Francesco Tadini-Buoninsegni, Ilaria Palchetti

Sensors • 0

<jats:p>Cancer is a multifactorial family of diseases that is still a leading cause of death worldwide. More than 100 different types of cancer affecting over 60 human organs are known. Chemotherapy plays a central role for treating cancer. The development of new anticancer drugs or new uses for existing drugs is an exciting and increasing research area. This is particularly important since drug resistance and side effects can limit the efficacy of the chemotherapy. Thus, there is a need for multiplexed, cost-effective, rapid, and novel screening methods that can help to elucidate the mechanism of the action of anticancer drugs and the identification of novel drug candidates. This review focuses on different label-free bioelectrochemical approaches, in particular, impedance-based methods, the solid supported membranes technique, and the DNA-based electrochemical sensor, that can be used to evaluate the effects of anticancer drugs on nucleic acids, membrane transporters, and living cells. Some relevant examples of anticancer drug interactions are presented which demonstrate the usefulness of such methods for the characterization of the mechanism of action of anticancer drugs that are targeted against various biomolecules.</jats:p>

Simeng Li, Gang Chen, Aavudai Anandhi

Energies • 0

<jats:p>Background: Bioelectrochemical systems (BESs) are emerging energy-effective and environment-friendly technologies. Different applications of BESs are able to effectively minimize wastes and treat wastewater while simultaneously recovering electricity, biohydrogen and other value-added chemicals via specific redox reactions. Although there are many studies that have greatly advanced the performance of BESs over the last decade, research and reviews on agriculture-relevant applications of BESs are very limited. Considering the increasing demand for food, energy and water due to human population expansion, novel technologies are urgently needed to promote productivity and sustainability in agriculture. Methodology: This review study is based on an extensive literature search regarding agriculture-related BES studies mainly in the last decades (i.e., 2009–2018). The databases used in this review study include Scopus, Google Scholar and Web of Science. The current and future applications of bioelectrochemical technologies in agriculture have been discussed. Findings/Conclusions: BESs have the potential to recover considerable amounts of electric power and energy chemicals from agricultural wastes and wastewater. The recovered energy can be used to reduce the energy input into agricultural systems. Other resources and value-added chemicals such as biofuels, plant nutrients and irrigation water can also be produced in BESs. In addition, BESs may replace unsustainable batteries to power remote sensors or be designed as biosensors for agricultural monitoring. The possible applications to produce food without sunlight and remediate contaminated soils using BESs have also been discussed. At the same time, agricultural wastes can also be processed into construction materials or biochar electrodes/electrocatalysts for reducing the high costs of current BESs. Future studies should evaluate the long-term performance and stability of on-farm BES applications.</jats:p>

Gabriele Beretta, Matteo Daghio, Anna Espinoza Tofalos et al.

Water • 0

<jats:p>Chromium is one of the most frequently used metal contaminants. Its hexavalent form Cr(VI), which is exploited in many industrial activities, is highly toxic, is water-soluble in the full pH range, and is a major threat to groundwater resources. Alongside traditional approaches to Cr(VI) treatment based on physical-chemical methods, technologies exploiting the ability of several microorganisms to reduce toxic and mobile Cr(VI) to the less toxic and stable Cr(III) form have been developed to improve the cost-effectiveness and sustainability of remediating hexavalent chromium-contaminated groundwater. Bioelectrochemical systems (BESs), principally investigated for wastewater treatment, may represent an innovative option for groundwater remediation. By using electrodes as virtually inexhaustible electron donors and acceptors to promote microbial oxidation-reduction reactions, in in situ remediation, BESs may offer the advantage of limited energy and chemicals requirements in comparison to other bioremediation technologies, which rely on external supplies of limiting inorganic nutrients and electron acceptors or donors to ensure proper conditions for microbial activity. Electron transfer is continuously promoted/controlled in terms of current or voltage application between the electrodes, close to which electrochemically active microorganisms are located. Therefore, this enhances the options of process real-time monitoring and control, which are often limited in in situ treatment schemes. This paper reviews research with BESs for treating chromium-contaminated wastewater, by focusing on the perspectives for Cr(VI) bioelectrochemical remediation and open research issues.</jats:p>

Euntae Yang, K. Chae, In S. Kim

Journal of Chemical Technology &amp; Biotechnology • 2016

BACKGROUND Combining a forward osmosis membrane with a microbial fuel cell (OsMFC) has shown improved electricity generation compared with conventional MFCs due to the enhanced proton transport based on the osmotically driven water flux across the semi-permeable membrane. However, the impact of membrane materials on the performance of OsMFCs has yet to be systematically investigated. This study examines the characteristics of different semi-permeable membranes (cellulose triacetate (CTA) nonwoven (NW), CTA embedded support (ES), and polyamide (PA)), and then compares the performances of OsMFCs having these membranes. RESULTS The OsMFC having CTA ES exhibited the highest electricity generation (current: 1.62 mA; maximum power density: 0.64 W m−2) although CTA ES showed lower proton transport ability and higher mass transfer resistance compared with PA. These results were due to the fact that CTA ES is less permeable to oxygen, such that anaerobic anode bacteria in the OsMFC having CTA ES were less inhibited by oxygen diffusion through the membrane than PA. Similarly, the highest water flux (0.83 L m−2 h−1)) was observed for CTA ES, even though CTA ES had a lower water flux than PA in the FO test. CONCLUSION This study confirms that CTA ES a more suitable membrane for OsMFCs than either PA or CTA NW. © 2015 Society of Chemical Industry

S. Patwardhan, Nishit Savla, Soumya Pandit et al.

Applied Sciences • 2021

Nowadays, the world is experiencing an energy crisis due to extensive globalization and industrialization. Most of the sources of renewable energy are getting depleted, and thus, there is an urge to locate alternative routes to produce energy efficiently. Microbial fuel cell (MFC) is a favorable technology that utilizes electroactive microorganisms acting as a biocatalyst at the anode compartment converting organic matter present in sewage water for bioelectricity production and simultaneously treating wastewater. However, there are certain limitations with a typical stand-alone MFC for efficient energy recovery and its practical implementation, including low power output and high cost associated with treatment. There are various modifications carried out on MFC for eliminating the limitations of a stand-alone MFC. Examples of such modification include integration of microbial fuel cell with capacitive deionization technology, forward osmosis technology, anaerobic digester, and constructed wetland technology. This review describes various integrated MFC systems along with their potential application on an industrial scale for wastewater treatment, biofuel generation, and energy production. As a result, such integration of MFCs with existing systems is urgently needed to address the cost, fouling, durability, and sustainability-related issues of MFCs while also improving the grade of treatment received by effluent.

