Bioelectrochemical Reactions Research Articles

Green synthesis of Carica papaya mediated silver nanoparticles: Characterization, antibacterial activity, and bioelectricity generation for sustainable applications in nanotechnology

This study presents a sustainable method for synthesizing silver nanoparticles (Ag NPs) using green Carica papaya extract (CPE) as a reducing and stabilizing agent. The green synthesis minimizes environmental impact and utilizes bioactive compounds in Carica papaya (CP), offering an economical and sustainable alternative. The goal is to employ CPE for the eco-friendly synthesis of Ag NPs, followed by comprehensive characterization, antibacterial evaluation, cytotoxicity against brine shrimp, and examination of bioelectricity generation. Locally sourced CP was boiled in deionized water, then cooled and filtered twice. The bio-reduction of silver ions to Ag NPs was confirmed by a color change when 45 mL of 0.005 M AgNO3 was mixed with 5 mL of CPE. Characterization through UV–vis absorption spectrophotometry (UV), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM), and Gas chromatography-mass spectrometry (GC–MS) analysis confirms the successful formation and consistent size distribution of Ag nanoparticles. CPE is a crucial reducing agent, as evidenced by a distinct UV-visible peak at 422 nm. X-ray crystal analysis verifies highly crystalline Ag NPs with a face-centered cubic lattice structure. The d-spacing values in SAED images are consistent with the results obtained from XRD. Antimicrobial effectiveness against Escherichia coli and Staphylococcus epidermidis is demonstrated. The study explores the bioelectricity generation potential of CPE-synthesized Ag NPs, indicating promising prospects for sustainable energy solutions. Preliminary experiments show the ability of the nanoparticles to catalyze bio-electrochemical reactions. This dual-benefit study underscores CPEs role in antibacterial properties and bioelectricity generation, laying the groundwork for further research in sustainable nanotechnology applicable to healthcare and energy sectors and contributing to the advancement of environmentally friendly technologies.

Controlling heme redox properties in peptide amphiphile fibers with sequence and heme loading ratio

Controlling the reduction midpoint potential of heme B is a key factor in many bioelectrochemical reactions, including long-range electron transport. Currently, there are a number of globular model protein systems to study this biophysical parameter; however, there are none for large polymeric protein model systems (e.g., the OmcS protein from G. sulfurreducens). Peptide amphiphiles, short peptides with a lipid tail that polymerize into fibrous structures, fill this gap. Here, we show a peptide amphiphile model system where one can tune the electrochemical potential of heme B by changing the loading ratio and peptide sequence. Changing the loading ratio resulted in the most significant increase, with values as high as −22 mV down to −224 mV. Circular dichroism spectra of certain sequences show Cotton effects at lower loading ratios that disappear as more heme B is added, indicating an ordered environment that becomes disrupted if heme B is overpacked. These findings can contribute to the design of functional self-assembling biomaterials.

A biocompatible electrode/exoelectrogens interface augments bidirectional electron transfer and bioelectrochemical reactions

Bidirectional electron transfer is about that exoelectrogens produce bioelectricity via extracellular electron transfer at anode and drive cytoplasmic biochemical reactions via extracellular electron uptake at cathode. The key factor to determine above bioelectrochemical performances is the electron transfer efficiency under biocompatible abiotic/biotic interface. Here, a graphene/polyaniline (GO/PANI) nanocomposite electrode specially interfacing exoelectrogens (Shewanella loihica) and augmenting bidirectional electron transfer was conducted by in-situ electrochemical modification on carbon paper (CP). Impressively, the GO/PANI@CP electrode tremendously improved the performance of exoelectrogens at anode for wastewater treatment and bioelectricity generation (about 54 folds increase of power density compared to blank CP electrode). The bacteria on electrode surface not only showed fast electron release but also exhibited high electricity density of extracellular electron uptake through the proposed direct electron transfer pathway. Thus, the cathode applications of microbial electrosynthesis and bio-denitrification were developed via GO/PANI@CP electrode, which assisted the close contact between microbial outer-membrane cytochromes and nanocomposite electrode for efficient nitrate removal (0.333 mM/h). Overall, nanocomposite modified electrode with biocompatible interfaces has great potential to enhance bioelectrochemical reactions with exoelectrogens.

