Biofuel Cell Electrodes Research Articles

Flexible and Stretchable Electrodes in Biofuel Cells for Sustainable Power

Flexible and Stretchable Electrodes in Biofuel Cells for Sustainable Power

Poly(m-phenylenediamine) based nanocomposite as high-performance biofuel cell electrode for renewable energy generation using environmentally friendly and biocompatible materials

There is a tremendous increase in the development of high performance environmentally friendly and biocompatible nanomaterials for several applications including biofuel cells. This study focuses on the fabrication of a bioanode by physical adsorption of an enzyme and the mediator on ternary nanocomposite, acting as a conducting support. The nanocomposite was obtained by in-situ polymerization of aniline’s derivative/poly(m-phenylenediamine) (mPDP), magnetic nanoparticles (NPs) (Fe3O4) and graphitic carbon nitride (g-CN). The Fe3O4 NPs were synthesised through green route using Neem leaves (Azadirachta indica) extracts via a hydrothermal process. Advanced analytical techniques including FTIR, XRD, TEM and SEM coupled with EDX were used to uncover the characteristics of these materials. Furthermore, the assessment of the modified glassy carbon electrodes (GCEs) was carried out by Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS) and Linear sweep voltammetry (LSV). The bioanode [Fe3O4/g-CN/mPDP/Ferritin (FRT)/Glucose oxidase (GOs)] modified with ternary nanocomposite delivered an excellent current density of ca. 9.2 mA cm−2 at ca. 50 mM glucose concentration by sweeping the voltage at 100 mVs−1. Moreover, the developed bioanode showed high open circuit voltage (ca. 0.59 V) with good electrocatalytic performance having immense potential for diverse electrochemical processes along with energy generation in biofuel cell applications.

Sustainably Sourced Mesoporous Carbon Molecular Sieves as Immobilization Matrices for Enzymatic Biofuel Cell Applications

Ordered mesoporous carbon CMK-3 sieves with a hexagonal structure and uniform pore size have recently emerged as promising materials for applications as adsorbents and electrodes. In this study, using sucrose as the sustainable carbon source and SBA-15 as a template, CMK-3 sieves are synthesized to form bioelectrocatalytic immobilization matrices for enzymatic biofuel cell (EFC) electrodes. Their electrochemical performance, capacitive features, and the stability of enzyme immobilization are analyzed and compared to commercially available multi-walled carbon nanotubes (MWCNT) using cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The anodic reaction in the presence of glucose oxidase (GOx) and ferrocene methanol (FcMeOH) on the sustainably sourced CMK-3-based electrodes produces bioelectrocatalytic current responses at 0.5 V vs. saturated calomel electrode (SCE) that are twice as high as on the MWCNT-based electrodes under saturated glucose conditions. For the cathodic reaction, the MWCNT-based cathode performs marginally better than the CMK-3-based electrodes in the presence of bilirubin oxidase (BOD) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS2−). The CMK-3-based EFCs assembled from the GOx anode and BOD cathode results in a power output of 93 μW cm−2. In contrast, the output power of MWCNT-based EFCs is approximately 53 μW cm−2. The efficiency of CMK-3 as a support material for biofuel cell applications is effectively demonstrated.

Microbial Biofuel Cells: Fundamental Principles, Development and Recent Obstacles.

This review focuses on the development of microbial biofuel cells to demonstrate how similar principles apply to the development of bioelectronic devices. The low specificity of microorganism-based amperometric biosensors can be exploited in designing microbial biofuel cells, enabling them to consume a broader range of chemical fuels. Charge transfer efficiency is among the most challenging and critical issues while developing biofuel cells. Nanomaterials and particular redox mediators are exploited to facilitate charge transfer between biomaterials and biofuel cell electrodes. The application of conductive polymers (CPs) can improve the efficiency of biofuel cells while CPs are well-suitable for the immobilization of enzymes, and in some specific circumstances, CPs can facilitate charge transfer. Moreover, biocompatibility is an important issue during the development of implantable biofuel cells. Therefore, biocompatibility-related aspects of conducting polymers with microorganisms are discussed in this review. Ways to modify cell-wall/membrane and to improve charge transfer efficiency and suitability for biofuel cell design are outlined.

Metal Organic Frameworks for Bioelectrochemical Applications

AbstractMetal organic frameworks (MOFs) with their high pore volumes and chemically‐diverse pore environments have emerged as components of catalytic electrodes for biosensors, biofuel cells, and bioreactors. MOFs are widely exploited for gas capture, separations, and catalysis, but their integration at electrodes with biocatalysts for (bio)electrocatalysis is a niche topic that remains largely unexplored. This review focuses on recent advances in MOF and MOF‐derived carbon electrodes for bioelectrochemical applications. A range of MOF materials and their integration into devices with enzymes and microbes are reported. Key properties and performance characteristics are considered and opportunities facing MOFs for (bio)electrochemical applications are discussed.

