Biocathode Microbial Fuel Cells Research Articles

Granular activated carbon assisted biocathode for effective electrotrophic denitrification in microbial fuel cells

Granular activated carbon (GAC) has been widely used at the anode of a microbial fuel cell (MFC) to enhance anode performance due to its outstanding capacitance property. To the best of our knowledge, there haven't been any studies on GAC in the cathode for biofilm development and nitrate reduction in MFC. In this study, by adding GAC to biocathode, we investigated the impact of different GAC amounts and stirring speeds on power generation and nitrate reduction rate in MFC. The denitrification rate was found to be nearly two-times higher in MFCs with GAC (0.046 ± 0.0016 kg m−3 d−1) compared to that deprived of GAC (0.024 ± 0.0012 kg m−3 d−1). The electrotrophic denitrification has produced a maximum power density of 37.6 ± 4.8 mW m−2, which was further increased to 79.2 ± 7.4 mW m−2 with the amount of GAC in the biocathode. A comparative study performed with chemical catalyst (Pt carbon with air sparging) cathode and GAC biocathode showed that power densities produced with GAC biocathode were close to that with Pt cathode. Cyclic voltammetry analysis conducted at 10 mV s−1 between −0.9 V and +0.3 V (vs. Ag/AgCl) showed consistent reduction peaks at −0.6V (Ag/AgCl) confirming the reduction reaction in the biocathode. This demonstrates that the GAC biocathode used in this research is effective at producing power density and denitrification in MFC. Our belief that the nitrate reduction was caused by the GAC biocathode in MFC was further strengthened when SEM analysis showing bacterial aggregation and biofilm formation on the surface of GAC. The GAC biocathode system described in this research may be an excellent substitute for MFC's dual functions of current generation and nitrate reduction.

Light-induced aquaculture wastewater valorization, nutrient recovery, and microalgae biomass production in a biocathode-assisted microbial fuel cell

The present study investigates how well the light quality (white, blue, and red light) affects the growth and biochemical profiling of freshwater microalga Scenedesmus obliquus grown on aquaculture wastewater as a nutrient source in a biocathode microbial fuel cell (MFC). The findings show that the electrochemical behaviour of the MFCs varied with the use of different wavelengths, suggesting that light quality and photosynthetic evolved oxygen increased MFC voltage. Sc. obliquus showed the highest percentage of nutrient removal for blue light-operated biocathode MFC. Blue light maximized biomass production with a cell density of 1.54 ± 0.065 OD680 and Chl-a concentration of 12 ± 1.2 mgL−1 during 6-day cultivation. Valorization of aquaculture using MFC proved successful in nutrient recovery and microalgae biomass production, primarily upon exposure to blue light.

Electroactive microorganisms synthesizing iron sulfide nanoparticles for enhanced hexavalent chromium removal in microbial fuel cells

Microbial fuel cells (MFCs) have been considered a promising technology for Cr6+ removal, but they are limited by Cr6+-reducing biocathodes with low extracellular electron transfer (EET) and poor microbial activity. In this study, three kinds of nano-FeS hybridized electrode biofilms, obtained through synchronous biosynthesis (Sy-FeS), sequential biosynthesis (Se-FeS) and cathode biosynthesis (Ca-FeS), were applied as biocathodes for Cr6+ removal in MFCs. The Ca-FeS biocathode exhibited the best performance due to the superior properties of biogenic nano-FeS (e.g., more synthetic amount, smaller particle size, better dispersion). The MFC with the Ca-FeS biocathode achieved the highest power density (42.08 ± 1.42 mW/m2) and Cr6+ removal efficiency (99.18 ± 0.1 %), which were 1.42 and 2.08 times as high as those of the MFC with the normal biocathode, respectively. The synergistic effects of nano-FeS and microorganisms enhanced the bioelectrochemical reduction of Cr6+, first realizing deep reduction of Cr6+ to Cr0 in biocathode MFCs. This significantly alleviated the cathode passivation caused by Cr3+ deposition. In addition, the hybridized nano-FeS as “armor” layers protected the microbes from toxic attack by Cr6+, improving the biofilm physiological activity and extracellular polymeric substances (EPS) secretion. The hybridized nano-FeS as “electron bridges” facilitated the microbial community to form a balanced, stable and syntrophic ecological structure. This study proposes a novel strategy through the cathode in-situ biosynthesis of nanomaterials to fabricate hybridized electrode biofilms with enhanced EET and microbial activity for toxic pollutant treatment in bioelectrochemical systems.

