Electrical Current Production Research Articles

Customizing the luminescent properties of compositionally disordered ceramics (Gd, Y, Yb, Tb, Ce)3Al2Ga3O12: From an ultra-fast scintillator to bright, wide-spectrum phosphor

A series of (Gd, Y, Yb, Tb, Ce)3Al2Ga3O12 compositionally disordered compounds with a garnet structure were prepared in the form of ceramics by sintering in oxygen at 1650 °C for 2 h and studied for the luminescent properties and interaction of ions entering the matrix host. The luminescence features of Ce3+ ions were found to be strongly dependent on the Yb concentration. Photoluminescence and scintillation kinetics are characterized by subnanosecond kinetics when the Yb index in the compound exceeds X = 0.3. It opens an opportunity to create an extremely fast and dense scintillation material emitting in a visible range. A further decrease in the Yb index in the compound leads to an increase in the intensity of Yb3+ infrared (IR) emission, whereas Ce3+ and Tb3+ ions contribute to the luminosity of the material by overlapping intra- and intereconfiguration luminescence bands in the spectral range of 300–700 nm. This finding opens an opportunity to create converter materials tolerant to the corpuscular radiation of isotope sources, providing a high efficiency of electric current production when coupled with a silicon photovoltaic element. The compounds were engineered at the nanoscale level, providing control over electronic excitation transfer between luminescent ions.

Comparative Analysis of Loss Mechanism Localization in a Semi-2D SOEC Single Cell Modell: Non-Equilibrium Thermodynamics versus Monocausal-Based Approach

This study aims to theoretically analyze the local entropy production rate in a SOEC single cell at T = 1123.15 K and p = 1 bar. Local entropy rates signify loss mechanisms, crucial for cell design and optimization. A semi-2D SOEC model based on non-equilibrium thermodynamics is developed, supplemented by monocausal correlations for direct comparison. The model is validated using KeraCell III data and grid independence analysis. Simulations of electric current density, temperature, heat flow, and local entropy production for various SOEC operating modes are presented. Coupled transport mechanisms significance is discussed, highlighting the pronounced impact of the Peltier effect on heat flux and temperature. The importance of the Peltier effect in SOECs compared to SOFCs is emphasised. The effects of the Seebeck effect on the potential distribution are superimposed by the dominant ohmic losses in the electrolyte. The localization of entropy production rates shows for exothermic operation that 66.6% of the total losses are due to the predominantly dominant irreversible ion transport in the electrolyte, while the entanglements in the reaction layers contribute 33% and GDLs less than 1%.

The Effect of Septage Sludge and Oxidizing Agents in the Microbial Fuel Cells Generating Electricity

Earlier research demonstrated the efficacy of microbial fuel cells in both wastewater treatment and renewable electric current generation. In this process, microbial fuel cells harness the potential of wastewater as a substrate and energy source, enabling microorganisms to generate electric current. Introducing microorganisms sourced from septage sludge acts as a microbial catalyst. Additionally, tofu wastewater is employed as a nutritional resource to support the growth of these microorganisms. A dual-chamber reactor was utilized to carry out this study, featuring an anode and a cathode connected through a salt bridge. Various substrate variations were performed on the anode, specifically with a combination of tofu liquid waste and septage sludge at ratios of 1:1, 1:2, and 1:3. Additionally, different electrolyte solutions, such as KMnO4 and K3(Fe(CN)6), were used at the cathode. Using different electrolyte solutions as electron acceptors can enhance the electric current production generated. The study spanned 240 hours of operation, during which electric current, voltage, COD, and BOD measurements were taken at 48-hour intervals. The findings revealed that including septage sludge in a 1:3 ratio yielded the highest current strength compared to other substrate variations, measuring 16.34 mA. When using a 0.25 M KMnO4 as an electrolyte solution, the voltage recorded was 8.78 V. Additionally, the most effective removal of COD and BOD content was achieved with a substrate ratio of 1:3 in the presence of KMnO4, achieving removal rates of 95.12% and 96.45%, respectively. These results indicate that adding septage sludge contributes to increased electricity current production.

Photosynthetic Fuel Cells: Just an Interesting Concept or a Promise for Future Technology?