Nanocellulose Paper Semiconductor with a 3D Network Structure and Its Nano-Micro-Macro Trans-Scale Design.

Semiconducting nanomaterials with 3D network structures exhibit various fascinating properties such as electrical conduction, high permeability, and large surface areas, which are beneficial for adsorption, separation, and sensing applications. However, research on these materials is substantially restricted by the limited trans-scalability of their structural design and tunability of electrical conductivity. To overcome this challenge, a pyrolyzed cellulose nanofiber paper (CNP) semiconductor with a 3D network structure is proposed. Its nano–micro–macro trans-scale structural design is achieved by a combination of iodine-mediated morphology-retaining pyrolysis with spatially controlled drying of a cellulose nanofiber dispersion and paper-crafting techniques, such as microembossing, origami, and kirigami. The electrical conduction of this semiconductor is widely and systematically tuned, via the temperature-controlled progressive pyrolysis of CNP, from insulating (1012 Ω cm) to quasimetallic (10–2 Ω cm), which considerably exceeds that attained in other previously reported nanomaterials with 3D networks. The pyrolyzed CNP semiconductor provides not only the tailorable functionality for applications ranging from water-vapor-selective sensors to enzymatic biofuel cell electrodes but also the designability of macroscopic device configurations for stretchable and wearable applications. This study provides a pathway to realize structurally and functionally designable semiconducting nanomaterials and all-nanocellulose semiconducting technology for diverse electronics.

In vivo electrochemically-assisted polymerization of conjugated functionalized terthiophenes inside the vascular system of a plant

We investigate the possibility of producing biofuel cell electrode materials in vivo by injecting the reagents directly into plant tissues. We first introduce model electroactive substances Fe(CN)64− and Ru(NH3)63+ into a Nicotiana tabacum leaf. In situ electrochemical measurements make it possible to trace the distribution of these substances. As well as mapping the vascular content, electrochemistry can be used to trigger reactions directly inside the plant. The injection of thiophene (T) and ethylenedioxythiophene (E)-based trimers (ETE) anchoring an Os(2,2′-bipyridine)2(1-(3-aminopropyl)-imidazole)Cl Os-complex followed by the application of anodic polarization triggers a polymerization reaction in the region of the plant vascular system containing the monomer, showing that it is possible to generate electroactive organic macromolecules locally in vivo.

Superior performance of a graphdiyne self-powered biosensor with exonuclease III-assisted signal amplification for sensitive detection of microRNAs.

Graphdiyne (GDY) is an sp and sp2 co-hydrocarbon allotrope whose particular structure endows it with many fascinating properties, including abundant chemical bonds, high conjugation, natural pores, high carrier mobility, high conductivity and stability, etc. In this work, two-dimensional graphdiyne is prepared as an electrode substrate material coupling with an exonuclease III-assisted amplification strategy to construct a superior-performance self-powered biosensor based on enzymatic biofuel cells for highly sensitive detection of the tumour marker miRNA-21. Glucose oxidase (GOD) is first immobilized on the GDY/AuNP composite to prepare a bioconjugate. GDY/AuNP modified carbon cloth is used as an enzyme biofuel cell electrode, which is then modified with bilirubin oxidase as a biocathode. The bioconjugate binds to GOD through specific binding to the bioanode. When miRNA-21 is present, specific recognition by exonuclease III in the system results in cleavage of the capture probe, and miRNA-21 is recovered and involved in the cycle. The target miRNA-21 then causes corresponding changes in the open-circuit voltage of the self-powered system. Based on this, a sensitive detection method was constructed, within the scope from 0.1 fM to 0.1 nM with a shallow detection limit of 55.2 aM (S/N = 3). The new approach triumphantly has been used to detect miRNA-21 in serum, which provides a compelling new way for early diagnosis of related cancers.

Self-Powered Diaper Sensor with Wireless Transmitter Powered by Paper-Based Biofuel Cell with Urine Glucose as Fuel.