Denitrification in perspective of carbon neutralization: CO2 emission reduction and electricity generation by Fe-anode and bio-cathode MFC

In order to solve the problem of insufficient carbon source for denitrification in sewage treatment plants (STPs), iron-dependent autotrophic denitrification was investigated. Combining the iron-dependent autotrophic denitrification and the microbial fuel cell (MFC) would not only be economical to remove nitrate in wastewater but also be environmentally friendly. With iron as anode and denitrification biofilm on the cathode, the Fe-MFC is operated continuously for 42 days (in total 6 cycles). With removal efficiency of 92% and volumetric removal rate of 0.0055 kg-N·m−3·d−1, nitrate is successfully removed with no CO2 emission. The output voltage of the MFC maintained at 540 mV for 80 h, and then it decreases linearly to below 15 mV with the consumption of substrate (nitrate) under sequencing batch operation. Along with the consumption/passivation of iron-anode and the adaption of microbes to the new environment, the electric power and the Volt-ampere charge (q*) of bio-cathode dropped from cycle 1 to cycle 6 by 39% and 44% respectively. The microbial community analysis showed that the dominant genus in the biofilm was Thauera which could use electrode electrons as electron donor directly. With Fe-MFC both CO2 emission reduction and electricity generation came true for denitrification. The Fe-MFC technology is feasible to treat nitrogen pollution in low C/N wastewater. It also provides new thought for denitrification under carbon neutralization policy.

Effect of Nitrate Concentration on the Coupling Process of Electricity Generation and Nitrate Removal in Biocathode Microbial Fuel Cells

The effect of nitrate (NO3−-N) concentration in catholyte on electricity generation and pollutant removal was investigated in biocathode microbial fuel cells (BMFCs). Results indicated that the NO3−-N removal rate and output voltage could be promoted with increasing NO3−-N concentrations, but both of them would be inhibited when the NO3−-N concentrations was more than 100.0 mg/L. The maximum NO3−-N removal rate and the maximum output voltage was 0.833 mg/(L/h) and 406 mV, respectively, when the initial NO3−-N concentration was 100.0 mg/L. Based on the Han–Levenspiel model, the kinetics of NO3−-N removal and output voltage were established in which the maximum NO3−-N removal rate was 1.06 mg/(L/h), and the maximum output voltage was 478 mV. Moreover, NO3−-N concentrations had a great impact on the coupling of electricity generation and NO3−-N removal, which indicated that electricity generation was closely related to the NO3−-N removal. In addition, it was found that the community structure in the cathode biofilm by high-throughput sequencing changed at different NO3−-N biofilm as measured by the main functional microbial genus responsible for removing NO3−-N, which remained as denitrifying Proteobacteria.

Bioelectricity generation using long-term operated biocathode: RFLP based microbial diversity analysis

In the present work, power generation and substrate removal efficiencies of long-term operated microbial fuel cells, containing abiotic cathodes and biocathodes, were evaluated for 220 days. Among the two microbial fuel cell (MFC) types, the one containing biocathode showed higher power density (54 mW/m2), current density (122 mA/m2) coulombic efficiency (33%), and substrate removal efficiency (94%) than the abiotic cathode containing MFC. Voltammetric analysis also witnessed higher and sustainable electron discharge for the MFC with biocathode, when compared with the abiotic cathode MFC. Over the tested period, both MFC have shown a cell voltage drop, after 150 and 165, days, for the MFC with biocathode and abiotic cathodes, respectively. Polymerase chain reaction (PCR) based restriction fragment length polymorphism (RFLP) analysis identified 281 clones. Bacteria belonging to Acinetobacter, Acidovorax, Pseudomonas and Burkholderia were observed in the abiotic cathode MFC. Bacteria belonging to Geobacter, Cupriavidus and Acidobacteria were observed in the biocathode MFC. Almost similar types of archaea (Methanosarcinales, Methanolinea, Nitrososphaera and Methanomicrobiales) were observed in both MFCs.