Yang Zhao, Liang Duan, Xiang-qi Liu et al.

Membranes • 2022

Osmotic microbial fuel cells (OsMFCs) are an emerging wastewater treatment technology in bioelectricity generation, organic substrate removal, and wastewater reclamation. To address this issue, proton-conductive sites were strengthened after using the forward osmosis (FO) membrane by reducing the membrane resistance. The mechanism of improving electricity generation was attributed mainly to the unique characteristics of the membrane material and the water flux characteristics of the FO membrane. In particular, only when the concentration of catholyte was greater than 0.3 M was the membrane resistance the main contributor to the overall internal resistance. Meanwhile, through the simulation of the concentration inside the membrane, the changes in the membrane thickness direction and the phase transition of the internal structure of the membrane from the dry state (0% water content) to the expansion state (>50%water content) were analyzed, which were influenced by the water flux, further explaining the important role of the membrane’s microenvironment in reducing the membrane impedance. This further opens a novel avenue for the use of OsMFCs in practical engineering applications.

Yuqin Lu, Jinmeng Liu, Xin-Hua Wang et al.

• 2018

In this study, a novel combined system for simultaneous recovery of bioelectricity and water from wastewater was developed by integrating anaerobic acidification and a forward osmosis (FO) membrane with a microbial fuel cell (AAFO-MFC). Conductivity was thought to be an important factor affecting the performance of the AAFO-MFC system. Thus, effects of conductivity on the performance of AAFO-MFC system in treating synthetic wastewater were investigated. The results indicated that a higher conductivity increased the bioelectricity production, owing to a reduction in the internal resistance. However, it resulted in a rapid decrease of FO water flux and a shorter operating time because of a severer membrane fouling. The conductivity had no impact on the water quality of the effluents. The total organic carbon (TOC) and total phosphorus (TP) concentrations in the FO permeate were less than 4 and 0.5 mg·L-1, respectively, at all conductivity levels. However, the rejection of the FO membrane for NH4+-N was lower at all conductivity levels. The optimal comprehensive performance of this system was obtained when the conductivity was maintained at 7-8 mS·cm-1. In this case, the AAFO-MFC system achieved continuous and relatively stable power generation, and the water flux of FO membrane was relatively stable during a long-term operation of approximately 29 days.

Hengliang Zhang, Liang Duan, Shilong Li et al.

Membranes • 0

<jats:p>Osmotic microbial fuel cells (OsMFCs) with the abilities to simultaneously treat wastewater, produce clean water, and electricity provided a novel approach for the application of microbial fuel cell (MFC) and forward osmosis (FO). This synergistic merging of functions significantly improved the performances of OsMFCs. Nonetheless, despite their promising potential, OsMFCs currently receive inadequate attention in wastewater treatment, water reclamation, and energy recovery. In this review, we delved into the cooperation mechanisms between the MFC and the FO. MFC facilitates the FO process by promoting water flux, reducing reverse solute flux (RSF), and degrading contaminants in the feed solution (FS). Moreover, the water flux based on the FO principle contributed to MFC’s electricity generation capability. Furthermore, we summarized the potential roles of OsMFCs in resource recovery, including nutrient, energy, and water recovery, and identified the key factors, such as configurations, FO membranes, and draw solutions (DS). We prospected the practical applications of OsMFCs in the future, including their capabilities to remove emerging pollutants. Finally, we also highlighted the existing challenges in membrane fouling, system expansion, and RSF. We hope this review serves as a useful guide for the practical implementation of OsMFCs.</jats:p>

Yang Zhao, Liang Duan, Xiang Liu et al.

Membranes • 0

<jats:p>As a new membrane technology, forward osmosis (FO) has aroused more and more interest in the field of wastewater treatment and recovery in recent years. Due to the driving force of osmotic pressure rather than hydraulic pressure, FO is considered as a low pollution process, thus saving costs and energy. In addition, due to the high rejection rate of FO membrane to various pollutants, it can obtain higher quality pure water. Recovering valuable resources from wastewater will transform wastewater management from a treatment focused to sustainability focused strategy, creating the need for new technology development. An innovative treatment concept which is based on cooperation between bioelectrochemical systems and forward osmosis has been introduced and studied in the past few years. Bioelectrochemical systems can provide draw solute, perform pre-treatment, or reduce reverse salt flux to help with FO operation; while FO can achieve water recovery, enhance current generation, and supply energy sources for the operation of bioelectrochemical systems. This paper reviews the past research, describes the principle, development history, as well as quantitative analysis, and discusses the prospects of OsMFC technology, focusing on the recovery of resources from wastewater, especially the research progress and existing problems of forward osmosis technology and microbial fuel cell coupling technology. Moreover, the future development trends of this technology were prospected, so as to promote the application of forward osmosis technology in sewage treatment and resource synchronous recovery</jats:p>

Chi Tran Nhu, Loc Do Quang, Chun-Ping Jen et al.

IEEE Sensors Letters • 2024

In this letter, a protein enrichment microfluidic platform with an integrated bioelectrochemical sensing system has been proposed and demonstrated for the first time, enabling protein preconcentration and detection. The proposed chip was composed of an electrochemical biosensor integrated into a preconcentrator with a dual-gate structure. The bioelectrochemical sensor had three electrodes, including working, counter, and reference electrodes. The working and counter electrodes were made of gold, while the reference electrode was made of Ag/AgCl. The preconcentrator was designed with three microchannels, with a main channel electrically connected to two subchannels through Nafion ion-selective membranes. The chip was fabricated using photolithography and soft lithography techniques. Ag and AgCl layers were deposited on the gold electrode to form the reference electrode. The Nafion membrane was created using the microflow patterning technique. Then, the gold electrode surface was modified to attach anti-albumin antibodies (anti-bovine serum albumin—anti-BSA) and form the biosensor. Bovine serum albumin–fluorescein isothiocyanate conjugate was specifically bound to anti-BSA through the protein preconcentration process at the biosensor area. The experimental results show that bovine serum albumin (BSA) proteins were concentrated successfully after applying potentials to the ends of the microchannels. The protein concentration increased 25 times after 80 s. The change in the electrochemical impedance spectroscopy (EIS) signal demonstrates the specific binding between BSA and anti-BSA on the electrode surface. In addition, the results also show the significant effectiveness of the protein preconcentration process for improving the binding ability and electrical signal amplification of the bioelectrochemical sensor. With the obtained results, a lab-on-a-chip system can be developed to quantify protein concentration and diagnose some cancer diseases.