A self-driven sensor that can detect urine and urine sugar and can be mounted on diapers is desirable to reduce the burden of long-term care. In this study, we created a paper-based glucose biofuel cell that can be mounted on diapers to detect urine sugar. Electrodes for biofuel cells were produced by printing MgO-templated porous carbon on which poly(glycidyl methacrylate) was modified using graft polymerization. A new bioanode was prepared through covalently modifying flavin-adenine-dinucleotide-dependent glucose dehydrogenase and azure A with pendant glycidyl groups of poly(glycidyl methacrylate). We prepared a cathode with covalently bonded bilirubin oxidase. Covalent bonding of enzymes and mediators to both the bioanode and biocathode suppressed elution and improved stability. The biofuel cell could achieve a maximum output density of 0.12 mW cm–2, and by combining it with a wireless transmission device, the concentration of glucose sensed from the transmission frequency was in the range of 0–10 mM. The sensitivity of the sensor was estimated at 0.0030 ± 0.0002 Hz mmol–1 dm3. This device is expected to be a new urine-sugar detection device, composed only of organic materials with a low environmental load and it can be useful for detecting postprandial hyperglycemia.

Effect of electrochemical functionalization of single-walled carbon nanotube electrodes in flexible enzymatic biofuel cells

We report a flexible enzymatic biofuel cell based on electrochemically functionalized single-walled carbon nanotube (SWNT) electrodes. Comparative studies on the impact of the electrochemical functionalization of the SWNT electrodes on the device performance revealed a 40%–110% increase in power density as compared to that of the device with as-fabricated SWNT electrodes, with an observed maximum power density of 7.2 μW cm−2. This improvement in performance can be attributed to the increase in the amount of enzymes adsorbed on the SWNT surface and the enhanced electron transfer rate owing to the SWNT functionalization. Our findings can aid improve the performance of flexible and high-power-density biofuel cells.

Engineering the Turnover Stability of Cellobiose Dehydrogenase toward Long-Term Bioelectronic Applications.

Cellobiose dehydrogenase (CDH) is an attractive oxidoreductase for bioelectrochemical applications. Its two-domain structure allows the flavoheme enzyme to establish direct electron transfer to biosensor and biofuel cell electrodes. Yet, the application of CDH in these devices is impeded by its limited stability under turnover conditions. In this work, we aimed to improve the turnover stability of CDH by semirational, high-throughput enzyme engineering. We screened 13 736 colonies in a 96-well plate setup for improved turnover stability and selected 11 improved variants. Measures were taken to increase the reproducibility and robustness of the screening setup, and the statistical evaluation demonstrates the validity of the procedure. The selected CDH variants were expressed in shaking flasks and characterized in detail by biochemical and electrochemical methods. Two mechanisms contributing to turnover stability were found: (i) replacement of methionine side chains prone to oxidative damage and (ii) the reduction of oxygen reactivity achieved by an improved balance of the individual reaction rates in the two CDH domains. The engineered CDH variants hold promise for the application in continuous biosensors or biofuel cells, while the deduced mechanistic insights serve as a basis for future enzyme engineering approaches addressing the turnover stability of oxidoreductases in general.

From Microorganism-Based Amperometric Biosensors towards Microbial Fuel Cells.

This review focuses on the overview of microbial amperometric biosensors and microbial biofuel cells (MFC) and shows how very similar principles are applied for the design of both types of these bioelectronics-based devices. Most microorganism-based amperometric biosensors show poor specificity, but this drawback can be exploited in the design of microbial biofuel cells because this enables them to consume wider range of chemical fuels. The efficiency of the charge transfer is among the most challenging and critical issues during the development of any kind of biofuel cell. In most cases, particular redox mediators and nanomaterials are applied for the facilitation of charge transfer from applied biomaterials towards biofuel cell electrodes. Some improvements in charge transfer efficiency can be achieved by the application of conducting polymers (CPs), which can be used for the immobilization of enzymes and in some particular cases even for the facilitation of charge transfer. In this review, charge transfer pathways and mechanisms, which are suitable for the design of biosensors and in biofuel cells, are discussed. Modification methods of the cell-wall/membrane by conducting polymers in order to enhance charge transfer efficiency of microorganisms, which can be potentially applied in the design of microbial biofuel cells, are outlined. The biocompatibility-related aspects of conducting polymers with microorganisms are summarized.

