Search

This study explores the efficient decolorization and complete mineralization of the diazo dye Evans blue, using an integrated aerobic bioreactor system coupled with a double-chamber microbial fuel cell (DCMFC) including a bio-cathode and acetate as a cosubstrate. The research addresses the environmental challenges posed by dye-laden industrial effluents, focusing on achieving high decolorization efficiency and understanding the microbial communities involved. The study utilized mixed strains of actinomycetes, isolated from garden compost, to treat initial dye concentrations of 100 mg/L and 200 mg/L. Decolorization efficiency and microbial community composition were evaluated using 16S rRNA sequencing, and electrochemical impedance spectroscopy (EIS) was used to assess anode and DCMFC resistance. The results demonstrated decolorization efficiencies ranging from 90 ± 2% to 98 ± 1.9% for 100 mg/L and from 79 ± 2% to 87% ± 1% for 200 mg/L. An anode resistance of 12.48 Ω indicated a well-developed biofilm and enhanced electron transfer. The microbial community analysis revealed a significant presence of Pseudomonadota (45.5% in dye-acclimated cultures and 32% in inoculum cultures), with key genera including Actinomarinicola (13.75%), Thermochromatium (4.82%), and Geobacter (4.52%). This study highlights the potential of the integrated DCMFC–aerobic system, utilizing mixed actinomycetes strains, for the effective treatment of industrial dye effluents, offering both environmental and bioenergy benefits. [ABSTRACT FROM AUTHOR]

This study explores the efficient decolorization and complete mineralization of the diazo dye Evans blue, using an integrated aerobic bioreactor system coupled with a double-chamber microbial fuel cell (DCMFC) including a bio-cathode and acetate as a cosubstrate. The research addresses the environmental challenges posed by dye-laden industrial effluents, focusing on achieving high decolorization efficiency and understanding the microbial communities involved. The study utilized mixed strains of actinomycetes, isolated from garden compost, to treat initial dye concentrations of 100 mg/L and 200 mg/L. Decolorization efficiency and microbial community composition were evaluated using 16S rRNA sequencing, and electrochemical impedance spectroscopy (EIS) was used to assess anode and DCMFC resistance. The results demonstrated decolorization efficiencies ranging from 90 ± 2% to 98 ± 1.9% for 100 mg/L and from 79 ± 2% to 87% ± 1% for 200 mg/L. An anode resistance of 12.48 Ω indicated a well-developed biofilm and enhanced electron transfer. The microbial community analysis revealed a significant presence of Pseudomonadota (45.5% in dye-acclimated cultures and 32% in inoculum cultures), with key genera including Actinomarinicola (13.75%), Thermochromatium (4.82%), and Geobacter (4.52%). This study highlights the potential of the integrated DCMFC–aerobic system, utilizing mixed actinomycetes strains, for the effective treatment of industrial dye effluents, offering both environmental and bioenergy benefits.

Aims: Banana peel (BP) waste is still underutilized in Malaysia, which can be used as source of renewable energy. Microbial fuel cell (MFC) is a device that utilizes biomass to convert chemical energy into electrical energy with help of the microbial catalysis. The present study evaluates the current generation of MFC supplemented with BP waste as substrate for Pseudomonas aeruginosa ATCC 27853. Methodology and results: The CHNS result shows that the C:N ratio of BP is 27:1 which is within the optimum C:N ratio for the microbial food requirement. Fluctuation of current increases as concentration of banana peel extract (BPE) decreases from 1:10, 1:20, 1:40 and 1:80, thus making 1:10 BPE optimum. Current fluctuation is related to microbial activity due to the sufficiency of nutrients which subsequently affect the performance of MFC. BPE and banana peel slurry (BPS) comparison shows that BPS is optimum. BPE reaches a maximum current of 3.91 µA in ascending phase which is higher compared to BPS (3.65 µA). In descending phase, BPE current drops to 2.31 µA compared to 2.98 µA of BPS. In stationary phase, BPS able to maintain a higher current compared to BPE. MFC maximum current was doubled to 6.52 µA when PEM was treated priorly. Conclusion, significance and impact of study: Besides exploring and improving the ability of MFC as an alternative for power production other than fossil fuel, this research also encourage society to fully utilize waste as a source of renewable energy instead of throwing it into garbage without productivity. [ABSTRACT FROM AUTHOR]