Artificial and Biosynthetic Nanoparticles Boost Bioelectrochemical Reactions via Efficient Bidirectional Electron Transfer of Shewanella loihica.

Bioelectrochemical reactions using whole-cell biocatalysts are promising carbon-neutral approaches because of their easy operation, low cost, and sustainability. Bidirectional (outward or inward) electron transfer via exoelectrogens plays the main role in driving bioelectrochemical reactions. However, the low electron transfer efficiency seriously inhibits bioelectrochemical reaction kinetics. Here, a three dimensional and artificial nanoparticles-constituent inverse opal-indium tin oxide (IO-ITO) electrode is fabricated and employed to connect with exoelectrogens (Shewanella loihica PV-4). The above electrode collected 128-fold higher cell density and exhibited a maximum current output approaching 1.5mAcm-2 within 24h at anode mode. By changing the IO-ITO electrode to cathode mode, the exoelectrogens exhibited the attractive ability of extracellular electron uptake to reduce fumarate and 16 times higher reverse current than the commercial carbon electrode. Notably, Fe-containing oxide nanoparticles are biologically synthesized at both sides of the outer cell membrane and probably contributed to direct electron transfer with the transmembrane c-type cytochromes. Owing to the efficient electron exchange via artificial and biosynthetic nanoparticles, bioelectrochemical CO2 reduction is also realized at the cathode. This work not only explored the possibility of augmenting bidirectional electron transfer but also provided a new strategy to boost bioelectrochemical reactions by introducing biohybrid nanoparticles.

Assessing the Performance of Continuous-Flow Microbial Fuel Cells and Membrane Electrode Assembly with Electrodeposited Mn Oxide Catalyst

Microbial fuel cells (MFCs) are considered promising energy sources whereby chemical energy is converted into electricity via bioelectrochemical reactions utilizing microorganisms. Several factors affect MFC performance, including cathodic reduction of oxygen, electrode materials, cell internal and external resistances, and cell design. This work describes the effect of the catalyst coating in the air-cathode membrane electrode assembly (MEA) for a microbial fuel cell (MFC) prepared via electrodeposition of manganese oxide. The characterization of the synthesized air-cathode MFC, operating in a continuous mode, was made via electrochemical impedance spectroscopy (EIS) analyses for the determination of the intrinsic properties of the electrode that are crucial for scalability purposes. EIS analysis of the MFCs and of the MEA reveals that the anode and cathode contribute to polarization resistance by about 85% and 15%, respectively, confirming the high catalytic activity of the Mn-based air cathode. The maximum power density of the Mn-based cathode is about 20% higher than that recorded using a Pt/C electrode.

Construction of Solid Binding Peptide (SBP)-Fused Non-Native Chimeric Enzyme to Promote Bienzymatic Cascade Induced Bioelectrocatalysis