Hanqing Fan, Yuxuan Huang, Ngai Yin Yip

Frontiers of Environmental Science &amp; Engineering • 2022

Ion-exchange membranes (IEMs) are utilized in numerous established, emergent, and emerging applications for water, energy, and the environment. This article reviews the five different types of IEM selectivity, namely charge, valence, specific ion, ion/solvent, and ion/uncharged solute selectivities. Technological pathways to advance the selectivities through the sorption and migration mechanisms of transport in IEM are critically analyzed. Because of the underlying principles governing transport, efforts to enhance selectivity by tuning the membrane structural and chemical properties are almost always accompanied by a concomitant decline in permeability of the desired ion. Suppressing the undesired crossover of solvent and neutral species is crucial to realize the practical implementation of several technologies, including bioelectrochemical systems, hypersaline electrodialysis desalination, fuel cells, and redox flow batteries, but the ion/solvent and ion/uncharged solute selectivities are relatively understudied, compared to the ion/ion selectivities. Deepening fundamental understanding of the transport phenomena, specifically the factors underpinning structure-property-performance relationships, will be vital to guide the informed development of more selective IEMs. Innovations in material and membrane design offer opportunities to utilize ion discrimination mechanisms that are radically different from conventional IEMs and potentially depart from the putative permeability-selectivity tradeoff. Advancements in IEM selectivity can contribute to meeting the aqueous separation needs of water, energy, and environmental challenges.

E. Çevik, Mustafa Buyukharman, H. Yildiz

Biotechnology and Bioengineering • 2019

In this study, gold electrodes (GE) were coated with conducting polymers to obtain a high photocurrent using cyanobacteria from a novel bioelectrochemical fuel cell. For this purpose, 4‐(4H‐ditiheno[3,2‐b:2',3'‐d]pyrol‐4‐yl) aniline and 5‐(4H‐dithieno[3,2‐b:2',3'‐d]pyrol‐4‐yl) napthtalane‐1‐amine monomers were coated on GE by performing an electropolymerization process. After that, gold nanoparticles (AuNP) were specifically modified by 2‐mercaptoethane sulfonic acid and p‐aminothiophenol to attach to the electrode surface. The conducting polymers GE coat was modified with functionalized AuNP using a cross‐linker. The resulting electrode structures were characterized by cyclic voltammetry and chronoamperometry under on‐off illumination using a fiber optic light source. Cyanobacteria Leptolyngbia sp. was added to the GE/conducting polymer/AuNP electrode surface and stabilized by using a cellulose membrane. During the illumination, water was oxidized by the photosynthesis, and oxygen was released. The released oxygen was electrocatalytically reduced at the cathode surface and a 25 nA/cm 2 photocurrent was observed in GE/ Leptolyngbia sp. After the electrode modifications, a significant improvement in the photocurrent up to 630 nA/cm 2 was achieved.

Nils Rohbohm, Tianran Sun, Ramiro Blasco-Gómez et al.

EES Catalysis • 0

<jats:p>Carbon oxidation reaction enables a membrane-less bioelectrochemical system for microbial electrosynthesis.</jats:p>

Rabialtu Sulihah Binti Ibrahim, Zainura Zainon Noor, Nurul Huda Baharuddin et al.

Chemical Engineering &amp; Technology • 2020

<jats:title>Abstract</jats:title><jats:p>Membrane bioreactors (MBR) have gained much attention due to their ability to achieve higher treatment efficiency. However, high external energy consumption in aeration for membrane fouling mitigation has been limiting their application. Microbial fuel cells (MFC) can ideally extract energy from wastewater in the form of electricity and reduce membrane fouling. Thus, the use of MFC‐MBR is rapidly expanding. However, the MFC‐MBR design and operation is not fully mature and further research is needed to optimize the process efficiency and enhance the applicability. This review gives an overview of recent studies on the performances of MFC‐MBR systems, regarding the design and configuration of the integrated system, irrespective of whether optimization was done or not in the operating system.</jats:p>

Kuo-Ti Chen, Min-Der Bai, Hui-Yun Yang et al.

Sustainable Environment Research • 2020

<jats:title>Abstract</jats:title><jats:p>In wastewater treatment, biological nitrogen removal is an important topic, and the optimal condition for it is a mesophilic environment. This study developed a thermophilic microbial fuel cells (thermo-MFCs) equipped with a hydrophobic membrane electrode to remove and recover ammonia and water from leachate. The results were compared with those of the mesophilic MFCs (meso-MFCs) and they show that the current and power densities for meso-MFCs are higher. The ammonia removal efficiencies of thermo-MFCs are 83% (closed circuit) and 60% (open circuit), higher than those of closed- and open-circuit meso-MFCs (48 and 38%, respectively). Water vapor, the main recovery water flux for the thermo-MFCs, provided 36.5 L m<jats:sup>− 2</jats:sup> d<jats:sup>− 1</jats:sup> using the closed-circuit mode without applied energy. Moreover, thermo-MFCs and meso-MFCs can be restored within 24 h even under inhibition by using 7200 mg L<jats:sup>− 1</jats:sup> ammonia. The proposed process presents an economic and ecofriendly method to not only recover water and ammonia from leachate but also alleviate ammonia inhibition.</jats:p>

Gowthami Palanisamy, Ajmal P. Muhammed, Sadhasivam Thangarasu et al.

Membranes • 0

<jats:p>Chitosan (CS), a promising potential biopolymer with exquisite biocompatibility, economic viability, hydrophilicity, and chemical modifications, has drawn interest as an alternative material for proton exchange membrane (PEM) fabrication. However, CS in its original form exhibited low proton conductivity and mechanical stability, restricting its usage in PEM development. In this work, chitosan was functionalized (sulfonic acid (-SO3H) groups)) to enhance proton conductivity. The sulfonated chitosan (sCS) was blended with polyvinylidene fluoride (PVDF) polymer, along with the incorporation of functionalized SiO2 (–OH groups), for fabricating chitosan-based composite proton exchange membranes to enhance microbial fuel cell (MFC) performances. The results show that adding functionalized inorganic fillers (fSiO2) into the membrane enhances the mechanical, thermal, and anti-biofouling behavior. From the results, the PVDF/sCS/fSiO2 composite membrane exhibited enhanced proton conductivity 1.0644 × 10−2 S cm−1 at room temperature and increased IEC and mechanical and chemical stability. Furthermore, this study presents a revolutionary way to generate environmentally friendly natural polymer-based membrane materials for developing PEM candidates for enhanced MFC performances in generating bioelectricity and wastewater treatment.</jats:p>

Xiufen Li, Shujun Mu, Yueping Ren et al.