Exploring the shape and distribution of electrodes in membraneless enzymatic biofuel cells for high power output

Enzymatic biofuel cells (EBFCs) have great application prospects by catalyzing the redox reaction of biofuels to generate electricity. In order to further improve the output performance of EBFCs, the influences of electrode shape and array on the outputs of EBFCs were investigated by finite element analysis. The relationship between electrode shapes and the distribution of field strength and voltage were firstly explored by graphical method. According to simulation results, circular electrodes distribution would be the best choice for EBFCs with a maximum power density (MPD) of over 4.7 mW cm−2 and the least current density range of 4.4 mA cm−2 under ideal conditions. The hexagonal close-packed array was able to distribute more electrodes and thus obtain higher total power outputs. For the monopolar plate EBFCs, anodes and cathodes were interlaced on the same plate to facilitate the application of wearable and implantable devices. Moreover, the network topology theory was applied to the design of electrode array in EBFCs, which provided extensive electrode array structures for EBFCs. The results exhibited that the MPD of radial and star topologies were both about 4.7 mW cm−2, while that of ring topology was much smaller. The electrode shape and electrode array studied in this paper would be of great significance to the structural design of EBFCs devices.

Enzyme-modified electrodes for biofuel cells: A comprehensive review

Enzyme centered biofuel cells became the center of focus for various researchers recently owing to their wide spread applications on several fields. During the current times, experimental research has been widely conducted in applications like biosensor and biofuel cell that contains enzyme electrodes. The interest in developing enzyme modified electrodes for biofuel cells increases rapidly because of the flourishment of healthcare applications that utilizes more number of medical devices for implantation. This review considers the literature on enzymatic electrodes for biofuel cells. Normally nano-carbons are used for manufacturing of enzyme-modified electrodes for biofuel cells owing to their large specific surface area. The stability of these enzyme-modified bio-electrodes becomes an significant parameter in measuring the biofuel cell life time.

In situ growth of hybrid nanoflowers on activated carbon fibers as electrodes for mediatorless enzymatic biofuel cells

Hybrid nanoflowers (HnFs) are novel structures that comprise enzymes (laccase, glucose oxidase, or catalase) and Cu3(PO4)2-based crystals, which can directly in situ grow on activated carbon fibers (ACFs) for the preparation of electrodes (HnF/ACF) used in glucose biofuel cells. The HnF/ACF structures perform higher enzymatic activities (~4 times) and stability (~2 times) than the enzymes physically adsorbed on ACFs in distinct analyses such as epinephrine oxidation, H2O2 decomposition, and glucose oxidation. The power density of an HnF/ACF-based cell (50 µW cm−2 for a glucose concentration of 50 mM) is 3–5 times higher than that of a cell prepared from conventional enzyme immobilization routes, which can be sustained at up to 80% after one month of operation.

Autonomous Energy Harvester Based on Textile-Based Enzymatic Biofuel Cell for On-Demand Usage.

This paper presents an autonomous energy harvester based on a textile-based enzymatic biofuel cell, enabling an efficient power management and on-demand usage. The proposed biofuel cell works by an enzymatic reaction with glucose in sweat absorbed by the specially designed textile for sustainable and efficient energy harvesting. The output power of the textile-based biofuel cell has been optimized by changing electrode size and stacking electrodes and corresponding fluidic channels suitable for following power management circuit. The output power level of single electrode is estimated less than 0.5 μW and thus a two-staged power management circuit using intermediate supercapacitor has been presented. As a solution to produce a higher power level, multiple stacks of biofuel cell electrodes have been proposed and thus the textile-based biofuel cell employing serially connected 5 stacks produces a maximal power of 13 μW with an output voltage of 0.88 V when load resistance is 40 kΩ. A buck-boost converter employing a crystal oscillator directly triggered by DC output voltage of the biofuel cell makes it possible to obtain output voltage of the DC–DC converter is 6.75 V. The efficiency of the DC–DC converter is estimated as approximately 50% when the output power of the biofuel cell is tens microwatts. In addition, LT-spice modeling and simulation has been presented to estimate power consumption of each element of the proposed DC–DC converter circuit and the predicted output voltage has good agreement with measurement result.

Membraneless enzymatic biofuel cells using iron and cobalt co-doped ordered mesoporous porphyrinic carbon based catalyst

Iron and cobalt co-doped ordered mesoporous porphyrinic carbon (FeCo-OMPC) is employed as the catalyst for both electrodes in membraneless enzymatic biofuel cells (EBCs). FeCo-OMPC is used for catalyzing oxygen redox reaction (ORR), while GOx/[FeCo-OMPC/CNT] is utilized as a catalyst for a series of glucose oxidation reaction (GOR) and hydrogen peroxide oxidation reaction (HPOR). The onset potential of the ORR by FeCo-OMPC is 0.31 V vs. Ag/AgCl, while that of HPOR by FeCo-OMPC/CNT and GOR-HPOR by GOx/[FeCo-OMPC/CNT] are both 0.12 V. The activity of this catalyst is better than previously reported similar catalysts due to the presence of Co species and high metal contents. As a result, the concentration of H2O2 generated by GOR is 1.02–1.56 mM when the same glucose concentration as human blood is used. In addition, the EBC using GOx/[FeCo-OMPC/CNT] and FeCO-OMPC shows the maximum power density of 21.3 ± 2.97 μW cm−2 with open circuit voltage (OCV) of 0.17 ± 0.016 V. These values are significantly higher than those of EBC using the competitive Fe–N/CNT catalyst (0.11 V and 9.6 μW cm−2). Moreover, the OCV is close to the expected value by CV (0.19 V), confirming that the FeCo-OMPC catalyst can be used for implantable bioelectronics, such as biosensors and electroceuticals.