In nature, most enzymes form a multienzyme complex called “metabolon” in the cellular system. The natural metabolon has been evolved to increase the efficiency of multi-step biocatalysis involved in such conditions. Such principle of enzymatic cascade reaction could be applied to the system which mimics pertinent reaction in vitro. Especially, its pertaining to bioelectrocatalytic system is quite promising to enhance its performance in terms of electrical generation or biochemical production, depending on systematic applications. In the previous studies , it was abundantly reported that multi-enzymatic reaction has been utilized to generate higher electrical current via sequential enzymatic oxidation of substrates (e.g., methanol, glucose, etc.) in bioelectrochemical systems, and to operate biochemical production system utilizing multi-enzymic conversion or reduction reactions. However, it is still challenging to implement multi-step enzymatic reaction in the electrode platforms due to unmanageable regulations of inter-enzyme distance or electrical connection between enzymatic cofactor and electrode, during multi-enzyme co-immobilization on electrode surface.Herein, we intentionally design and construct variants of chimeric enzyme in which two enzymes, invertase (INV) and glucose dehydrogenase (GDH), are conjugated with peptide linkers. We expected that INV hydrolyzes sucrose into fructose and glucose, then glucose is oxidized at the catalytic subunit of GDH, releasing electrons toward the electrode. It also employed solid binding peptides (SBPs) fused to GDH in chimeric enzyme for the electrical connection of GDH-SBP and electrode. In order to accomplish the desired reaction with chimeric enzyme, we have conducted the following tests; 1) The recombinant plasmid harboring the genetic sequence of two enzymes with an in-between linker was constructed. 2) By production of chimeric proteins, the chain reaction efficiency of fusion constructs was compared depending on the length of the linker. 3) The gold binding peptide (GBP) was fused to sites (N- and C-terminus, or other sites) of the catalytic subunit of GDH. And finally, 4) the electron transfer rates were monitored and compared depending on the GBP tethering sites. Throughout the whole study, we found the factors affecting the occurrence of multienzyme cascade-based bioelectrochemical reactions and how to control these factors to improve the reaction efficiency Figure 1

Field Effect Transistor with Nanoporous Gold Electrode.

Nanoporous gold (NPG) has excellent catalytic activity and has been used in the recent literature on this issue as a sensor in various electrochemical and bioelectrochemical reactions. This paper reports on a new type of metal-oxide-semiconductor field-effect transistor (MOSFET) that utilizes NPG as a gate electrode. Both n-channel and p-channel MOSFETs with NPG gate electrodes have been fabricated. The MOSFETs can be used as sensors and the results of two experiments are reported: the detection of glucose and the detection of carbon monoxide. A detailed comparison of the performance of the new MOSFET to that of the older generation of MOSFETs fitted with zinc oxide gate electrodes is given.

Polyphasic Characterization of Geotalea uranireducens NIT-SL11 Newly Isolated from a Complex of Sewage Sludge and Microbially Reduced Graphene Oxide

Graphene oxide (GO), a chemically oxidized sheet of graphite, has been used as a conductive carbon carrier of microbes to boost various bioelectrochemical reactions. However, the types of microbes that can reduce GO have rarely been investigated. In this study, a strain of GO-reducing bacteria, named NIT-SL11, which was obtained from a hydrogel of microbially reduced GO and anaerobic sludge that converts sewage to electricity, was phylogenically identified as a novel strain of Geotalea uraniireducens. Considering the current lack of information on the electrogenic ability of the bacterium and its physicochemical and chemotaxonomic characteristics, the polyphasic characterization of the Geotalea uraniireducens strain NIT-SL11 was performed. NIT-SL11 utilized various organic acids, such as lactate, benzoate, and formate, as electron donors and exhibited respiration using GO, electrodes, fumarate, and malate. The strain contained C16:1ω7c and C16:0 as the major fatty acids and MK-8 and 9 as the major respiratory quinones. The complete genome of NIT-SL11 was 4.7 Mbp in size with a G+C content of 60.9%, and it encoded 80 putative c-type cytochromes and 23 type IV pili-related proteins. The possible extracellular electron transfer (EET) pathways of the strain were the porin-cytochrome (Pcc) EET pathway and type IV pili-based pathway.

