate removal of wastewater treatment.

Microbial Fuel Cell for Electrical Power Generation from Waste Water

In the last decades, the microbial fuel cell (MFC) has increased great opportunity as an alternative energy source through electrochemical process for producing bio-energy. MFC has been involved in anode and cathode for electric energy generation from organic ingredients such as bacteria in waste water treatment. In this review, we discussed the different types of MFC (anode and cathode) materials with various integrations. In addition, it includes the gainful, biocompatible and exceedingly constant electrode materials with enhanced microbial fuel cell performance. Following this review, expansion in membrane materials such as hydrocarbon polymer, perfluorinated polymer, organic-organic hybrid polymer, ceramics, organic-inorganic hybrid composite, and biopolymer membranes are clarified in detail. In this paper, also highlighted the application of MFC technology and the methods used in the MFC in electricity production.