The increasing concern about future environmental disasters as a result of global climate change is driving the efforts to develop novel clean energy technologies that will replace combustible fuels. A promising approach is the utilization of native photosynthesis as an electron source in bio-electrochemical cells. Over the past few years, there have been numerous descriptions of technologies for electrical current production using isolated photosynthetic complexes or membranes, intact microorganisms, or microorganism tissues in different electrochemical setups. In this review, we summarize these methods, and address the key factors that influence photocurrent generation and how can they be improved. Finally, we discuss the potential of photosynthetic-based bioelectricity production to become a real applicative solution that will be able to compete with existing technologies such as solar cells.

Exploring the Impact of Ni Doping on Bagasse Biochar and Its Efficient Hydrogen Production via Assisted Water Electrolysis

Heteroatom doping in carbon matrices has been widely used to prepare efficient carbonaceous electrocatalysts. Biochar‐assisted water electrolysis (BAWE) is a promising hydrogen production method that can efficiently utilize waste biomass. However, it is often limited by the slow anode biochar oxidation reaction (BOR). In addition, pure biochar typically lacks enough active catalytic sites; hence, its electrochemical reactivity is unsatisfactory. Herein, Ni is doped into bagasse biochar to improve its BOR. Its electrochemical properties and hydrogen production performance are measured using linear sweep voltammetry, electrochemical impedance spectroscopy, and chronopotentiometry. The reaction characteristics of the bagasse biochar are analyzed. The impact of its physiochemical properties on its oxidation process is discussed. Compared to the undoped biochar, the Ni‐doped biochar shows a larger specific surface area, a higher degree of graphitization, and stronger biochar oxidation reactivity (including a lower onset potential and larger electric current density), which significantly increase the electric current density and hydrogen production. This study provides a beneficial strategy for improving BAWE.

Photocurrent Production from Cherries in a Bio-Electrochemical Cell

In recent years, clean energy technologies that meet ever-increasing energy demands without the risk of environmental contamination has been a major interest. One approach is the utilization of plant leaves, which release redox-active NADPH as a result of photosynthesis, to generate photocurrent. In this work, we show for the first time that photocurrent can be harvested directly from the fruit of a cherry tree when associated with a bio-electrochemical cell. Furthermore, we apply electrochemical and spectroscopic methods to show that NADH in the fruit plays a major role in electric current production.

Screening of natural phenazine producers for electroactivity in bioelectrochemical systems.

Mediated extracellular electron transfer (EET) might be a great vehicle to connect microbial bioprocesses with electrochemical control in stirred-tank bioreactors. However, mediated electron transfer to date is not only much less efficient but also much less studied than microbial direct electron transfer to an anode. For example, despite the widespread capacity of pseudomonads to produce phenazine natural products, only Pseudomonas aeruginosa has been studied for its use of phenazines in bioelectrochemical applications. To provide a deeper understanding of the ecological potential for the bioelectrochemical exploitation of phenazines, we here investigated the potential electroactivity of over 100 putative diverse native phenazine producers and the performance within bioelectrochemical systems. Five species from the genera Pseudomonas, Streptomyces, Nocardiopsis, Brevibacterium and Burkholderia were identified as new electroactive bacteria. Electron discharge to the anode and electric current production correlated with the phenazine synthesis of Pseudomonas chlororaphis subsp. aurantiaca. Phenazine-1-carboxylic acid was the dominant molecule with a concentration of 86.1μg/ml mediating an anodic current of 15.1 μA/cm2 . On the other hand, Nocardiopsis chromatogenes used a wider range of phenazines at low concentrations and likely yet-unknown redox compounds to mediate EET, achieving an anodic current of 9.5μA/cm2 . Elucidating the energetic and metabolic usage of phenazines in these and other species might contribute to improving electron discharge and respiration. In the long run, this may enhance oxygen-limited bioproduction of value-added compounds based on mediated EET mechanisms.