The intensity of biofilm formation by heterotrophic bacteria isolated from soil ferrosphere

The intensity of biofilm formation by heterotrophic bacteria possessed ammonifying ability (Bacillus simplex ChNPU F1, Streptomyces canus NUChC F2, Streptomyces gardneri ChNPU F3), ammonifying and iron-reducing ability (Fictibacillus sp. ChNPU ZVB1) previously isolated from soil ferrosphere was studied. Methods used: indirect measurement of the biomass of the bacterial biofilm using the adsorption/desorption of crystal violet, the aggregation test (to determine aggregation properties), the salt aggregation test (to determine hydrophobicity). The correlation analysis between the intensity of biofilm formation and aggregation of strains showed a significant positive correlation. The studied strains of microorganisms did not show high adhesive properties, they were moderately-adhesive (B. simplex, S. canus and S. gardneri) and weakly-adhesive (Fictibacillus sp.). It is supposed that the role these bacteria in the microbial damage of materials is determined preferably by bioelectrochemical reactions (iron-reducing bacteria) and the production of corrosive and/or antimicrobial metabolites (ammonifying and iron-reducing bacteria), but not by the biofilms formation. The prospect of further research is to analyze the antagonistic properties and biofilm formation of heterotrophic bacteria under co-cultivation conditions, in particular, with sulfate-reducing bacteria.

(Invited) Applications of Novel Electrochemical Technologies for Sustainable Fuel/Chemical Production and Resources Recovery

Electrochemical processes offer R&D opportunities toward decarbonization and resource recovery for circular economics. Innovate material produced by advancing manufacture techniques further widens its applications. In this presentation, we will discuss electrochemical process designs and material innovation to address technical and economic challenges of separations in biochemical/ biofuel production, resources recovery, CO2 utilization and impaired water treatment. In separations, the electrically driven force enabling selective capture of charged species and/or in-situ aqueous pH manipulation provides high energy efficiency, low capital footprint and cost for industrial applications compared to other separation technologies, e.g., separations by pressure-driven, thermally driven and biological-related. The common practices known are electrodialysis (ED), electrodeionization (EDI), capacitive deionization (CDI), cation intercalation desalination (CID), and ion concentration polarization (ICP). In these techniques, concentrated ions are separated from the liquid energy use is correlated with the quantity of ions removed. Therefore, the selective target capture provides “fit-for-purpose” separations. Pressure-driven processes cannot tune salinity for fit-for-purpose quality desalination but are effective at organic and biological species removal that electrochemical processes are not able to do. Thermal-driven processes cannot tune salinity for fit-for-purpose quality but are effective at organic and biological species removal. Biological-related processes typically apply bioelectrochemical reactions via microbes and bacteria to drive the removal of ions from the solution. In biological processes, ions are removed from the water solution. The ability to produce fit-for-purpose water has not been explored with biological processes, but they can treat targeted organics and biologicals. Compared to the pressure-driven membrane separation technologies used most in industrial separations, applications of selective separations have increased in recent years and becomes important to address the challenges of technology adaptation to climate change. For examples, the production of biofuel and bio-products to reduce green-house gas emission from fossil fuel and the non-conventional water supply for water-energy nexus have required high energy efficient and cost effective separation technologies. Innovative electrochemical separations can provide transformational impacts in advancing selective separations for highly energy efficient, small capital footprints and low processing cost. It, thus, enables the paradigm-shift of using alternative fuels and water supplies for industrial applications. We will discuss the key process performance metrics, energy consumption and processing rate, of various electrochemical technologies applied in biorefinery, waste to energy and water energy nexus to separate charges species from “dilute” aqueous phase. The ions separation performance demonstrated from various aqueous streams include 1) Inorganic and organic salts removal/capture in lignin valorization. and from bioprocessing streams in biofuel production; 2) volatile fatty acid removal/capture as well as biogas purification from solid waste anaerobic digester for waste to energy; 3) selective desalination of hardness, alkalinity, silica, and ammonia from impaired water for cooling water supply; 4)Capture and delivery for CO2 utilization. Critical issues in process design and material property to achieve electrochemical separation rate and energy efficiency for economic viability will be discussed.