The substorm current wedge (SCW), the characteristic current system of Earth's substorms, has been suggested to be a collective effect of many "wedgelets," mesoscale currents carried by magnetotail flux tubes of strong magnetic fields called dipolarizing flux bundles (DFBs). Each wedgelet contains an asymmetric pair of field‐aligned currents (FACs) so the net FAC of many wedgelets can equal an SCW's FAC content. It is unclear, however, why a wedgelet's FAC is asymmetric. To explore the reason, we investigate how earthward‐traveling DFBs interact with ambient plasma because this interaction leads to their FACs. The interaction is manifested as the pressure and magnetic field distributions around DFBs, which we examine statistically using THEMIS data. The statistical distributions are consistent with an interplay between the DFB‐caused mesoscale perturbations and the global magnetotail configuration and favor the rise of wedgelets' asymmetric FACs. This result reveals the importance of cross‐scale coupling in SCW formation. Plain Language Summary: The electric current system of one of the most important energy release events in Earth's near‐space provides valuable information on how such events proceed. Previous studies showed that the current system consists of small elements with unexpected but necessary asymmetries. To understand how such asymmetries are formed, we examine the space plasma environment related to them using spacecraft data. The plasma environment suggests that the asymmetries arise from an interaction between small and global‐scale phenomena, indicating the importance of cross‐scale coupling in understanding the geospace. Key Points: We examine the statistical distribution of pressure and magnetic field strength around dipolarizing flux bundles (DFBs) using THEMIS dataAround a DFB in the dusk (dawn) sector of the magnetotail, the quantities are larger on its morning (evening) sideThis asymmetric distribution suggests an interplay between meso and global scales and favors asymmetric wedgelets as previously found [ABSTRACT FROM AUTHOR]

Abstract The substorm current wedge (SCW), the characteristic current system of Earth's substorms, has been suggested to be a collective effect of many “wedgelets,” mesoscale currents carried by magnetotail flux tubes of strong magnetic fields called dipolarizing flux bundles (DFBs). Each wedgelet contains an asymmetric pair of field‐aligned currents (FACs) so the net FAC of many wedgelets can equal an SCW's FAC content. It is unclear, however, why a wedgelet's FAC is asymmetric. To explore the reason, we investigate how earthward‐traveling DFBs interact with ambient plasma because this interaction leads to their FACs. The interaction is manifested as the pressure and magnetic field distributions around DFBs, which we examine statistically using THEMIS data. The statistical distributions are consistent with an interplay between the DFB‐caused mesoscale perturbations and the global magnetotail configuration and favor the rise of wedgelets' asymmetric FACs. This result reveals the importance of cross‐scale coupling in SCW formation.

Bioaugmentation with electrochemically active bacteria (EAB) has been suggested useful for improving the performance of bioelectrochemical systems (BESs) for sustainable energy generation, while its success is dependent on EAB introduced into the systems. Here we report on the isolation of a novel EAB, Geobacter sulfurreducens strain 60473, from microbes that colonized on an anode of a sediment microbial fuel cell. This strain is highly adhesive to graphite electrodes, forms dense biofilms on electrode surfaces, and generates high current densities in BESs. When microbial electrolysis cells (MECs) inoculated with paddy-field soil and fed starch as the major organic substrate were augmented with strain 60473, Geobacter bacteria predominantly colonized on anodes, and MEC performances, including current generation, hydrogen production and organics removal, were substantially improved compared to non-bioaugmented controls. Results suggest that bioaugmentation with electrode-adhesive EAB, such as strain 60473, is a promising approach for improving the performance of BESs, including MECs treating fermentable organics and biomass wastes., (Copyright © 2024 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.)

Shedding light on the interaction between inorganic nanoparticles (NPs) and living microorganisms is at the basis of the development of biohybrid technologies with improved performance. Au NPs have been shown to be able to improve the extracellular electron transfer (EET) in intact bacterial cells interfaced with an electrode; however, detailed information on the role of NP-surface properties in their interaction with bacterial membranes is still lacking. Herein, we unveil how the surface functionalization of Au NPs influences their interaction with photosynthetic bacteria, focusing on cell morphology, growth kinetics, NPs localization, and electrocatalytic performance. We show that functionalization of Au NPs with cysteine in the zwitterionic form results in a uniform NPs distribution in purple bacteria, specifically locating the NPs within the outer-membrane/periplasmic space of bacterial cells. These biohybrid cells, when coupled with an electrode, exhibit enhanced EET and increased (photo)current generation, paving the way for the future development of rationally designed biohybrid electrochemical systems.

The injection of directional currents in solids with strong optical fields has attracted tremendous attention as a route to realize ultrafast electronics based on the quantum-mechanical nature of electrons at femto- to attosecond timescales. Such currents are usually the result of an asymmetric population distribution imprinted by the temporal symmetry of the driving field. Here we compare two experimental schemes that allow control over the amplitude and direction of light-field-driven currents excited in graphene. Both schemes rely on shaping the incident laser field with one parameter only: either the carrier-envelope phase (CEP) of a single laser pulse or the relative phase between pulses oscillating at angular frequencies ω and 2ω, both for comparable laser parameters. We observe that the efficiency in generating a current via two-color-control exceeds that of CEP control by more than two orders of magnitude (7 nA vs. 18 pA), as the ω + 2ω field exhibits significantly more asymmetry in its temporal shape. We support this finding with numerical simulations that clearly show that two-color current control in graphene is superior, even down to single-cycle pulse durations. We expect our results to be relevant to experimentally access fundamental properties of any solid at ultrafast timescales, as well as for the emerging field of petahertz electronics.