Removal of Cd and Ni with enhanced energy generation using biocathode microbial fuel cell: Insights from molecular characterization of biofilm communities

The present study explores the potential of using biocathode for enhanced energy recovery from wastewater and removal of toxic metals Cd and Ni from aqueous solutions in a double chamber Microbial Fuel Cell (MFC) overcoming the challenge of their less favoured removal owing to low redox potential. Wetland sediment was used as inoculum both in anode and cathode chambers. Power density generated by biocathode MFC from diluted distillery wastewater was 722 mW/m3, which was 10 times that produced by the abiotic MFC. At 10 mgL−1 concentration, 92% Ni and 87% Cd were removed, while at 25 mgL−1 concentration, removal increased by 70% when biocathode was used. Microbial characterization of biofilms, using 16S metagenomic sequencing revealed that diversity of microbial communities developed on the anode and cathode biofilms were quite different though inoculum source was the same. Metal tolerant γ-proteobacteria, exopolysaccharide producing and metal chelating genera like Ochrobactrum and Halomonas were abundant in cathodic biofilm that seem involved in Ni and Cd removal. Anodic biofilm was mostly dominated by the orders Clostridiales and Burkholderiales (class β-proteobacteria), and the fermentor genus Achromobacter was dominant. The novel approach of using biocathode in the MFC, thus significantly improved the removal of Ni and Cd from single as well as mixed metal solutions along with remarkable increase in energy recovery without any use of expensive catalysts, and characterisation of the biofilm at anode and cathode indicated how the microbial communities originating from same inoculum differed in their composition perform different roles of electricity production and metal removal in the MFC.

Energy recovery and carbon/nitrogen removal from sewage and contaminated groundwater in a coupled hydrolytic-acidogenic sequencing batch reactor and denitrifying biocathode microbial fuel cell

Developing cost-effective technology for treatment of sewage and nitrogen-containing groundwater is one of the crucial challenges of global water industries. Microbial fuel cells (MFCs) oxidize organics from sewage by exoelectrogens on anode to produce electricity while denitrifiers on cathode utilize the generated electricity to reduce nitrogen from contaminated groundwater. As the exoelectrogens are incapable of oxidizing insoluble, polymeric, and complex organics, a novel integration of an anaerobic sequencing batch reactor (ASBR) prior to the MFC simultaneously achieve hydrolytic-acidogenic conversion of complex organics, boost power recovery, and remove Carbon/Nitrogen (C/N) from the sewage and groundwater. The results obtained revealed increases in the fractions of soluble organics and volatile fatty acids in pretreated sewage by 52 ± 19% and 120 ± 40%, respectively. The optimum power and current generation with the pretreated sewage were 7.1 W m−3 and 45.88 A m−3, respectively, corresponding to 8% and 10% improvements compared to untreated sewage. Moreover, the integration of the ASBR with the biocathode MFC led to 217% higher carbon and 136% higher nitrogen removal efficiencies compared to the similar system without ASBR. The outcomes of the present study represent the promising prospects of using ASBR pretreatment and successive utilization of solubilized organics in denitrifying biocathode MFCs for simultaneous energy recovery and C/N removal from both sewage and nitrate nitrogen-contaminated groundwater.

Review of high-performance biocathode using stainless steel and carbon-based materials in Microbial Fuel Cell for electricity and water treatment

Biocathode application in Microbial Fuel Cell (MFC) is a promising alternative for sustainable energy production. This recognition is due to its low construction and operation costs as well as the utilization of microbial metabolism in assisting power generation. One of the most crucial factors contributes to the performance of a biocathode MFC is the characteristics and configuration of the biocathode material itself. Hence it requires improvement for a better understanding towards its bioelectrochemical mechanisms as well as improving the MFC performance. However, reports on improving biocathode through support material selection and performance optimization in MFCs are still lacking. Based on previous reports, studies have shown that carbon-based material and stainless steel are possible biocathode materials for high power MFC performance. This review focuses on comparing these potential biocathode materials, regarding the commonly applied biocathode MFC designs and optimization. This review also compares the performance of biocathode materials in MFC based on the bioelectricity production and wastewater treatment. Further studies and understanding can provide a useful basis in fabricating biocathode designs and configurations to produce better sustainable bioelectricity in MFCs.

A Facultative Electroactive Chromium(VI)-Reducing Bacterium Aerobically Isolated From a Biocathode Microbial Fuel Cell.