Biomass-Derived Carbon Anode for High-Performance Microbial Fuel Cells

Although microbial fuel cells (MFCs) have been developed over the past decade, they still have a low power production bottleneck for practical engineering due to the ineffective interfacial bioelectrochemical reaction between exoelectrogens and anode surfaces using traditional carbonaceous materials. Constructing anodes from biomass is an effective strategy to tackle the current challenges and improve the efficiency of MFCs. The advantage features of these materials come from the well-decorated aspect with an enriched functional group, the turbostratic nature, and porous structure, which is important to promote the electrocatalytic behavior of anodes in MFCs. In this review article, the three designs of biomass-derived carbon anodes based on their final products (i.e., biomass-derived nanocomposite carbons for anode surface modification, biomass-derived free-standing three-dimensional carbon anodes, and biomass-derived carbons for hybrid structured anodes) are highlighted. Next, the most frequently obtained carbon anode morphologies, characterizations, and the carbonization processes of biomass-derived MFC anodes were systematically reviewed. To conclude, the drawbacks and prospects for biomass-derived carbon anodes are suggested.

Development of Bio-Electrochemical Reactor for Groundwater Denitrification: Effect of Electric Current and Water Hardness

Nitrate-nitrogen (NO3-N) contaminating groundwater is an environmental issue in many areas, and is difficult to treat by simple processes. A bio-electrochemical reactor (BER) using copper wire and graphite plate was developed to purify the NO3-N-contaminated groundwater. The low (of 10 mA) and high (of 20 mA) electric currents were applied to the BERs, and various influent hardness levels from 20 to 80 mg/L as CaCO3 due to groundwater characteristics were supplied to clarify the total nitrogen removal efficiency and NO3-N removal mechanisms. In the BER-10, the bio-electrochemical reactions caused 85% of total nitrogen to be removed through heterotrophic and autohydrogenotrophic denitrification in the suspended sludge and biofilm. However, the chemical deposit occurring at the cathode from water hardness affected the decreasing denitrification performance; 12.6% of Mg and 8.8% of Ca elements were observed in the biofilm. The enhancement of electrochemical reactions in the BER-20 caused integrating electrochemical and bio-electrochemical reactions; the NO3-N was electrochemically reduced to NO2-N, and it was further biologically reduced to N2. A better total nitrogen removal of 95% was found; although, a larger deposit of Mg (22.8%) and Ca (10.8%) was observed. The relatively low dissolved H2 in the BER-20 confirmed that the deposit affected the decreasing gaseous H2 transfer and inhibition of autohydrogenotrophic denitrification in the suspended sludge. According to the microbial analysis, both heterotrophic and autohydrogenotrophic denitrification were obtained in the suspended sludge of both BERs; Nocadia (26.8%) was the most abundant genus in the BER-10, whereas Flavobacterium (27.1%) and Nocadia (25.0%) were the dominant genera in the BER-20.

Mathematical modeling and performance evaluation of a cathodic bi-population microfluidic microbial fuel cell

Microfluidic microbial fuel cell, as a novel achievement of miniature microbial fuel cell, can be used in various fields such as poison detection, biosensors, etc. To investigate the mass transport and bacterial distribution inside the microfluidic microbial fuel cell, an innovative two-dimensional numerical model of microfluidic microbial fuel cell is proposed in this paper. This model is built via finite element method and the growth of bi-population microorganisms (exoelectrogens and facultative anaerobic bacteria) are coupled into the bioelectrochemical reaction kinetics. The accuracy of the present model is ensured by comparing the simulation results with other studies. After that, the effects of pH, dissolved oxygen and electrode porosity on the cell performance and spatial distribution of microorganisms are explored. Conclusions indicate that the pH gradient caused by the accumulation of hydrogen ions and hydroxide ions inhibits the growth of bacteria and mainly affects the anode performance. Higher electrode porosity enhances substrate transport and facilitates microbial growth. However, the effective conductivity of porous electrodes decreases with increasing porosity, which increases ohmic loss. Therefore, MMFC achieves an optimal power density of 956 W m−3 at a porosity of 0.6. Higher dissolved oxygen concentration contributes to enhancing the performance of microfluidic microbial fuel cell. The proposed model can provide strategies for the optimal design of microfluidic microbial fuel cell.