Enhanced Exoelectrogenic Activity of Cupriavidus metallidurans in Bioelectrochemical Systems through the Expression of a Constitutively Active Diguanylate Cyclase

Electroactive bacteria have a wide range of applications, including electricity production, bioremediation, and the sensing of toxic compounds. Bacterial biofilm formation is often mediated by the second messenger cyclic guanosine monophosphate (c-di-GMP) synthesized by a diguanylate cyclase (DGC). The role of c-di-GMP in the expression of c-type cytochromes has been previously reported. The aim of this study was to determine the bioelectrogenic activity of Cupriavidus metallidurans strain CH34 pJBpleD*, which possesses a constitutively active DGC that increases c-di-GMP levels. Notably, the heterologous expression of the constitutively active DGC in C. metallidurans strain CH34 pJBpleD* showed a higher biofilm formation and increased the electrical current production up to 560%. In addition, C. metallidurans CH34 pJBpleD* showed increased levels of c-type cytochrome-associated transcripts compared with the wild-type strain CH34. Scanning electron microscopies revealed a denser extracellular matrix with an increased exopolymeric substance content in the CH34 pJBpleD* biofilm on the electrode surface. The results of this study suggest that higher levels of c-di-GMP synthesized by a constitutively active diguanylate cyclase in C. metallidurans strain CH34 pJBpleD* activated the formation of an electroactive biofilm on the electrode, enhancing its exoelectrogenic activity.

The mode of operation over time affects the capacitive properties of a packed anode biocapacitor

AbstractThe relationship between bioelectrochemical systems (BESs) and capacitors has been demonstrated through studies of BESs during intermittent operation. This type of BES has been named a microbial biocapacitor. This new energy storage device has been evaluated for short operational periods lasting for hours in most studies, which leaves open the question of long‐term operational feasibility for the biocapacitor. Moreover, the mode of BES operation before operation as a biocapacitor may determine the capacitive properties of the biofilm since activity or inactivity during electrical current production may affect biofilm response. In the present research, the effects of previous operational mode (rest in open circuit vs. potentiostatic current production) and operation time (seven tests in 94 days) on the capacitive properties of a biocapacitor were evaluated with key parameters such as capacitance, cell voltage, and volumetric current density. Correlations among parameters were analyzed to provide predictive equations for the packed anode biocapacitor. The equations showed that the capacitance increased after periods of biocapacitor inactivity and decreased after periods of activity, which led to equivalent variations in current density.

Electric current and heat production by a neutral carrier: an effect of the axion

A general axion-electrodynamic formalism is presented on the phenomenological level when the environment is dielectric (permittivity and permeability assumed to be constants). Thereafter, a strong and uniform magnetic field is considered in the z direction, the field region having the form of a long material cylinder (which corresponds to the haloscope setup). If the axion amplitude depends on time only, the axions give rise to an oscillating electric current in the z direction. We estimate the magnitudes of the azimuthal magnetic fields and the accompanying Joule heating in the cylinder, taking the cylinder to have ordinary dissipative properties. We evaluate and calculate the electric current and the heat production separately, without using the effective approximation, both when there is a strong magnetic field and when there is a strong electric one, showing that with the magnetic field there is a heat production, while with the electric field there is not. The heat generation that we consider, is a nontrivial effect as it is generated by the electrically neutral axions, and has obvious consequences for axion thermodynamics. The heat production can moreover have an additional advantage, since the effect is accumulative and so grows with time. The boundary conditions (in a classical sense) are explained and the use of them in a quantum mechanical context is discussed. This point is nontrivial, accentuated in particular in connection with the Casimir effect. For comparison purposes, we present finally some results for heat dissipation taken from the theory of viscous cosmology.

Current Production Capability of Drug-Resistant Pathogen Enables Its Rapid Label-Free Detection Applicable to Wastewater-Based Epidemiology.

A rapid and label-free method for the detection of drug-resistant pathogens is in high demand for wastewater-based epidemiology. As recently shown, the extent of electrical current production (Ic) is a useful indicator of a pathogen’s metabolic activity. Therefore, if drug-resistant bacteria have extracellular electron transport (EET) capability, a simple electric sensor may be able to detect not only the growth as a conventional plating technique but also metabolic activity specific for drug-resistant bacteria in the presence of antibiotics. Here, one of the multidrug-resistant pathogens in wastewater, Klebsiella pneumoniae, was shown to generate Ic, and the extent of Ic was unaffected by the microbial growth inhibitor, kanamycin, while the current was markedly decreased in environmental EET bacteria Shewanella oneidensis. Kanamycin differentiated Ic in K. pneumonia and S. oneidensis within 3 h. Furthermore, the detection of K. pneumoniae was successful in the presence of S. oneidensis in the electrochemical cell. These results clarify the advantage of detecting drug-resistant bacteria using whole-cell electrochemistry as a simple and rapid method to detect on-site drug-resistant pathogens in wastewater, compared with conventional colony counting, which takes a few days.