Journal of Renewable and Sustainable Energy • 2017

<jats:p>In membrane-less sediment microbial fuel cell (SMFC) reactors, copper ions are easily transported to the domains of both the anode and the cathode. Due to the unexpected balance between the biological effect of copper on the anode microbes and its function as electron acceptors at the cathode, the behavior of copper in membrane-less SMFCs became unexpected. The results in this manuscript showed that the copper concentration of  ≤3 mg/l in membrane-less SMFC reactors presented a positive effect on electricity generation, whereas a level of &amp;gt;3 mg/l played inhibitory action. Electrochemical impedance spectroscopy showed that the copper concentration of  ≤3 mg/l reduced the apparent internal resistance of electrodes via improving the anode biofilm as well as the ohmic resistance of both electrodes. The concentration of copper ions experienced a decrease by up to 85.0%, due to the consumption as electron acceptors at the cathode, utilization/adsorption by biomass, and chemical precipitation.</jats:p>

Sumiao Pang, Yang Gao, Seokheun Choi

Advanced Energy Materials • 2018

<jats:title>Abstract</jats:title><jats:p>The fabrication and performance of a flexible and stretchable microbial fuel cell (MFC) monolithically integrated into a single sheet of textile substrate are reported. The single‐layer textile MFC uses <jats:italic>Pseudomonas aeruginosa</jats:italic> (PAO1) as a biocatalyst to produce a maximum power of 6.4 µW cm<jats:sup>−2</jats:sup> and current density of 52 µA cm<jats:sup>−2</jats:sup>, which are substantially higher than previous textile‐MFCs and are similar to other flexible paper‐based MFCs. The textile MFC demonstrates a stable performance with repeated stretching and twisting cycles. The membrane‐less single‐chamber configuration drastically simplifies the fabrication and improves the performance of the MFC. A conductive and hydrophilic anode in a 3D fabric microchamber maximizes bacterial electricity generation from a liquid environment and a silver oxide/silver solid‐state cathode reduces cathodic overpotential for fast catalytic reaction. A simple batch fabrication approach simultaneously constructs 35 individual devices, which will revolutionize the mass production of textile MFCs. This stretchable and twistable power device printed directly onto a single textile substrate can establish a standardized platform for textile‐based biobatteries and will be potentially integrated into wearable electronics in the future.</jats:p>

Yuqin Lu, Jia Jia, Hengfeng Miao et al.

Membranes • 0

<jats:p>An osmotic microbial fuel cell (OsMFC) using a forward osmosis (FO) membrane to replace the proton exchange membrane in a typical MFC achieves superior electricity production and better effluent water quality during municipal wastewater treatment. However, inevitable FO membrane fouling, especially biofouling, has a significantly adverse impact on water flux and thus hinders the stable operation of the OsMFC. Here, we proposed a method for biofouling mitigation of the FO membrane and further improvement in current generation of the OsMFC by applying a silver nanoparticle (AgNP) modified FO membrane. The characteristic tests revealed that the AgNP modified thin film composite (TFC) polyamide FO membrane showed advanced hydrophilicity, more negative zeta potential and better antibacterial property. The biofouling of the FO membrane in OsMFC was effectively alleviated by using the AgNP modified membrane. This phenomenon could be attributed to the changes of TFC–FO membrane properties and the antibacterial property of AgNPs on the membrane surface. An increased hydrophilicity and a more negative zeta potential of the modified membrane enhanced the repulsion between foulants and membrane surface. In addition, AgNPs directly disturbed the functions of microorganisms deposited on the membrane surface. Owing to the biofouling mitigation of the AgNP modified membrane, the water flux and electricity generation of OsMFC were correspondingly improved.</jats:p>

Yang Zhao, Yonghui Song, Liang Duan

Water • 0

<jats:p>Osmotic microbial fuel cells (OsMFCs) can integrate forward osmosis into microbial fuel cells (MFCs), which are able to perform organic elimination, bioenergy production, and high-class water abstraction from wastewater. However, it is not well understood how the unique feature of OsMFCs, i.e., water flux, helps improve current generation. Based on experimental studies and the Springer model theory, a new method for representing water transmission in OsMFC membranes is put forward that considers water transmission by electro-osmosis resulting from proton flux through the membrane and by osmosis resulting from osmotic pressure grades of water. In this research, osmotic water transmission is associated with the permeable differential pressure resulting from the ionic differential concentration in the membrane, and electro-osmotic water transmission is found to be proportional to the current density employed but irrelevant to the composition gradients. The net water transmission in OsMFC depends on the operation time and increases accordingly with higher current density and composition gradients. Furthermore, the membrane’s proton conductibility and water-transmission capabilities are significantly affected by the moisture content, which decreases from the negative electrode to the positive electrode in the OsMFC system. Increasing water flux with higher osmotic pressure and current density is therefore able to diminish the resistance of the membrane.</jats:p>

Jiseon You, Lauren Wallis, Nevena Radisavljevic et al.

Energies • 0

<jats:p>Towards the commercialisation of microbial fuel cell (MFC) technology, well-performing, cost-effective, and sustainable separators are being developed. Ceramic is one of the promising materials for this purpose. In this study, ceramic separators made of three different clay types were tested to investigate the effect of ceramic material properties on their performance. The best-performing ceramic separators were white ceramic-based spotty membranes, which produced maximum power outputs of 717.7 ± 29.9 µW (white ceramic-based with brown spots, 71.8 W·m−3) and 715.3 ± 73.0 µW (white ceramic-based with red spots, 71.5 W·m−3). For single material ceramic types, red ceramic separator generated the highest power output of 670.5 ± 64. 8 µW (67.1 W·m−3). Porosity investigation revealed that white and red ceramics are more porous and have smaller pores compared to brown ceramic. Brown ceramic separators underperformed initially but seem more favourable for long-term operation due to bigger pores and thus less tendency of membrane fouling. This study presents ways to enhance the function of ceramic separators in MFCs such as the novel spotty design as well as fine-tuning of porosity and pore size.</jats:p>

Thanh Ngoc-Dan Cao, Shiao-Shing Chen, Hau-Ming Chang et al.