A facultative electroactive bacterium, designated strain H, was aerobically isolated from the biocathode of a hexavalent chromium (Cr(VI))-reducing microbial fuel cell (MFC). Strain H is Gram-positive and rod shaped (1–3 μm length). 16S rRNA gene analysis suggested that this strain (accession number MH782060) belongs to the genus Bacillus and shows maximum similarity to Bacillus cereus whose electrochemical activity has never previously been reported. Moreover, this strain showed efficient Cr(VI)-reducing ability in both heterotrophic (aerobic LB broth) and autotrophic (anaerobic MFC cathode) environments. Cr(VI) removal reached 50.6 ± 1.8% after 20 h in LB broth supplemented with Cr(VI) (40 mg/L). The strain H biocathode significantly improved the performance of the Cr(VI)-reducing MFC, achieving a maximum power density of 31.80 ± 1.06 mW/m2 and Cr(VI) removal rate of 2.56 ± 0.10 mg/L–h, which were 1.26 and 1.75 times higher than those of the MFC with the sterile control cathode, respectively. This study offers a novel Gram-positive Bacillus sp. strain for Cr(VI) removal in MFCs, and shows a facile aerobic isolation method could be used to screen facultative electroactive bacteria.

Simultaneous nutrient and carbon removal and electricity generation in self-buffered biocathode microbial fuel cell for high-salinity mustard tuber wastewater treatment

Mustard tuber wastewater (MTWW) was used as both anolyte and catholyte in biocathode microbial fuel cell (BMFC). The results showed simultaneous nutrient and carbon removal and electricity generation were realized in BMFC. Excellent Chemical Oxygen Demand (COD) removal occurred in both anode (>90%) and cathode (>91%). Concerning nutrient removal, it was mainly removed in cathode. The maximum total phosphorus (TP) removal could reach 80.8 ± 1.0% by biological action. Simultaneous nitrification and denitrification (SND) was realized in cathode. The bacteria involved in nitrification were Nitrosomonas and SM1A02. Oceanimonas and Saprospiraceae_uncultured (anaerobic denitrifier), Thauera, Stenotrophomonas, Flavobacterium and Marinobacter (aerobic denitrifier), and Thioalkalispira (autotrophic denitrifier) were responsible for denitrification. Considering slight variation of anode and cathode pH, it could be concluded that MTWW was adequately self-buffered when used as electrolyte. Furthermore, electricity generation decreased with cathodic dissolved oxygen (DO) declining. These findings provide a novel method for MTWW resourceful treatment.

Treatment of Simulated Wastewater by Bio-Cathode Microbial Fuel Cells at different C/N Ratio

The study combined the microbial fuel cells (MFC) technology with the carbon and nitrogen removal technology of sewage based on the principle of MFC, constructing and running a bio-cathode microbial fuel cells (BCMFC) which could remove the carbon and nitrogen of sewage and generate electricity at the same time. The results indicated that the BCMFC was able to deal with low C/N ratio and high ammonia concentration wastewater on the condition of continuous flow. When the BCMFC was operated at the C/N ratio of 4, 7, 10 and 13, the lower C/N ratio was, the better performance was. When the C/N ratio was 4, the BCMFC reached the maximum power density of 786mW/m3, the highest denitrification rate of 50.1 mg/(L.d) and removing of 1gN, consuming 6.99 g COD.

Optimization of sensing performance in an integrated dual sensors system combining microbial fuel cells and upflow anaerobic sludge bed reactor

Two bio-cathode microbial fuel cells (MFCs) with Upflow anaerobic sludge blanket (UASB) are integrated to construct a UASB-MFC dual sensors system, developed to solve the problems of low accuracy and less information about the single sensor system. The bio-cathode MFC is developed as the biosensor for UASB operation performance and online monitoring. Owing to the biosorption of anaerobic microbes, the MFC in the suspended layer is more suitable for effluent chemical oxygen demand (COD) real-time monitoring, and the MFC in the sludge layer is more suitable for total volatile fatty acid (TVFA) real-time monitoring. Electrochemical analysis discovers that the lower electron transfer resistance determines the higher sensitivity of MFC in the suspended layer. The difference in species abundance indicates that TVFA has a stronger inhibitory effect on MFC in the sludge layer. The novel UASB-MFC dual sensors system shows promising potential for COD and TVFA simultaneous online monitoring, which can enhance the reliability of anaerobic reaction.