Improving stability of chloralkaline high-temperature PBI-PEMFCs

• Higher electric current production using Cl 2 -H 2 than O 2 -H 2 fuel cells. • Better performance of the cell at 120 °C with conventional Ru 0.75 Pt 0.25 O 2 catalyst. • New cathode outperforms Ru 0.75 Pt 0.25 O 2 catalyst within the range 140–180 °C. • Conventional cathode with Ru 0.75 Pt 0.25 O 2 breaks up after operation at 160 °C. • New electrode remains even after operation at 180 °C. This work focuses on the production of electricity using chloralkaline high temperature PEM fuel cells (HT-PEMFC) comparing, within the range 120–180 °C, the performance of a cell equipped with a cathode containing a novel Ru/Pt catalyst manufactured at mild temperature conditions with another cell which contains a conventional Ru based catalyst (Ru 0.75 Pt 0.25 O 2 ). Performance of the cell equipped with the conventional electrode at 120 °C is much better, but this situation reverses at higher operation temperatures, where the novel catalyst outperforms the conventional Ru 0.75 Pt 0.25 O 2 in terms of production of electricity. In addition, the new catalyst allows to operate even at 180 °C, temperature at which the cell equipped with the conventional electrode is completely deteriorated. Results pointed out that materials are the bottleneck for the chloralkaline HT-PEMFC technology but opens the window for the search of new materials that help to improve their future development.

Evaluation of electrical current production in microbial electrolysis cells fed with animal rendering wastewater

Anode-respiring bacteria (ARB) generate electrical current from the oxidation of short chain fatty acids (SCFA), primarily acetate, in microbial electrolysis cells (MECs). Animal rendering wastewater (RW) has high fat content, which under anaerobic conditions can yield acetate, making RW a potential feed for MECs. Yet, excess intermediate long chain fatty acids (LCFA) may limit conversion of LCFA and SCFA, and impact ARB activity. Here, we evaluated electrical current production in single-chamber MECs fed with RW. In RW-fed MECs, 34.26 ± 2.69% of the COD provided was converted to electrical current in an 80-day batch cycle. LCFA accumulated in RW-fed MECs, during which conversion of acetate to electrical current was limited. Diverse sulfate-reducing microorganisms were present in the anode biofilm in RW-fed MECs, whereas the genus Geobacter dominated in inoculum-only control MECs. Detection of H2-utilizing homoacetogens suggested some internal cycling of H2 produced at the cathode. Overall, this study shows that current production is possible from RW, but to be a viable process for RW treatment, further improvement in rates of COD conversion and current production is necessary along with identifying configurations and/or conditions in which the inhibitory effect of LCFA is reduced.

Modelisation and Optimization of a Microbial Desalination Cell System

In this work, we used a hybrid system composed of a Microbial Desalination Cell (MDC). This system allows, at the same time, the treatment of wastewater and the production of electrical energy for the desalination of saltwater. MDC is a cleaning technology used to purify wastewater. This process has been driven by converting organic compounds contained in wastewater into electrical energy through biological, chemical, and electrochemical processes. The produced electrical energy was used to desalinate the saline water. The objective of this work is the desalination or pre-desalination of seawater. For this, we have established a theoretical model consisting of differential equations describing the behavior of this system. Subsequently, we developed a program on MAT-LAB software to simulate and optimized the operation of this system and to promote the production of electrical energy in order to improve the desalination efficiency of the MDC. The theoretical result shows that the electrical current production is maximal when the methanogenic growth rate equal to zero, increases with the increasing of influent substrate concentration and the efficiency of desalination increased with flow rate of saline water.

Hydrogen production automatic control in continuous microbial electrolysis cells reactors used in wastewater treatment

In this paper, two control laws are proposed and applied in a model for a continuous Microbial Electrochemical Cells system. The used model is based on mass balances describing the behavior of substrate consumption, microbial growth, competition between anodophilic and methanogenic microorganisms for the carbon source in the anode, hydrogen generation, and electrical current production. The main control objective is to improve the electrical current generated and thus the production of bio-hydrogen gas in the reactor, using the dilution rate and the applied potential as individual control input variables. The control laws implemented are nonlinear adaptive type. In order to demonstrate its usefulness, numerical simulation runs involving multiple set-point changes and input perturbations were conducted for each control variable. The results of these simulations show that both control laws were able to respond adequately and efficiently to the disturbances and reach the reference value to which they were subjected. Moreover, it is possible to control both the electrical current produced and the hydrogen produced. Finally, these simulations also show that the highest rate of hydrogen production can be obtained using the applied potential as a control input, but such productivity is only attainable for a short period of time.