Environmental Science: Water Research &amp; Technology • 0

<p>Water recovery from wastewater was accomplished simultaneously with electrical energy production by the novel integration of distillation membrane and microbial fuel cell to create a system called membrane distillation microbial fuel cell.</p>

Ebtesam El Bestawy, Adel Salah Abd El-Hameed, Eman Fadl

Scientific Reports • 0

<jats:title>Abstract</jats:title><jats:p>The main objective of the present study was to desalinate seawater using <jats:italic>Bacillus cereus</jats:italic> gravel biofilm and cellulose acetate (CA) membranes with and without silver nanoparticles (AgNPs) as a potent and safe disinfectant for the treated water. Six desalination trials (I, II, III, IV, V and VI) were performed using the proposed biofilm/cellulose membrane. Results confirmed that <jats:italic>Bacillus cereus</jats:italic> gravel biofilm (microbial desalination) is the optimal system for desalination of seawater. It could achieve 45.0% RE (initial salinity: 44,478 mg/L), after only 3 h compared to the other tested treatments. It could also achieve 42, 42, 57, 43 and 59% RE for TDS, EC, TSS, COD and BOD, respectively. To overcome the problem of the residual salinity and reach complete elimination of salt content for potential reuse, multiple units of the proposed biofilm can be used in sequence. As a general conclusion, the <jats:italic>Bacillus cereus</jats:italic> biofilm system can be considered as remarkably efficient, feasible, rapid, clean, renewable, durable, environmentally friendly and easily applied technology compared to the very costly and complicated common desalination technologies. Up to our knowledge, this is the first time microbial biofilm was developed and used as an effective system for seawater desalination.</jats:p>

Yuli Yang, Xiaojin Li, Xiaoli Yang et al.

RSC Advances • 0

<p>Membrane aeration consumes less energy and enhances coulombic efficiency compared to diffused aeration in a microbial fuel cell.</p>

Yang Zhao, Liang Duan, Xiang Liu et al.

Membranes • 0

<jats:p>The forward osmosis membrane (FO membrane) is an emerging wastewater treatment technology in bioelectricity generation, organic substrate removal and wastewater reclamation. Compared with traditional membrane materials, the FO membrane has a more uniform water content distribution and internal solution concentration distribution. In the past, it was believed that one of the important factors restricting power generation was membrane fouling. This study innovatively constructed a mass transfer model of a fouling membrane. Through the analysis of the hydraulic resistance coefficient and the salt mass transfer resistance coefficient, the driving force and the tendency of reverse salt flux during membrane fouling were determined by the model. A surprising discovery was that the fouling membrane can also achieve efficient power generation. The results showed that the hydraulic resistance coefficient of the fouling membrane increased to 4.97 times the initial value, while the salt mass transfer resistance coefficient did not change significantly. Meanwhile, membrane fouling caused concentration polarization in the FO membrane, which enhanced the reverse trend of salt, and the enhancement effect was significantly higher than the impact of the water flux decline caused by membrane pollution. This will make an important contribution to research on FO membrane technology as sustainable membrane technology in wastewater treatment.</jats:p>

Du Sun, C. Lv, Yilong Hua et al.

SSRN Electronic Journal • 2023

As an emerging versatile technology for separating uranium from uranium-containing wastewater (UCW), microbial fuel cell (MFC) offers a novel approach to UCW treatment. Its cathode is essential for the treatment of UCW. To thoroughly investigate the efficacy of MFC in treating UCW, investigations were conducted using MFCs with five materials (containing iron sheet (IP), stainless steel mesh (SSM), carbon cloth (CC), carbon brush (CB), and nickel foam (NF)) as cathodes. The results revealed that each MFC system performed differently in terms of carbon source degradation, uranium removal, and electricity production. In terms of carbon source degradation, CB-MFC showed the best performance. The best uranium removal method was NF-MFC, and the best electricity production method was carbon-based cathode MFC. Five MFC systems demonstrated stable performance and consistent difference over five cycles, with CC-MFC outperforming the others. Furthermore, SEM and XPS characterization of the cathode materials before and after the experiment revealed that a significant amount of U(IV) was generated during the uranium removal process, indicating that uranium ions were primarily removed by electrochemical reduction precipitation. This study confirmed that abiotic cathode MFC had a high UCW removal potential and served as a good guideline for obtaining the best cathode for MFC.

Qiao Yang, Yang Lin, Lifen Liu et al.

Water Science and Technology • 2017

A competitive sewage treatment technology should meet the standard of water quality requirement and accomplish recovery of potential energy. This study presents such a new system, with coupled membrane bioreactor-microbial fuel cell features, which can not only treat wastewater, but also recovers energy from wastewater by electricity generation, and form a new resource by photosynthesis while providing the dissolved oxygen by algae. Specifically, in the system, the MnO2/polyaniline is used to modify the stainless steel mesh and to function well as system membrane and cathode, with satisfactory filtration and catalysis performance. The system enables continuous wastewater treatment with stable pollutant removal and electricity generation. Under the membrane flux of 119.4 Lm-2 h-1, a maximum power density of 1.2 W m-3 can be achieved, the algae multiply 6.1 times, and satisfactory wastewater treatment effect is achieved.

W. Hsu, H. Tsai, Ying Huang

Journal of Nanomaterials • 2017

Microbial fuel cells (MFCs) generate low-pollution power by feeding organic matter to bacteria; MFC applications have become crucial for energy recovery and environmental protection. The electrode materials of any MFC affect its power generation capacity. In this research, nine single-chamber MFCs with various electrode configurations were investigated and compared with each other. A fabrication process for carbon-based electrode coatings was proposed, and Escherichia coli HB101 was used in the studied MFC system. The results show that applying a coat of either graphene or carbon nanotubes (CNTs) to a stainless steel mesh electrode can improve the power density and reduce the internal resistance of an MFC system. Using the proposed surface modification method, CNTs and graphene used for anodic and cathodic modification can increase power generation by approximately 3–7 and 1.5–4.5 times, respectively. Remarkably, compared to a standard MFC with an untreated anode, the internal resistances of MFCs with CNTs- and graphene-modified anodes were reduced to 18 and 30% of standard internal resistance. Measurements of the nine systems we studied clearly presented the performance levels of CNTs and graphene applied as surface modification of stainless steel mesh electrodes.

Taehui Nam, S. Son, Eojn Kim et al.