[Display omitted] • Simulated microgravity increases the current generation of EAB. • Simulated microgravity increases EAB biomass and enriches Geobacter. • Simulated microgravity induces the changes in gene and protein of anodic biofilm. Electrochemically active bacteria (EAB) exhibit promising prospects for space exploration and life support systems. However, the effects of the space environment on EAB are unclear. In this study, the effects of simulated microgravity on the current generation of mixed-culture EAB were illustrated, and the underlying mechanism was elucidated. The results demonstrated that the electrochemical activity of mixed-culture EAB was enhanced, which was mainly due to the enrichment of Geobacter and the increase in EAB biomass. Additionally, the genes and proteins of the biofilm changed obviously under simulated microgravity conditions, including: I) genes related to signal transfer, II) genes related to cell wall synthesis, and III) genes related to riboflavin synthesis. This study first revealed the enrichment in EAB abundance, the increase in EAB biomass, and the promotion of current generation under simulated microgravity. [ABSTRACT FROM AUTHOR]

Power generation and charge storage devices are commonly uncoupled when it comes to the design of materials relevant for their fabrication. Here, it is demonstrated that the biotic–abiotic composite comprising the self‐doped conjugated polyelectrolyte CPE‐K and electrogenic bacteria Shewanella oneidensis MR‐1 can reversibly switch its function between electrical current generation in chronoamperometry mode (≈150 mA m−2) and electrochemical energy storage as a pseudocapacitor with a specific capacitance of up to 80 F g−1. Interconversion of desirable properties for the different functions is achieved by the simple addition and removal of Mg2+ in the bulk electrolyte. Potentiostatic, galvanostatic, and electrochemical impedance spectroscopy characterization, accompanied by imaging and cell viability tests, indicate that the modulation of properties is a result of reversible changes in CPE‐K macrostructures and in the number of living bacteria within the composite. The results show the possibility to realize an "on‐demand" switch between current generation and charge storage by one integrated "living" material. [ABSTRACT FROM AUTHOR]

Bacterial extracellular electron transport (EET) plays an important role in many natural and engineering processes. Some periplasmic non-heme redox proteins usually coexist with c-type cytochromes (CTCs) during the EET process. However, in contrast to CTCs, little is known about the roles of these non-heme redox proteins in EET. In this study, the transcriptome of Shewanella decolorationis S12 showed that the gene encoding a periplasmic sulfite dehydrogenase molybdenum-binding subunit SorA was significantly up-regulated during electrode respiration in microbial fuel cells (MFCs) compared with that during azo-dye reduction. The maximum current density of MFCs catalyzed by a mutant strain lacking SorA (ΔsorA) was 25% higher than that of wild strain S12 (20 vs. 16 μA/cm2). Both biofilm formation and the current generation of the anodic biofilms were increased by the disruption of sorA, which suggests that the existence of SorA in S. decolorationis S12 inhibits electrode respiration. In contrast, disruption of sorA had no effect on respiration by S. decolorationis S12 with oxygen, fumarate, azo dye, or ferric citrate as electron acceptors. This is the first report of the specific effect of a periplasmic non-heme redox protein on EET to electrode and provides novel information for enhancing bacterial current generation.

Copyright of Journal of Southeast University (English Edition) is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bacterial extracellular electron transport (EET) plays an important role in many natural and engineering processes. Some periplasmic non-heme redox proteins usually coexist with c -type cytochromes (CTCs) during the EET process. However, in contrast to CTCs, little is known about the roles of these non-heme redox proteins in EET. In this study, the transcriptome of Shewanella decolorationis S12 showed that the gene encoding a periplasmic sulfite dehydrogenase molybdenum-binding subunit SorA was significantly up-regulated during electrode respiration in microbial fuel cells (MFCs) compared with that during azo-dye reduction. The maximum current density of MFCs catalyzed by a mutant strain lacking SorA (Δ sorA) was 25% higher than that of wild strain S12 (20 vs. 16 μA/cm2). Both biofilm formation and the current generation of the anodic biofilms were increased by the disruption of sorA , which suggests that the existence of SorA in S. decolorationis S12 inhibits electrode respiration. In contrast, disruption of sorA had no effect on respiration by S. decolorationis S12 with oxygen, fumarate, azo dye, or ferric citrate as electron acceptors. This is the first report of the specific effect of a periplasmic non-heme redox protein on EET to electrode and provides novel information for enhancing bacterial current generation. [ABSTRACT FROM AUTHOR]