Allochthonous and Autochthonous Halothermotolerant Bioanodes From Hypersaline Sediment and Textile Wastewater: A Promising Microbial Electrochemical Process for Energy Recovery Coupled With Real Textile Wastewater Treatment.

The textile and clothing industry is the first manufacture sector in Tunisia in terms of employment and number of enterprises. It generates large volumes of textile dyeing wastewater (TDWW) containing high concentrations of saline, alkaline, and recalcitrant pollutants that could fuel tenacious and resilient electrochemically active microorganisms in bioanodes of bioelectrochemical systems. In this study, a designed hybrid bacterial halothermotolerant bioanode incorporating indigenous and exogenous bacteria from both hypersaline sediment of Chott El Djerid (HSCE) and TDWW is proposed for simultaneous treatment of real TDWW and anodic current generation under high salinity. For the proposed halothermotolerant bioanodes, electrical current production, chemical oxygen demand (COD) removal efficiency, and bacterial community dynamics were monitored. All the experiments of halothermotolerant bioanode formation have been conducted on 6 cm2 carbon felt electrodes polarized at −0.1 V/SCE and inoculated with 80% of TDWW and 20% of HSCE for 17 days at 45°C. A reproducible current production of about 12.5 ± 0.2 A/m2 and a total of 91 ± 3% of COD removal efficiency were experimentally validated. Metagenomic analysis demonstrated significant differences in bacterial diversity mainly at species level between anodic biofilms incorporating allochthonous and autochthonous bacteria and anodic biofilm containing only autochthonous bacteria as a control. Therefore, we concluded that these results provide for the first time a new noteworthy alternative for achieving treatment and recover energy, in the form of a high electric current, from real saline TDWW.

Three-dimensional graphitic mesoporous carbon-doped carbon felt bioanodes enables high electric current production in microbial fuel cells

Microbial fuel cells (MFCs) represent a new approach that can simultaneously enhance the treatment of waste streams and generate electricity. Although MFCs represent a promising technology for renewable energy production, they have not been successfully scaled-up mainly due to the relatively-low electricity generation and high cost associated with MFCs operation. Here, we investigated whether graphitic mesoporous carbon (GMC) decoration of carbon felt would improve the conductivity and biocompatibility of carbon felt anodes, leading to higher biomass attachment and electricity generation in MFCs fed with an organic substrate. To test this hypothesis, we applied 3 different GMC loading (i.e., 2, 5, and 10 mg/cm2 of anode surface area) in MFCs compared to control MFCs (with pristine carbon felt electrodes). We observed that the internal resistances of modified anodes with GMC were 1.2–2.3-order of magnitude less than pristine carbon felt anode, leading to maximum power densities of 70.3, 33.3, and 9.8 mW/m2 for 10, 5, and 2 mg/cm2-doped anode, respectively compared to only 3.8 mW/m2 for the untreated carbon felt. High-throughput sequencing revealed that increasing the GMC loading rate was associated with enriching more robust anode-respiring bacteria (ARB) biofilm community. These results demonstrate that 3-D GMC-doped carbon felt anodes could be a potential alternative to other expensive metal-based electrodes for achieving high electric current densities in MFCs fed with organic substrates, such as wastewater. Most importantly, high electron transfer capability, strong chemical stability, low cost, and excellent mechanical strength of 3-D GMC-doped carbon felt open up new opportunities for scaling-up of MFCs using cheap and high-performance anodes.