Environmental Engineering Research • 2018

Microbial fuel cell (MFC) is an innovative environmental and energy system that converts organic wastewater into electrical energy. For practical implementation of MFC as a wastewater treatment process, a number of limitations need to be overcome. Improving cathodic performance is one of major challenges, and introduction of a current collector can be an easy and practical solution. In this study, three types of current collectors made of stainless steel (SS) were tested in a single-chamber cubic MFC. The three current collectors had different contact areas to the cathode (P 1.0 cm; PC 4.3 cm; PM 6.5 cm) and increasing the contacting area enhanced the power and current generations and coulombic and energy recoveries by mainly decreasing cathodic charge transfer impedance. Application of the SS mesh to the cathode (PM) improved maximum power density, optimum current density and maximum current density by 8.8%, 3.6% and 6.7%, respectively, comparing with P of no SS mesh. The SS mesh decreased cathodic polarization resistance by up to 16%, and cathodic charge transfer impedance by up to 39%, possibly because the SS mesh enhanced electron transport and oxygen reduction reaction. However, application of the SS mesh had little effect on ohmic impedance.

Shimaa E Abd El-Hamid, Islam A Aly, Asmaa R. Heiba et al.

ECS Meeting Abstracts • 2024

Steels are the most used alloys worldwide as they have superior mechanical properties, such as ductility and elasticity. Stainless steel (SS) is used far and wide from infrastructure, households, vehicles, surgical equipment, and medical implants, to electrochemical applications such as supercapacitors, fuel cells, lithium-ion batteries, aqueous rechargeable batteries, and bioelectrochemical systems (BES)1 such as microbial fuel cells (MFCs)2 and microbial electrolysis cells (MECs)3. Even though oxidized stainless steel is a very effective electrode material for BES, it has a high risk of corrosion due to the removal of the protective Cr-based passive oxide layer4. Hereby, this research aims to investigate the corrosion behavior of anodized stainless steel (SS) 304 and 316 mesh in saline water for potential use in BES with high salinity and try to mitigate that corrosion behavior using biocompatible materials. The tested electrodes include SS304 and SS316 mesh before and after anodization (anodized SS, AN-SS), in comparison to AN-SS coated with double layers of graphene oxide (GOx) and poly(3,4-ethylenedioxythiophene) (PEDOT). SS 304 and 316 were anodized using selective leaching protocol to enhance the removal of the bioincompatible and insulating Cr-based layer. The removal of that layer makes SS more susceptible to dissolution and hence further protection is needed. Both GOx and PEDOT were selected to enhance the surface conductivity, biocompatibility, and corrosion resistance. GOx was synthesized using the electro-exfoliation of a graphite sheet at a constant voltage of 10.0 V in terephthalic acid + NaOH solution, followed by centrifuging at 3000 rpm to remove the large particles.5 After several cycles of washing, the freeze-dried GOx was mixed with Nafion for ink preparation, which was used to coat the An-SS using the spray coating method. The coated electrode was further covered with a PEDOT layer, using the chronpotentiometry electropolymerization method (2 mA/cm2, for 10, 30, or 60 min). Several characterization techniques such as SEM, EDX, XPS, FT-IT, Raman spectroscopy, XRD, and TEM, were used to characterize the physical and chemical structure of the coating materials and the the fabricated electrodes. The corrosion behavior was evaluated using potentiodynamic and potentiostatic methods. Based on the anodic polarization results, the corrosion, passivation, and breakdown (due to dissolution) regions were identified. In this presentation, the corrosion behavior (Ecorr, Icorr, breakdown potential, etc) of the studied electrodes will be correlated with their chemical and physical structures. References K.-B. Pu, J.-R. Bai, Q.-Y. Chen, and Y.-H. Wang, in Novel Catalyst Materials for Bioelectrochemical Systems: Fundamentals and Applications, ACS Symposium Series., vol. 1342, p. 165–184, American Chemical Society (2020) https://doi.org/10.1021/bk-2020-1342.ch008. A. A. Abbas, H. H. Farrag, E. El-Sawy, and N. K. Allam, Journal of Cleaner Production, 285, 124816 (2021). Y. Zhang, M. D. Merrill, and B. E. Logan, International Journal of Hydrogen Energy, 35, 12020–12028 (2010). P. Ledezma, B. C. Donose, S. Freguia, and J. Keller, Electrochimica Acta, 158, 356–360 (2015). H. S. Wang et al., Green Chem., 20, 1306–1315 (2018).

Istia Prianti Hidayati, Putty Ekadewi, R. Arbianti et al.

IOP Conference Series: Earth and Environmental Science • 2021

Microbial Electrolysis Cell (MEC) can be used to produce hydrogen gas from organic matter contained in wastewater. However, at the cathode of MECs, hydrogen production may be limited by methanogenesis wherein CO2 and hydrogen protons react to form methane and water. In this study, activated carbon (AC)-Fe was used as a catalyst coated onto SS mesh 304 cathode. AC-Fe/SS was chosen for its high surface area, good activity, and stability. The combination of AC-Fe on SS was expected to increase hydrogen production in MECs. Adsorption and phase inversion were chosen to coat AC-Fe mixture on SS. The research was carried out in a 100 mL MEC reactor with an operating time of 258 h. The produced hydrogen was analyzed for its purity by GC-TCD. Voltage measurements were carried out using a digital multimeter. Additionally, bacterial growth was analyzed by spectrophotometer. The highest fraction of hydrogen gas production was 60% without catalyst (uncoated) over only 0.08% with AC-Fe/SS. The highest value of optical density for bacterial growth was 0.611 for AC-Fe/SS, higher than 0.427 without catalyst. The highest current density was 99.11 mA/m2 for AC-Fe/SS and 59.52 mA/m2 without catalyst. The results suggested AC-Fe/SS coating allows for increased bacterial growth and voltage generation at the cost of an adverse effect on hydrogen gas production.

Jiawei Xie, Xinyi Zou, Yaofeng Chang et al.