Electroactive biofilms (EBs) engage in complex electron transfer and storage processes involving intracellular and extracellular mediators with temporary electron storage capabilities. Consequently, electroactive biofilms exhibit pseudocapacitive behaviors during substrate degradation processes. However, comprehensive systematic research in this area has been lacking. This study demonstrated that the pseudocapacitive property was an intrinsic characteristic of EBs. This property represents dynamic-controlled electron transfer and is critical in current generation, unlike noncapacitive responses. Nontransient charge and discharge experiments revealed a correlation between capacitive charge accumulation and current generation in EBs. Additionally, analysis of substrate degradation suggested that the maximum power density ( P max ) changed with the kinetic constants of COD degradation, with pseudocapacitances of EBs directly proportional to P max . The interaction networks of key latent variables were evaluated through partial least-squares path modeling analysis. The results indicated that cytochrome c was closely associated with the formation of pseudocapacitance in EBs. In conclusion, pseudocapacitance can be considered a valuable indicator for assessing the complex electron transfer behavior of EBs. Pseudocapacitive biofilms have the potential to efficiently regulate biological reactions and serve as a promising carbon-neutral and renewable strategy for energy generation and storage. An in-depth understanding of the intrinsic property of pseudocapacitive behavior in EBs can undoubtedly advance the development of this concept in the future.

We develop a high-performance anode formed from carbonized cow dung for bioelectrochemical systems. Thermal gravimetric analysis showed that the CD carbonization process started at 300°C and ended at approximately 550°C; the weight was reduced by 51%. After a heat-treatment at 800°C for 2 h, the treated CD featured a good conductivity and a high specific surface area. The maximum current density of 11.74 ± 0.41 A m-2 was achieved by CD anode (heated at 800°C), which remained relatively stable from more than 10 days. This study shows that a valuable anode material can be produced through conversion of CD by high-temperature carbonization. This approach provides a new way to alleviate environmental problems associated with CD.

We develop a high-performance anode formed from carbonized cow dung for bioelectrochemical systems. Thermal gravimetric analysis showed that the CD carbonization process started at 300°C and ended at approximately 550°C; the weight was reduced by 51%. After a heat-treatment at 800°C for 2 h, the treated CD featured a good conductivity and a high specific surface area. The maximum current density of 11.74 ± 0.41 A m-2 was achieved by CD anode (heated at 800°C), which remained relatively stable from more than 10 days. This study shows that a valuable anode material can be produced through conversion of CD by high-temperature carbonization. This approach provides a new way to alleviate environmental problems associated with CD. [ABSTRACT FROM AUTHOR]

This study reports a high-performance 3D stainless-steel photoanode (3D SS photoanode) for bioelectrochemical systems (BESs). The 3D SS photoanode consists of 3D carbon-coated SS felt bioactive side and a flat α-Fe 2 O 3 -coated SS plate photoactive side. Without light illumination, the electrode reached a current density of 26.2 ± 1.9 A m −2 , which was already one of the highest current densities reported thus far. Under illumination, the current density of the electrode was further increased to 46.5 ± 2.9 A m −2 . The mechanism of the photo-enhanced current production can be attributed to the reduced charge-transfer resistance between electrode surface and the biofilm with illumination. It was also found that long-term light illumination can enhance the biofilm formation on the 3D SS photoanode. These findings demonstrate that using the synergistic effect of photocatalysis and microbial electrocatalysis is an efficient way to boost the current production of the existing high-performance 3D anodes for BESs. [ABSTRACT FROM AUTHOR]

Titanium is under consideration as a potential stable bio-anode because of its high conductivity, suitable mechanical properties, and electrochemical inertness in the operating potential window of bio-electrochemical systems; however, its application is limited by its poor electron-transfer capacity with electroactive bacteria and weak ability to form biofilms on its hydrophobic surface. This study reports an effective and low-cost way to convert a hydrophobic titanium alloy surface into a hydrophilic surface that can be used as a bio-electrode with higher electron-transfer rates. Pyrolytic gas of sewage sludge is used to modify the titanium alloy. The current generation, anodic biofilm formation surface, and hydrophobicity are systematically investigated by comparing bare electrodes with three modified electrodes. Maximum current density (15.80 A/m 2 ), achieved using a modified electrode, is 316-fold higher than that of the bare titanium alloy electrode (0.05 A/m 2 ) and that achieved by titanium alloy electrodes modified by other methods (12.70 A/m 2 ). The pyrolytic gas-modified titanium alloy electrode can be used as a high-performance and scalable bio-anode for bio-electrochemical systems because of its high electron-transfer rates, hydrophilic nature, and ability to achieve high current density. [ABSTRACT FROM AUTHOR]