An innovative model for biofilm-based microfluidic microbial fuel cells

Compared with traditional microbial fuel cells, the microfluidic microbial fuel cells have higher performance and energy efficiency due to their co-laminar flow characteristic and micro-scale structure. However, there are very few numerical studies on microfluidic microbial fuel cells, which makes it difficult to study the operating mechanism. In this study, a three-dimensional numerical model is developed to characterize and predict the comprehensive performance of a biofilm-based Y-typed microfluidic microbial fuel cell. Multiple physical fields, containing the bioelectrochemical reaction kinetics, mass transport, hydrodynamics and thermal equilibrium, are coupled in this model to investigate the effects of various parameters on cell performance. The model reliability is validated through the previous experiment. Simulation results reveal the non-linear performance trend of microfluidic microbial fuel cells with the augment of temperature. In addition, high fuel concentration can cause the substrate inhibition phenomenon and affect bacterial activity. Model applicability for different parametric analyses is emphasized by exploring the effect of ionic strength on cell performance. Finally, considering the catholyte diffusion, optimization strategies for energy efficiency are presented. The proposed numerical model can be helpful for the experimental guidance and optimal design of microfluidic microbial fuel cells.

What is the Role of Individual Species within Bidirectional Electroactive Microbial Biofilms: A Case Study on Desulfarculus baarsii and Desulfurivibrio alkaliphilus

AbstractDesulfarculus baarsii and Desulfurivibrio alkaliphilus are strictly anaerobic bacteria existing in marine sediments. D. baarsii gains energy through reducing sulphate and D. alkaliphilus is able to reduce elemental sulphur, thiosulphate and polysulphide in seawater. Both organisms were previously identified as key organisms in sediment derived, bidirectional electroactive biofilms. Here, we investigated the electrochemical performance of these two bacteria in bio‐electrochemical systems and their possible involvement in anodic and cathodic reactions. The results show that D. baarsii was unable to donate or accept electrons to/from an electrode, while D. alkaliphilus was able to catalyse both anodic and cathodic reactions and interact with the electrode through direct or potentially indirect electron transfer. Raman spectra of D. alkaliphilus electrode biofilms showed a high similarity to Geobacter sulfurreducens biofilms, including the specific bands of cytochromes b and c, explaining the electroactivity of D. alkaliphilus in bioelectrochemical reactions.

Bioelectricity generation from human urine and simultaneous nutrient recovery: Role of Microbial Fuel Cells

Urine is a ‘valuable waste’ that can be exploited to generate bioelectricity and recover key nutrients for producing NPK-rich biofertilizers. In recent times, improved and innovative waste management technologies have emerged to manage the rapidly increasing environmental pollution and to accomplish the goal of sustainable development. Microbial fuel cells (MFCs) have attracted the attention of environmentalists worldwide to treat human urine and produce power through bioelectrochemical reactions in presence of electroactive bacteria growing on the anode. The bacteria break down the complex organic matter present in urine into simpler compounds and release the electrons which flow through an external circuit generating current at the cathode. Many other useful products are harvested at the end of the process. So, in this review, an attempt has been made to synthesize the information on MFCs fuelled with urine to generate bioelectricity and recover value-added resources (nutrients), and their modifications to enhance productivity. Moreover, configuration and mode of system operation, and factors enhancing the performance of MFCs have been also presented.