Enhancing Electricity Generation Using a Laccase-Based Microbial Fuel Cell with Yeast Galactomyces reessii on the Cathode

The fungi associated with termites secrete enzymes such as laccase (multi-copper oxidase) that can degrade extracellular wood matrix. Laccase uses molecular oxygen as an electron acceptor to catalyze the degradation of organic compounds. Owing to its ability to transfer electrons from the cathodic electrode to molecular oxygen, laccase has the potential to be a biocatalyst on the surface of the cathodic electrode of a microbial fuel cell (MFC). In this study, a two-chamber MFC using the laccase-producing fungus Galactomyces reessii was investigated. The fungus cultured on coconut coir was placed in the cathode chamber, while an anaerobic microbial community was maintained in the anode chamber fed by industrial rubber wastewater and supplemented by sulfate and a pH buffer. The laccase-based biocathode MFC (lbMFC) produced the maximum open circuit voltage of 250 mV, output voltage of 145 mV (with a 1,000 Ω resistor), power density of 59 mW/m2, and current density of 278 mA/m2, and a 70% increase in half-cell potential. This study demonstrated the capability of laccase-producing yeast Galactomyces reessii as a biocatalyst on the cathode of the two-chamber lbMFC.

Assessment of recirculation batch mode operation in bufferless Bio-cathode microbial Fuel Cells (MFCs)

Biocathode microbial fuel cells are cost-effective and environmentally sustainable bio-electrochemical devices. However, the usage of buffer solution will significantly reduce the feasibility of the MFCs (Microbial Fuel Cells) for practical applications in the future. Therefore, in this study the function of PBS (Phosphate Buffer Solution) was substituted by application of recirculation flow mode to enhance the proton transfer. An innovative and novel endeavor of inserting a honey comb structure into an MFC for uniform influent flow was also performed. pH and power performance were investigated in aerobic biocathode MFCs at recirculation flow rates of 0 ml/min, 4 ml/min, 40 ml/min, and 240 ml/min. The results showed that higher recirculation flow rates maintained a steady pH after 1 h of MFC operation and efficiently reduced the time to achieve the favorable pH environment (7.0–7.55) for the growth of electrochemically active bacteria (EAB). Furthermore, the highest power density of 5.71 mW/m2 and lowest charge transfer resistance of 267.7 Ω were obtained at the flow rate of 40 ml/min. But, extremely high flow rate of 240 ml/min was found to be detrimental to the biocathode MFC and reduced the power density and charge transfer resistance. Therefore, these findings would provide useful and progressive insights for pilot and industrial scale studies with bufferless biocathode MFCs in the future.

Electrophoretic deposition of carbon nanotube on reticulated vitreous carbon for hexavalent chromium removal in a biocathode microbial fuel cell

For Cr(VI)-removal microbial fuel cell (MFC), a more efficient biocathode in MFCs is required to improve the Cr(VI) removal and electricity generation. RVC-CNT electrode was prepared through the electrophoretic deposition of carbon nanotube (CNT) on reticulated vitreous carbon (RVC). The power density of MFC with an RVC-CNT electrode increased to 132.1 ± 2.8 mW m−2, and 80.9% removal of Cr(VI) was achieved within 48 h; compared to only 44.5% removal of Cr(VI) in unmodified RVC. Cyclic voltammetry, energy-dispersive spectrometry and X-ray photoelectron spectrometry showed that the RVC-CNT electrode enhanced the electrical conductivity and the electron transfer rate; and provided more reaction sites for Cr(VI) reduction. This approach provides process simplicity and a thickness control method for fabricating three-dimensional biocathodes to improve the performance of MFCs for Cr(VI) removal.

Enhanced electricity generation for biocathode microbial fuel cell by in situ microbial-induced reduction of graphene oxide and polarity reversion

A simple effective and environmentally friendly pathway to form graphene modified biocathode was induced by polarity reversion of graphene modified bioanode, which was made by in situ microbial-induced reduction of graphene oxide (GO). Graphene assembled by microbes showed that D/G intensity increased from 0.84 to 0.91 and C/O atomic ratio added from 2.13 to 4.45, indicating GO was reduced largely. The graphene modified biocathode exhibited crumples that grown on the lamellar and glossy surface and was capable of improving catalytic reduction of oxygen. Microbial fuel cell (MFC) fabricated with graphene modified biocathode obtained 1.22 times in maximum power density, 0.21 times in interfacial charge transfer resistance, and recorded an obvious redox peaks at −0.50 V (vs. SCE) than control biocathode MFC. Geobacter, Clostridium, Pseudomonas, Geothrix and Hydrogenophaga belonged to exoelectrogens occupied 17.53% in graphene modified biocathode, 2.07% in control biocathode in genus level. This study provided a new insight into the feasibility to make microbes self-assembled graphene to improve electrochemical performance of biocathode MFC.