In this study, a single-chamber bio-photoelectrochemical system (BPES), integrating advantages of bioelectrochemical system and photocatalysis process, is developed using a g-C 3 N 4 /BiOBr heterojunction photocathode for methyl orange (MO) degradation and simultaneous energy recovery. Photocatalytic activities of g-C 3 N 4 /BiOBr, g-C 3 N 4 and BiOBr are characterized by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra; and electrochemical activities of photocathodes are examined by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results show that with an applied voltage of 0.8 V and under simulated solar irradiation, MO decolorization with g-C 3 N 4 /BiOBr photocathode reaches 97.8% within 4 h, higher than those with g-C 3 N 4 (85.3%) and BiOBr (87.3%) photocathodes. Likewise, higher hydrogen production rate (143.8 L m −3 d −1 ) is observed using g-C 3 N 4 /BiOBr photocathode; while values for g-C 3 N 4 and BiOBr photocathodes are 124.3 L m −3 d −1 and 117.1 L m −3 d −1 , respectively. PL and EIS reveal that superior performance of g-C 3 N 4 /BiOBr photocathode can be attributed to more efficient separation of photogenerated electron-hole pairs, lower resistance and better charge transfer. Synergistic effect occurs among biological, electrochemical and photocatalytic processes in illuminated BPES for MO removal. Photocathode optimization and system stability evaluation are conducted. This study demonstrates that the BPES holds great potential for efficient refractory organics degradation and energy production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two 3D carbon felt anodes with engineering mesoscale structure are fabricated. • Power density and columbic efficiency are increased with the 3D anodes processing. • The active 3D anode biofilm is consisted of a number of functional bacteria. • The increased anode biomasses are achieved by using the 3D anodes. In this study, the engineering-oriented three-dimensional (3D) bioanode concept was applied, demonstrating that spiral-stairs-like/rolled carbon felt (SCF/RCF) configurations achieved good performances in air–cathode microbial fuel cells (ACMFCs). With the 3D anodes, ACMFCs generated significantly higher power densities of 1535 mW/m3 (SCF) and 1800 mW/m3 (RCF), compared with that of a traditional flat carbon felt anode (FCF, 315 mW/m3). The coulombic efficiency of 15.39 % at SCF anode and 14.34 % at RCF anode also is higher than the 7.93 % at FCF anode. The 3D anode ACMFCs exhibited favorable removal of chemical oxygen demand (96 % of SCF and RCF) and total nitrogen (97 % of SCF, 99 % of RCF). Further results show that three-dimensional anode structures could enrich more electrode surface biomass and diversify the biofilm microbial communities for promoting bioelectroactivity, denitrification, and nitrification. These results demonstrate that three-dimensional anodes with active biofilm is a promising strategy for creating scalable MFCs-based wastewater treatment system. [ABSTRACT FROM AUTHOR]

Bacteria biofilm plays a key role in current generation of microbial fuel cells (MFCs), especially for the start-up stage. However, the detailed mechanism of the biofilm promoting the power generation is not very clear so far, especially for those exoelectrogens who rely on the self-excreted electron mediators for extracellular electron transfer. In this work, a biofilm formation inhibitor—sodium houttuyfonate (SH) is used to build a “non-biofilm” anode of Pseudomonas aeruginosa ( P. aeruginosa ) without affecting the bacteria growth during the MFC operation. According to the comparison results of the “non-biofilm” anode and biofilm-covered anode on current generation, phenazines concentration variation and anodic electrocatalysis, the biofilm on the anode not only provides plenty of bacterial cells for catalysis but also promotes the interfacial phenazine redox reaction through accumulating the self-generated mediators on anode for fast interfacial electron transfer. This work proves that the biofilm assisted electron mediator accumulation will benefit such kind of exoelectrogens to sustain sufficient electron mediators for extracellular electron transfer. [ABSTRACT FROM AUTHOR]

How to lower recombination of photogenerated electons and holes for efficient pollutant degradation remains a critical challenge for widespread application of photocatalytic fuel cell (PFC). Herein, a PFC based on in-situ utilization of generated electricity for strengthening pollutant removal efficiency was developed. The system was operated in alternate charging and discharging (ACD) mode using a capacitor-based circuit. With the increase of switch time (T s ) from 1 min to 10 min, the rhodamine B (RhB) decolourization rate decreased from 0.05931 min −1 to 0.03879 min −1 with current densities decreasing from 2.58 ± 0.08 A m −2 to 1.86 ± 0.02 A m −2 , which were 133–223% higher than that obtained in continuous energy harvesting (CEH) mode (0.80 ± 0.02 A m −2 ). However, the average power densities increased from 22.2 ± 1.9 mW m −2 to 110.3 ± 3.7 mW m −2 , which were lower than that in CEH mode (154.0 ± 16.7 mW m −2 ). This improvement of current output at the expense of power output was beneficial to minimize the recombination of photogenerated charge carriers and improve RhB decolourization, suggesting the enhancement effect of ACD mode on pollutant degradation compared with CEH mode. This work demonstrates that the electricity produced by PFC could be reused to improve system performance, which also provided a promising avenue of PFC operation for better pollutants removal. [ABSTRACT FROM AUTHOR]