Structure design of 3D hierarchical porous anode for high performance microbial fuel cells: From macro-to micro-scale

Microbial fuel cell (MFC) is a promising technology that can simultaneously achieve wastewater treatment and energy recovery, but its low power output cannot satisfy the practical application. The performance of bioanodes, determined by the materials and structure, significantly affects the power output of MFCs. Herein, a designing approach is proposed to obtain high-performance bioanodes with the optimized macro- and microstructural using three-dimensional (3D) printing technology and electropolymerization. Through adjusting the distribution of large pores (i.e., 0.7 mm) and small pores (i.e., 0.4 mm) in 3D electrodes, the bioanode possesses an optimized macrostructure with large specific surface areas for the attachment of electroactive bacteria and sufficient mass transfer for bioelectrochemical reaction. Then the surface of electrode is further modified with 3D polypyrrole/graphene oxide (PPy/GO) microstructure to facilitate the formation of biofilm and the electron transfer at the biological/inorganic interfaces. Consequently, the bioanode with optimized macro- and microstructure achieves a high power density of 22.4 ± 0.6 W/m2, which is 18.7 times higher than that of commercial carbon felt electrode. This study brings new insights to design bioanodes in MFCs, providing a promising practical prospect.

A mathematical model for CO2 conversion of CH4-producing biocathodes in microbial electrosynthesis systems

Microbial electrosynthesis systems are a novel device for simultaneous CO2 reduction and CH4 production, and the CH4-producing biocathode in this system is the key component. This work presents a mathematical model to insight into the process of CH4 production on the biocathode. The model couples bioelectrochemical reaction, charge balance, mass transfer, dissolution of gaseous CO2 and interconversion of hydrated CO2, H2CO3, HCO3− and CO32−. To our knowledge, this is the first theoretical report for CH4-producing biocathodes in microbial electrosynthesis systems. This model is capable of predicting the response of CH4-producing biocathodes with operating time under various conditions and describing the effects of different parameters on CH4 production. The results suggest that the most important processes which influence the performance of biocathodes are the interconversions of hydrated CO2, H2CO3 and HCO3−.

Operando Local pH Mapping of Electrochemical and Bioelectrochemical Reactions Occurring at an Electrode Surface: Effect of the Buffer Concentration

AbstractIn this study, we aim at demonstrating the possibility for operando quantification of the thickness of the boundary layer where pH changes are occurring upon electrochemical reactions accompanied with the production or consumption of H+ cations. Confocal fluorescent microscopy (CFM) is combined with two different pH sensitive fluorescent dyes, namely 3,4′‐dihydroxy‐3′,5′‐bis‐(dimethylaminomethyl)flavone (FAM345) and rhodamine‐6‐aniline (R6H). This is the first attempt to quantify the effect of the buffer concentration (quantification of layer thickness) on local pH changes produced by ascorbic oxidation and oxygen reduction reaction directly occurring at non‐modified graphite electrodes. In addition, the effect of buffer concentration was studied also with respect to local pH variations produced by bioelectrochemical reactions.

Wearable Biofuel Cells: Advances from Fabrication to Application

AbstractThe booming field of wearable devices has nourished progress in developing multifunctional wearable energy sources that can withstand deformations while maintaining their electrochemical functions. Unlike energy storage systems such as rechargeable batteries and supercapacitors, wearable biofuel cells (w‐BFCs) generate green electricity from energy‐dense carbon‐neutral fuels via highly efficient bioelectrochemical reactions, delivering excellent biocompatibility, remarkable environmental sustainability, and exceptional capability of miniaturization. These desirable merits give w‐BFCs great potential in the field of wearable applications. Moreover, emerging studies of w‐BFCs in self‐powered biosensing, controlled drug delivery, and wound dressings have greatly expanded their possible fields of application. Recent progress and strategies to accomplish flexible and stretchable w‐BFCs are summarized here. Novel materials and configurations with tailored features that can be employed to fabricate w‐BFCs are elaborated and discussed. Current applications and near‐future applications of w‐BFCs in health‐monitoring and medical treatment fields are outlined. Furthermore, challenges and perspectives regarding this emerging field of materials science and engineering are also emphasized.