SSRN Electronic Journal • 2022

Microbial electrolysis cell (MEC) has been existing problems such as poor applicability to real wastewater and lack of cost-effective electrode materials in the practical application of refractory wastewater. A hydrolysis-acidification combined MEC system (HAR-MECs) with four inexpensive stainless-steel and conventional carbon cloth cathodes for the treatment of real textile-dyeing wastewater, which was fully evaluated the technical feasibility in terms of parameter optimization, spectral analysis, succession and cooperative/competition effect of microbial. Results showed that the optimum performance was achieved with a 12 h hydraulic retention time (HRT) and an applied voltage of 0.7 V in the HAR-MEC system with a 100 μm aperture stainless-steel mesh cathode (SSM-100 μm), and the associated optimum BOD5/COD improvement efficiency (74.75 ± 4.32 %) and current density (5.94 ± 0.03 A·m-2) were increased by 30.36 % and 22.36 % compared to a conventional carbon cloth cathode. The optimal system had effective removal of refractory organics and produced small molecules by electrical stimulation. The HAR segment could greatly alleviate the imbalance between electron donors and electron acceptors in the real refractory wastewater and reduce the treatment difficulty of the MEC segment, while the MEC system improved wastewater biodegradability, amplified the positive and specific interactions between degraders, fermenters and electroactive bacteria due to the substrate complexity. The SSM-100 μm-based system constructed by phylogenetic molecular ecological network (pMEN) exhibited moderate complexity and significantly strong positive correlation between electroactive bacteria and fermenters. It is highly feasible to use HAR-MEC with inexpensive stainless-steel cathode for textile-dyeing wastewater treatment.

Xiaoli Ma, Zhifeng Li, Aijuan Zhou et al.

• 2017

In comparison to the transportation and storage of hydrogen, methane take advantages in the practical application, while the emerging termed as ‘biohythane’ could be alternative to pure hydrogen or methane in new form of energy recovery from microbial electrolysis cell (MEC). However, the cathodic catalyst even for biohythane still bothers the performance and cost of total MEC, herein, we fabricated the MEC reactor with surrounding stainless steel mesh (SSM) to investigate the feasibility of stainless steel mesh as an alternative to precious metal in biohythane production. The columbic efficiency (CE) of anode was around at 80%, representing the SSM would not limit the activity of anodic biofilm, the SEM image and ATP results accordingly indicated the anodic biofilm was mature and well-constructed. The main contribution of methanogens that quantified by qPCR belonged to the hydrogenotrophic group ( Methanobacteriales ) at cathode. The energy efficiency reached more than 100%, reached up to approximately 150%, potentially suggesting the energetic feasibility of the application to obtain biohythane with SSM in scale-up MEC. Benefiting from the likely tubular configuration, the ohmic resistance of cathode was very low, while the main limitation associated with charge transfer was mainly caused by biofilm formation. The total performances of SSM used in the tubular configuration for biohythane production provide an insight into the implementation of non-precious metal in future scale-up pilot with energy recovery.

Suman Bajracharya, Adolf Krige, Leonidas Matsakas et al.

Fermentation • 0

<jats:p>Acetate can be produced from carbon dioxide (CO2) and electricity using bacteria at the cathode of microbial electrosynthesis (MES). This process relies on electrolytically-produced hydrogen (H2). However, the low solubility of H2 can limit the process. Using metal cathodes to generate H2 at a high rate can improve MES. Immobilizing bacteria on the metal cathode can further proliferate the H2 availability to the bacteria. In this study, we investigated the performances of 3D bioprinting of Sporomusa ovata on three metal meshes—copper (Cu), stainless steel (SS), and titanium (Ti), when used individually as a cathode in MES. Bacterial cells were immobilized on the metal using a 3D bioprinter with alginate hydrogel ink. The bioprinted Ti mesh exhibited higher acetate production (53 ± 19 g/m2/d) at −0.8 V vs. Ag/AgCl as compared to other metal cathodes. More than 9 g/L of acetate was achieved with bioprinted Ti, and the least amount was obtained with bioprinted Cu. Although all three metals are known for catalyzing H2 evolution, the lower biocompatibility and chemical stability of Cu hampered its performance. Stable and biocompatible Ti supported the bioprinted S. ovata effectively. Bioprinting of synthetic biofilm on H2-evolving metal cathodes can provide high-performing and robust biocathodes for further application of MES.</jats:p>

Xiaoli Ma, Zhifeng Li, Aijuan Zhou et al.

Royal Society Open Science • 2017

<jats:p> In comparison to the transportation and storage of hydrogen, methane has advantages in the practical application, while the emerging product termed as ‘biohythane’ could be an alternative to pure hydrogen or methane in a new form of energy recovery from microbial electrolysis cell (MEC). However, the cathodic catalyst even for biohythane still bothers the performance and cost of total MEC. Herein, we fabricated the MEC reactor with surrounding stainless steel mesh (SSM) to investigate the feasibility of stainless steel mesh as an alternative to precious metal in biohythane production. The columbic efficiency (CE) of anode was around at 80%, representing the SSM would not limit the activity of anodic biofilm; the SEM image and ATP results accordingly indicated the anodic biofilm was mature and well constructed. The main contribution of methanogens that quantified by qPCR belonged to the hydrogenotrophic group ( <jats:italic>Methanobacteriales</jats:italic> ) at cathode. The energy efficiency reached more than 100%, reached up to approximately 150%, potentially suggesting the energetic feasibility of the application to obtain biohythane with SSM in scale-up MEC. Benefiting from the likely tubular configuration, the ohmic resistance of cathode was very low, while the main limitation associated with charge transfer was mainly caused by biofilm formation. The total performances of SSM used in the tubular configuration for biohythane production provide an insight into the implementation of non-precious metal in future scale-up pilot with energy recovery. </jats:p>

Maliheh Hosseinian, Ghasem Najafpour Darzi, Ahmad Rahimpour

Electroanalysis • 2019

<jats:title>Abstract</jats:title><jats:p>Nickel oxide nanoparticle (NiO−NP) and polypyrrole (PPy) composite were deposited on a Pt electrode for fabrication of a urea biosensor. To develop the sensor, a thin film of PPy−NiO composite was deposited on a Pt substrate that serves as a matrix for the immobilization of enzyme. Urease was immobilized on the surface of Pt/PPy−NiO by a physical adsorption. The response of the fabricated electrode (Pt/PPy−NiO/Urs) towards urea was analyzed by chronoamperometry and cyclic voltammetry (CV) techniques. Electrochemical response of the bio‐electrode was significantly enhanced. This is due to electron transfer between Ni<jats:sup>2+</jats:sup> and Ni<jats:sup>3+</jats:sup> as the electro‐catalytic group and the reaction between polypyrrole and the urease‐liberated ammonium. The fabricated electrode showed reliable and demonstrated perfectly linear response (0.7–26.7 mM of urea concentration, R<jats:sup>2</jats:sup>= 0.993), with high sensitivity (0.153 mA mM<jats:sup>−1</jats:sup> cm<jats:sup>−2</jats:sup>), low detection of limit (1.6 μM), long stability (10 weeks), and low response time (∼5 s). The developed biosensor was highly selective and obtained data were repeatable and reproduced using PPy‐NiO composite loaded with immobilized urease as urea biosensors.</jats:p>

Xinglan Cui, Qingdong Miao, Xinyue Shi et al.