Titanium-dioxide (TiO 2 ) semi-conductors are promising for microbial-fuel-cell anodes, because they can accelerate the biodegradation of refractory organic pollutants while recovering electrical current. To make the coupling of TiO 2 photocatalysis and biodegradation a success, the anode’s biofilm must be protected from damage from reactive-oxygen species generated by photocatalysis. In this work, we first realized a photocatalytic bioanode using N-doped TiO 2 coated on macroporous carbon-foam that accumulated biofilm inside. Photocatalysis occurred on the outer surface, while bacteria were protected inside the foam matrix; this is a unique manifestation of intimately coupled photobiocatalysis (ICPB). Experiments focused on degradation of 4-chlorophenol (4-CP) and electrochemical characterization of the ICPB-anode. The illuminated photo-anode, non-photocatalytic bio-anode, and ICPB-anode achieved ∼10%, ∼28%, and ∼41% 4-CP degradation efficiency, respectively; clearly, the ICPB anode achieved the best performance for 4-CP removal. The corresponding mineralization efficiency of the ICPB-anode also was the highest, and current generation by the ICPB-anode was 50% greater than that of a bio-anode. Cyclic voltammetry showed that photocatalyst and biofilm had to be present together to achieve high current density, and it also suggested that the electron-transport activity of c -type cytochromes of anode-respiring bacteria played an essential role in the transport of electrons. [ABSTRACT FROM AUTHOR]

Aside from technological applications, steering non-equilibrium currents in electronicmatter delivers information on the system electric and magneticproperties and their relation to electronic correlation and the underlying symmetry of the electrons' confinement. This theoretical study demonstrates that optical vortices are a versatile tool for spatio-temporal generation of charge currents via resonant and stimulated Raman-type processes for semi-conductor-based nanostructures as well as for atoms, thereby the orbital angular momentum associated with the optical vortex plays a key role. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) have attracted great attentions due to their great application potentials, but the relatively low power densities of MFCs still hinder their widespread practical applications. Herein, we report that the current generation in MFCs can be boosted by an order of magnitude, simply by coating a hydrophilic and positively charged ionic liquid polymer (ILP) on carbon cloth (CC) or carbon felt (CF). The ILP coating not only can increase the bacterial loading capacity due to the electrostatic interactions between ILP and bacterial cells, but also can improve the mediated extracellular electron transfer between the electrode and the cytochrome proteins on the outer membrane of Shewanella putrefaciens cells. As a result, the maximum power density of a MFC equipped with the CF-ILP bioanode is as high as 4400±170 mW m −2 , which is amongst the highest values reported to date. This work demonstrates a new strategy for greatly boosting the current generation in MFCs. [ABSTRACT FROM AUTHOR]

Recovering useful resources from wastes represents a new approach of clean production with significant environmental and economic benefits. Ammonium nitrogen, which is an important inorganic contaminant and also a resource for fertilizer, can be removed and recovered from wastewater. As the first step of recovery, ammonium removal was successfully demonstrated in this study by using an innovative treatment system - osmotic microbial fuel cell (OsMFC). This OsMFC achieved the removal efficiency of 80.1 ± 2.0% with an anolyte flow rate of 0.4 mL min −1 . Current generation was a key driving force for ammonium ion movement and increasing current generation from 0 to 1.8 ± 0.1 A m −2 could greatly enhance the removal efficiency from 40.7 ± 2.4% to 85.3 ± 3.5%. When current generation was similar, water flux could contribute significantly to facilitating ammonium removal, and as a result the OsMFC exhibited 55.2 ± 6.5% higher ammonium removal with water flux of 1.3 ± 0.2 LMH than that without water flux. In addition, ion diffusion and ion exchange contributed to 17.3 ± 2.4% and 2.8 ± 0.1% of ammonium removal, respectively, with 35 g L −1 NaCl as a catholyte. The key challenges such as the exact mechanism of ammonium transport, disposal of ammonium residue after recovery, effects of draw solutes, and system scaling up have been identified and discussed. The results of this study will help to develop an efficient approach for NEW recovery (NEW: nutrient, energy and water) from wastewater. [ABSTRACT FROM AUTHOR]

The dairy industry like most other agro-industries generates strong wastewaters with high biological and chemical oxygen demands representing the high organic content. The let out of untreated wastewater may cause serious problems in terms of organic load on the local municipal sewage treatment systems. The study examined the mediator-less microbial fuel cell (MFC) for the treatment of whey wastewater with simultaneous current generation in the presence of E. coli. The maximum current generated using whey wastewater was 3.019-6.99 W/m2/d with a constant resistance of 10 O with 0.1 N potassium permanganate as catholyte with carbon and graphite as electrodes respectively. The graphite electrodes were able to produce more current when compared to the carbon electrodes. During the study a biomass concentration of 3.042 g/l with a CO2 production of 13-20 mg/l as NaCO3 and H2 production of 20-25 ml/d respectively were obtained. The distance between the electrode and the Proton Exchange Membrane (PEM) and the distance between the electrodes in case of the dual electrodes also played an important role in the power generation. SEM image evidences the bio-film formation on the electrodes that supported the power density and a COD removal of 91-98% was also obtained. This phenomenon could be utilized to design an inexpensive autonomous system consisting of graphite or carbon electrodes, an electrical load and a recordable voltmeter to track energy generation due to E. coli fermentations. In the near term, these fuel cells could be utilized as a research tool for metabolic studies where the current response of microbial fuel cells would be extremely useful. [ABSTRACT FROM AUTHOR]