Cathodic Cr(VI) reduction by electrochemically active bacteria sensed by fluorescent probe

Biocathode microbial fuel cells (MFCs) have been shown to be useful in reductively changing Cr(VI) into Cr(III)-related precipitates on the surface of electrochemically active bacteria (EAB), but the occurrence of intracellular Cr(VI) reduction in the EAB are still unclear. Based on the four EAB isolated from Cr(VI)-reduced biocathode MFCs and tentatively assigned to Stenotrophomonas sp. YS1, Stenotrophomonas maltophilia YS2, Serratia marcescens YS3 and Achromobacter xylosoxidans YS8, a naphthalimide-rhodamine based Cr(III) fluorescent probe was used for the first time to sense the intracellular Cr(III) ions, inevitably and transiently formed from Cr(VI) reduction in these EAB. More Cr(VI) was reduced in the MFC biocathodes, resulting in intracellular accumulation of total chromium of 45.1±1.3–60.5±1.4% with a composite of Cr(III) ions (23.7±2.6–27.3±1.1%) and other forms of chromium-complex (18.7±2.5–32.2±0.8%). In the open circuit controls, intracellular total chromium only ranged 10.2±1.5–11.7±0.8% (Cr(III) ions: 8.2±0.6–9.5±0.9%; other forms: 0.2±0.6–0.3±0.9%). This study illustrates that cathode directed more intracellular Cr(VI) reduction in the EAB and gives an alternative approach for developing imaging and functionally sensing Cr(III) ions in the MFC biocathodes.

Accumulation of intermediate denitrifying compounds inhibiting biological denitrification on cathode in Microbial Fuel Cell.

BackgroundBio-cathode denitrifying microbial fuel cell (MFC) is a promising bio-electrochemical system (BES) where both the reactions of anodic oxidation and cathodic reduction are catalyzed by microorganisms. In this nitrogen removal process, a complete biological denitrification from nitrate (NO3-) to molecular nitrogen (N2) was achieved by four reduction steps, forming nitrite (NO2−), nitric oxide (NO) and nitrous oxide (N2O) as intermediate compounds. These enzymatic catalysis reductions are often slowed down on cathode electrode at the higher cathodic nitrate loading. This study investigated the cause for inhibition of the biological denitrification in a three-chambered MFC where the middle chamber acted as denitrifying bio-cathode and the two chambers at the side acted as bio-anode. Carbon fiber brushes were used as electrodes and nafion membranes were used as separator between the chambers.ResultsThe maximum power obtained was 14.63 W m−3 net cathodic compartment (NCC) (Rext =11.5Ω) at an optimum nitrate loading of 0.15 kg NO3−-N m−3 NCC d−1. The accumulation of one of the intermediate denitrifying compound, e.g., NO2− adversely affected biological denitrification rate on cathode. According to chemical kinetics, the accumulated NO2− will form free nitrous acid (FNA, HNO2) in aqueous chemical system spontaneously. The study showed that approximately 45 % of the current production and 20 % of the total denitrification was decreased at a FNA concentration of 0.0014 ± 0.0001 mg HNO2 – N L−1 with an equivalent nitrite concentration of 6.2 ± 0.9 mg NO2- - N L−1.ConclusionsThe novel biological process indicates the potential of using denitrifying bio-cathode MFC for green energy production.

A new clean approach for production of cobalt dihydroxide from aqueous Co(II) using oxygen-reducing biocathode microbial fuel cells

Abstract Cobalt recovery from aqueous Co(II) is one critical step for recovery of cobalt and recycle of spent lithium ion batteries, but suffers from consumption of large amount of energy and chemicals. Effective and environmental friendly processes are thus needed to improve the existing process limitations. This study proposes a new approach for cobalt dihydroxide production using oxygen-reducing biocathode microbial fuel cells (MFCs) with respect to aqueous Co(II) utilization and clean production. OH− generated from oxygen-reducing biocathodes in situ reacted with Co(II) to form precipitated Co(OH)2, achieving cobalt dihydroxide production with simultaneous electricity generation. The highest cobalt recovery rate of 0.079 ± 0.001 mmol/(L·h) and cobalt dihydroxide yield of 0.24 ± 0.00 mol/mol COD with simultaneous electricity production of 1.5 W/m3 were obtained under the optimal condition of a dissolved oxygen of 0.031 mM, an initial pH of 5.6, and an initial Co(II) concentration of 0.508 mM. These results demonstrate that cobalt dihydroxide production from aqueous Co(II) using oxygen-reducing biocathode MFCs may be a promising process for recovery of cobalt and recycle of spent lithium ion batteries as well as power generation.