Stimulation of electricity production in microbial fuel cells via regulation of syntrophic consortium development

Production of electricity from wastewater in microbial fuel cells is possible due to the cooperation of hydrolytic, fermentative, and electrogenic microorganisms coexisting in a consortium. In this article, we present results that indicate that we can stimulate electrical current production from wastewater, from which power could not be produced without influencing the growth of a microbial consortium through preconditioning. The wood industry wastewater was thermally preconditioned at 45 °C before introducing it to microbial fuel cells which resulted in changing microbial consortium composition by the development of new species. In the anodes of microbial fuel cells that were fed preconditioned wastewater, we identified, by the means of metagenomic analysis, mixed fungi-bacteria syntrophic consortium that was capable of producing electricity from wood industry wastewater. The developed syntrophic consortium was dominated by fungi of the Trichocomaceae sp. and two bacteria species: Achromobacter insolitus and Geobacter sulfurreducens. None of these species were present in raw wastewater. Power was not generated in microbial fuel cells that were fed raw wastewater, but wastewater preconditioning stimulated power production at 0.33 W/m2 what responded to 1 A/m2 current density. The developed consortium decomposed cellulose present in wastewater into glucose and fermented it into acids and alcohols. We showed that stimulation of power production may be driven through substrate preconditioning before it is used in microbial fuel cells. By selecting growth conditions for a consortium, we may regulate its microbial composition and facilitate production of an electrical current from substrates that could not previously be used in microbial fuel cells.

Modulation of the Redox Potential and Electron/Proton Transfer Mechanisms in the Outer Membrane Cytochrome OmcF From Geobacter sulfurreducens.

The monoheme outer membrane cytochrome F (OmcF) from Geobacter sulfurreducens plays an important role in Fe(III) reduction and electric current production. The electrochemical characterization of this cytochrome has shown that its redox potential is modulated by the solution pH (redox-Bohr effect) endowing the protein with the necessary properties to couple electron and proton transfer in the physiological range. The analysis of the OmcF structures in the reduced and oxidized states showed that with the exception of the side chain of histidine 47 (His47), all other residues with protonatable side chains are distant from the heme iron and, therefore, are unlikely to affect the redox potential of the protein. The protonatable site at the imidazole ring of His47 is in the close proximity to the heme and, therefore, this residue was suggested as the redox-Bohr center. In the present work, we tested this hypothesis by replacing the His47 with non-protonatable residues (isoleucine – OmcFH47I and phenylalanine – OmcFH47F). The structure of the mutant OmcFH47I was determined by X-ray crystallography to 1.13 Å resolution and showed only minimal changes at the site of the mutation. Both mutants were 15N-labeled and their overall folding was confirmed to be the same as the wild-type by NMR spectroscopy. The pH dependence of the redox potential of the mutants was measured by cyclic voltammetry. Compared to the wild-type protein, the magnitude of the redox-Bohr effect in the mutants was smaller, but not fully abolished, confirming the role of His47 on the pH modulation of OmcF’s redox potential. However, the pH effect on the heme substituents’ NMR chemical shifts suggested that the heme propionate P13 also contributes to the overall redox-Bohr effect in OmcF. In physiological terms, the contribution of two independent acid–base centers to the observed redox-Bohr effect confers OmcF a higher versatility to environmental changes by coupling electron/proton transfer within a wider pH range.

Competitive exclusion in a DAE model for microbial electrolysis cells

Microbial electrolysis cells (MECs) are devices that employ electroactive bacteria to perform extracellular electron transfer, enabling hydrogen generation from biodegradable substrates. In our previous work, we developed and analyzed a differential-algebraic equation (DAE) model for MECs. The model resembles a chemostat or continuous stirred tank reactor (CSTR). It consists of ordinary differential equations for concentrations of substrate, microorganisms, and an extracellular mediator involved in electron transfer. There is also an algebraic constraint for electric current and hydrogen production. Our goal is to determine the outcome of competition between methanogenic archaea and electroactive bacteria, because only the latter contribute to electric current and the resulting hydrogen production. We investigate asymptotic stability in two industrially relevant versions of the model. An important aspect of many chemostat models is the principle of competitive exclusion. This states that only microbes which grow at the lowest substrate concentration will survive as t → ∞.We show that if methanogens can grow at the lowest substrate concentration, then the equilibrium corresponding to competitive exclusion by methanogens is globally asymptotically stable. The analogous result for electroactive bacteria is not necessarily true. In fact we show that local asymptotic stability of competitive exclusion by electroactive bacteria is not guaranteed, even in a simplified version of the model. In this case, even if electroactive bacteria can grow at the lowest substrate concentration, a few additional conditions are required to guarantee local asymptotic stability. We provide numerical simulations supporting these arguments. Our results suggest operating conditions that are most conducive to success of electroactive bacteria and the resulting current and hydrogen production in MECs. This will help identify when producing methane or electricity and hydrogen is favored.