The effect of poised anode potential on electricity production and tetrathionate degradation was studied in two-chamber flow-through electrochemical (ES) and bioelectrochemical systems (BES). The minimum anode potential (vs. Ag/AgCl) for positive current generation was 0.3 V in BES and 0.5 V in the abiotic ES. The anode potential required to obtain average current density above 70 mA m −2 was 0.4 V in BES and above 0.7 V in ES. ES provided higher coulombic efficiency, but the average tetrathionate degradation rate remained significantly higher in BES (above 110 mg L −1 d −1 ) than in the abiotic ES (below 35 mg L −1 d −1 ). This study shows that at anode potentials below 0.7 V, the electrochemical tetrathionate degradation is only efficient with microbial catalyst and that significantly higher tetrathionate degradation rates can be obtained with bioelectrochemical systems than with electrochemical systems at the tested anode potentials. [ABSTRACT FROM AUTHOR]

Geobacter species are capable of utilizing solid-state compounds, including anodic electrodes, as electron acceptors of respiration via extracellular electron transfer (EET) and have attracted considerable attention for their crucial role as biocatalysts of bioelectrochemical systems (BES's). Recent studies disclosed that anode potentials affect power output and anodic microbial communities, including selection of dominant Geobacter species, in various BES's. However, the details in current-generating properties and responses to anode potentials have been investigated only for a model species, namely Geobacter sulfurreducens. In this study, the effects of anode potentials on the current generation and the EET paths were investigated by cultivating six Geobacter species with different anode potentials, followed by electrochemical analyses. The electrochemical cultivation demonstrated that the G. metallireducens clade species (G. sulfurreducens and G. metallireducens) constantly generate high current densities at a wide range of anode potentials (≥0.3 or -0.2 V vs. Ag/AgCl), while the subsurface clades species (G. daltonii, G. bemidjensis, G. chapellei, and G. pelophilus) generate a relatively large current only at limited potential regions (-0.1 to -0.3 V vs. Ag/AgCl). The linear sweep voltammetry analyses indicated that the G. metallireducens clade species utilize only one EET path irrespective of the anode potentials, while the subsurface clades species utilize multiple EET paths, which can be optimized depending on the anode potentials. These results clearly demonstrate that the response features to anode potentials are divergent among species (or clades) of Geobacter. [ABSTRACT FROM AUTHOR]

Microbial electrochemical systems (MESs) are an emerging technology that utilizes electrochemically active bacteria (EAB) to accomplish the transformation between chemical energy and electricity. Electrode modification is expected to promote EAB biofilm formation and increase MES performance. However, typical methods for MES electrode modification depend on harsh reaction conditions, toxic agents, or complex operations. In the study, a green and simple method was established with in situ L-arginine electropolymerization. Results demonstrate L-arginine electrooxidation is the primary step of in situ L-arginine electropolymerization, and the optimal potential range is [+0.5; +2] V. The N content on the electrode surface is increased from 1.4 ± 0.2% to 11.8 ± 1.5% with electropolymerized L-arginine (PLA) formation, and the zeta potential is increased from −29.3 ± 4.6 mV to −6.7 ± 5.2 mV. Better electropositivity increases the electrostatic attraction between EAB and working electrode, resulting in a 60% increase in biofilm biomass. Higher biomass enhances MES performance, and the current generation is increased by 76%. These results demonstrate that PLA modification is capable to increase electrode electropositivity, promote biofilm formation, and increase MES performance. The study illuminates the feasibility of MES electrode modification with in situ amino acid electropolymerization, and provides a new prospect to improve MES performance. [Display omitted] • Electropolymerized L-arginine modification increases electrode electropositivity. • Electropolymerized L-arginine modification promotes electrochemically active bacteria adhesion and biofilm formation. • Electropolymerized L-arginine modification increases the current generation of microbial electrochemical systems. • L-arginine electropolymerization is an efficient way for the electrode modification of microbial electrochemical systems. [ABSTRACT FROM AUTHOR]