Sustainability • 0

<jats:p>Microbial fuel cells (MFC) have considerable potential in the field of energy production and pollutant treatment. However, a low power generation performance remains a significant bottleneck for MFCs. Biochar and anatase are anticipated to emerge as novel cathode catalytic materials due to their distinctive physicochemical properties and functional group architectures. In this study, biochar was utilized as a support for an anatase cathode to investigate the enhancement of the MFC power generation performance and its environmental impact. The results of the SEM and XPS experiments showed that the biochar-supported anatase composites were successfully prepared. Using the new cathode catalyst, the maximum current density and power density of the MFC reached 164 mA/m2 and 10.34 W/m2, respectively, which increased by 133% and 265% compared to a graphite cathode (70.51 mA/m2 and 2.83 W/m2). The degradation efficiency of Cr (VI) was 3.1 times higher in the biochar-supported anatase MFC than in the graphite cathode. The concentration and pH gradient experiments revealed that the degradation efficiency of Cr (VI) was 97.05% at an initial concentration of 10 mg/L, whereas a pH value of two resulted in a degradation efficiency of 94.275%. The biochar-supported anatase composites avoided anatase agglomeration and provided more active sites, thus accelerating the cathode electron transfer. In this study, natural anatase and biochar were ingeniously combined to fabricate a green and efficient electrode catalyst, offering a novel approach for the preparation of high-performance positive catalysts as well as a sustainable, economical, and environmentally friendly method for Cr (VI) removal in aqueous solutions.</jats:p>

Glenn Quek, R. J. Vázquez, Samantha R McCuskey et al.

Advanced Materials • 2022

Microbial electrosynthesis—using renewable electricity to stimulate microbial metabolism—holds the promise of sustainable chemical production. A key limitation hindering performance is slow electron‐transfer rates at biotic–abiotic interfaces. Here a new n‐type conjugated polyelectrolyte is rationally designed and synthesized and its use is demonstrated as a soft conductive material to encapsulate electroactive bacteria Shewanella oneidensis MR‐1. The self‐assembled 3D living biocomposite amplifies current uptake from the electrode ≈674‐fold over controls with the same initial number of cells, thereby enabling continuous synthesis of succinate from fumarate. Such functionality is a result of the increased number of bacterial cells having intimate electronic communication with the electrode and a higher current uptake per cell. This is underpinned by the molecular design of the polymer to have an n‐dopable conjugated backbone for facile reduction by the electrode and zwitterionic side chains for compatibility with aqueous media. Moreover, direct arylation polycondensation is employed instead of the traditional Stille polymerization to avoid non‐biocompatible tin by‐products. By demonstrating synergy between living cells with n‐type organic semiconductor materials, these results provide new strategies for improving the performance of bioelectrosynthesis technologies.

E. Nwanebu, Boris Tartakovsky, Fabrice Tanguay-Rioux et al.

ECS Meeting Abstracts • 2024

The goal of this study was to evaluate the impact of NiFe-based metal alloys on the CO2 conversion to carboxylic acids and methane (CH4) in CO2-fed Microbial Electrosynthesis (MES) cells. First, the impact of transition metal alloys on CO2 conversion and product specificity was studied in a MES cell with a conductive polymer cathode with electrodeposited NiFeBi alloy. It was found that the presence of the NiFeBi alloy significantly decreased production of CH4 from 0.5 to 0.1 L (Lc d) – 1, suggesting that methanogenic activity was suppressed in the presence of NiFeBi. On the other hand, the production of carboxylic acids consisting mainly of acetate, propionate and butyrate increased. Specifically, acetate production, which represented 80% of the total carboxylic acids in the cathode liquid increased by 70% to 1.0 g(Lc d)-1. This initial study demonstrated that product selectivity can be influenced by electrodeposition of transition metal alloys such as NiFeBi. It might be preferable to achieve selective production of high value long chain carboxylic acids such as valerate and caproate instead of acetate. Accordingly, in the following experiments NiFeMn and NiFeSn alloys were electrodeposited on carbon felt cathodes and evaluated for enhanced CO2 conversion in MES cells. Both alloys enhanced CH4 production, which reached 0.8 L (Lc d)-1. However, there was no observable improvement in acetate production (0.2 – 0.5 g (Lc d)-1) or other higher chain carboxylic acids in comparison to NiFeBi – coated MES. It was suggested that by using a more biocompatible carbon-based support for alloy electrodeposition, it is possible to improve acetate, butyrate and caproate production. In addition, it is important to facilitate nutrient transport through the three-dimensional (3D) cathode. Limited transport of CO2, H2 and nutrients was identified as a potential rate-limiting factor when using carbon felt electrode. 3D-printed conductive polymer lattices were manufactured and electrodeposited with NiFeSn and NiFeMn alloys. The NiFeMn-coated lattice showed insignificant improvement in higher chain carbon production, however caproate concentration was increased five folds on NiFeSn-coated cathode. Also, electrochemical characterization demonstrated increased hydrogen evolution reaction rate over time. Nevertheless, the throughput of this product remained low at 0.1 g (Lc d)-1). These results indicate that the presence of the NiFe-based metal alloys significantly influenced the electron transfer efficiency from the cathodes to microbial electroactive biofilms leading to increased formation of carboxylic acids in the cathode liquid. Therefore, the next step is to design more efficient 3D conductive polymer lattice electrodeposited with NiFeSn metal alloy to increase CO2 conversion to longer chain carboxylic acids.

D. X. Cao, Hengjing Yan, V. Brus et al.

ACS Applied Materials &amp; Interfaces • 2020

In this work, we aim to provide a better understanding for the reasons behind electron transfer inefficiencies between electrogenic bacterium and the electrode in microbial fuel cells. We do so by using a self-doped conjugated polyelectrolyte (CPE) as the electrode surface, onto which Geobacter sulfurreducens is placed, then using conductive atomic force microscopy (C-AFM) to directly visualize and quantify the electrons that are transferring from the bacterium to the electrode, thereby helping us gain a better understanding for the overpotential losses in MFCs. In doing so, we obtain images that show G. sulfurreducens can directly transfer electrons to an electrode surface without the use of pili, and that overpotential losses are likely due to cell death and poor distribution or performance of the bacteria's haem groups. This unique combination of CPEs with C-AFM can also be used for other studies where electron transfer loss mechanisms need to be understood on the nanoscale, allowing for direct visualization of potential issues in these systems.