Ternary graphene@polyaniline-TiO2 composite for glucose biofuel cell anode application

In this work p-toluenesulfonic acid (p-TSA) doped highly conductive ternary graphene @polyaniline-TiO2 (GN@Pani-TiO2) was synthesized chemically. The conducting polymers incorporated with metal oxide have good electrical conductivity and large pseudo capacitance which have been utilized as a potential electrode material for biofuel cell electrode preparation. The redox mediator ferritin (Frt) and enzyme glucose oxidase (GOx) was immobilized successfully. The oxidation of glucose by the prepared bioanode was increased with the increase in glucose concentration in the range of 4–24 mM. The electrochemical performance of the bioanode was satisfactory at 20 mM glucose in a phosphate buffer solution (PBS) of pH 7.0 analyzed by cyclic voltammetry (CV) in 20 mM of glucose at different scan rates (20–100 mVs−1), linear sweep voltammetry (LSV) and chronoamperometry. A saturation current density of 6.77 ± 0.2 mAcm−2 was achieved at a 100 mVs−1 scan rate for 20 mM of glucose oxidation.

Fabrication of optimally configured layers of SWCNTs, gold nanoparticles, and glucose oxidase on ITO electrodes for high-power enzymatic biofuel cells

We designed an enzymatic biofuel cell (EFC) that utilizes indium tin oxide (ITO) electrodes, and sequential deposition of single-walled carbon nanotube (SWCNT) and gold nanoparticle (AuNP) layers on the electrodes to enhance their electron transfer. Cyclic voltammograms of the SWCNT-modified ITO electrodes showed higher peak currents compared to those of the bare ITO electrodes. Immobilization of glucose oxidase (GOD) on SWCNT-modi-fied ITO electrodes increased their electron transfer resistance by a factor of ten, which could be mitigated by incorporating an AuNP layer between the GOD and SWCNT layers. The single-layer GOD generated higher current than the doubled-layer GOD, with higher specific activity. The assembled EFC featured SWCNT-modified ITO electrodes with sequential layers of immobilized AuNPs and GOD (anode), and with a single layer of immobilized bilirubin oxidase (BOD) (cathode). The cathode performance was further improved by the presence of AuNPs between the BOD and SWCNTs on cathode. The enhanced electron transfer kinetics and enzymatic activity observed for SWCNT/AuNP-modified ITO electrodes resulted in a maximum power density of 38.2±2.0 µW/cm2 at 0.57±0.03 V of a cell voltage.

Effect of Surface and Bulk Properties of Mesoporous Carbons on the Electrochemical Behavior of GOx-Nanocomposites

Biofuel cell (BFC) electrodes are typically manufactured by combining enzymes that act as catalysts with conductive carbon nanomaterials in a form of enzyme-nanocomposite. However, a little attention has been paid to effects of the carbon nanomaterials' structural properties on the electrochemical performances of the enzyme-nanocomposites. This work aims at studying the effects of surface and bulk properties of carbon nanomaterials with different degrees of graphitization on the electrochemical performances of glucose oxidase (GOx)-nanocomposites produced by immobilizing GOx within a network of carbon nanopaticles. Two types of carbon nanomaterials were used: graphitized mesoporous carbon (GMC) and purified mesoporous carbon (PMC). Graphitization index, surface functional groups, hydrophobic properties, and rate of aggregation were measured for as-received and acid-treated GMC and PMC samples by using Raman spectrometry, X-ray photoelectron spectroscopy (XPS), contact angle measurement, and dynamic light scattering (DLS), respectively. In addition to these physical property characterizations, the enzyme loading and electrochemical performances of the GOx-nanocomposites were studied via elemental analysis and cyclic voltammetry tests, respectively. We also fabricated BFCs using our GOx-nanocomposite materials as the enzyme anodes, and tested their performances by obtaining current-voltage (IV) plots. Our findings suggest that the electrochemical performance of GOx-nanocomposite material is determined by the combined effects of graphitization index, electrical conductivity and surface chemistry of carbon nanomaterials.