Bacterial extracellular electron transfer is one of the main bottlenecks in determining the efficiency of bioelectrochemical systems. Here, we report a photobioanode that combines carbon material with a photocatalyst (α-Fe 2 O 3 ), utilizing visible light to accelerate biofilm formation and extracellular electron transfer in bioelectrochemical systems. Cyclic voltammetric studies of this photobioanode revealed active electron transfer at the anode/biofilm interface. The charge-transfer resistance of the anode/biofilm was ca. 46.6 Ω, which is half that of the unmodified anode. In addition, the results of confocal laser scanning microscopy and bacterial community analysis indicate that the photobioanode and light can accelerate biofilm formation and enrich exoelectrogens. When equipped in photo-bioelectrochemical systems, the start-up time was shortened from about 2.5 days to 1.1 days. The maximum current density of photo-bioelectrochemical systems was almost twice that of a control bioelectrochemical system. In addition, the current density of the photo-bio-electrochemical cell (PBEC) showed almost no decrease after being subjected to 40 d of illumination. This photobioanode is therefore a cost-effective, energy-clean, environment-friendly anode with high electrocatalytic activity and long-term stability, which has broad prospects in various processes, including wastewater treatment, bioelectricity generation, bioelectricity synthesis, and hydrogen production. [ABSTRACT FROM AUTHOR]

This paper introduces a novel composite anode that uses light to enhance current generation and accelerate biofilm formation in bioelectrochemical systems. The composite anode is composed of 316L stainless steel substrate and a nanostructured α-Fe 2 O 3 photocatalyst (PSS). The electrode properties, current generation, and biofilm properties of the anode are investigated. In terms of photocurrent, the optimal deposition and heat-treatment times are found to be 30 min and 2 min, respectively, which result in a maximum photocurrent of 0.6 A m −2 . The start-up time of the PSS is 1.2 days and the maximum current density is 2.8 A m −2 , twice and 25 times that of unmodified anode, respectively. The current density of the PSS remains stable during 20 days of illumination. Confocal laser scanning microscope images show that the PSS could benefit biofilm formation, while electrochemical impedance spectroscopy indicates that the PSS reduce the charge-transfer resistance of the anode. Our findings show that photo-electrochemical interaction is a promising way to enhance the biocompatibility of metal anodes for bioelectrochemical systems. [ABSTRACT FROM AUTHOR]

This paper introduces a high-performance photo-microbial desalination cell (PMDC) based on photo-electrochemical interactions. The anode of the cell was successfully modified with nanostructured α-Fe 2 O 3 . The maximum current density of the PMDC during operation was 8.8 A m −2 at an initial salt concentration of 20 g L −1 , which was twice that of the unmodified microbial desalination cell. The results of electrochemical impedance spectroscopy and cyclic voltammetry indicated the current increase of PMDC was mainly contributed by the high electron transfer rate at electrode/biofilm interface. The salt concentration of the effluent from the middle chamber was below ca. 1.4 mg L −1 and the salt removal performance of the PMDC was always higher than 96%. The calculated number of harvested electrons agreed well with NaCl removal. In conclusion, the present PMDC effectively offers simultaneous electricity generation and desalination. [ABSTRACT FROM AUTHOR]

We study the optical response of a suspended, monolayer graphene field-effect transistor structure in magnetic fields of up to 9 T (quantum Hall regime). With an illumination power of only 3 μ W, we measure a photocurrent of up to 400 nA (without an applied bias) corresponding to a photo-responsivity of 0.13 A W ^−1 , which we believe to be one of the highest values ever measured in single-layer graphene. We discuss possible mechanisms for generating this strong photo-response (17 electron–hole pairs per 100 incident photons). Based on our experimental findings, we believe that the most likely scenario is a ballistic two-stage process including carrier multiplication via Auger-type inelastic Coulomb scattering at the graphene edge.

Geobacter species are capable of utilizing solid-state compounds, including anodic electrodes, as electron acceptors of respiration via extracellular electron transfer (EET) and have attracted considerable attention for their crucial role as biocatalysts of bioelectrochemical systems (BES’s). Recent studies disclosed that anode potentials affect power output and anodic microbial communities, including selection of dominant Geobacter species, in various BES’s. However, the details in current-generating properties and responses to anode potentials have been investigated only for a model species, namely Geobacter sulfurreducens. In this study, the effects of anode potentials on the current generation and the EET paths were investigated by cultivating six Geobacter species with different anode potentials, followed by electrochemical analyses. The electrochemical cultivation demonstrated that the G. metallireducens clade species (G. sulfurreducens and G. metallireducens) constantly generate high current densities at a wide range of anode potentials (≥−0.3 or −0.2 V vs. Ag/AgCl), while the subsurface clades species (G. daltonii, G. bemidjensis, G. chapellei, and G. pelophilus) generate a relatively large current only at limited potential regions (−0.1 to −0.3 V vs. Ag/AgCl). The linear sweep voltammetry analyses indicated that the G. metallireducens clade species utilize only one EET path irrespective of the anode potentials, while the subsurface clades species utilize multiple EET paths, which can be optimized depending on the anode potentials. These results clearly demonstrate that the response features to anode potentials are divergent among species (or clades) of Geobacter.