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An enzyme‐based biofuel cell (EBFC) is widely regarded as one of the most efficient power sources for bio‐friendly and implantable medical devices, capable of converting electrochemical reactions into electrical currents under physiological conditions. However, despite its potential, the practical and commercial use of EBFCs is limited by their low power output and operational instability. Therefore, significant research efforts have focused on increasing power output and stability by improving electron transfer between enzymes and host electrodes and developing efficient enzyme immobilization techniques. However, most EBFCs produced by current methods still deliver unsatisfactory performance. A promising approach to address these challenges is the use of conductive linkers that promote favorable interfacial interactions between adjacent enzymes and between enzymes and host electrodes. These linkers can facilitate electron transfer and ensure robust enzyme immobilization. In addition, designing the host electrode with a 3D structure and a large surface area can further improve the areal energy performance. This perspective reviews the working principles, types, and electron transfer mechanisms of EBFC electrodes and explores how conductive linkers and 3D host electrodes can enhance the performance of EBFC electrodes. Finally, recent advances in integrating EBFCs into biomedical devices are described. [ABSTRACT FROM AUTHOR]

Biofuel cells (BFCs) offer an eco‐friendly route to convert biochemical energy into electricity. However, their performance is hindered by insufficient enzyme immobilization as well as limited electron transfer within the enzymatic electrode. While the incorporation of redox mediators (RMs) into enzyme layers has been shown to improve BFC performance through enhanced electron transfer, progress has plateaued in the last decade. Herein, a major breakthrough is presented realized by a novel strategy that exploits electron transfer‐intensified RM layers. Metal nanoparticles covalently bridged between neighboring RMs facilitate electron transfer ubiquitously. Electron transfer characteristics are enhanced not only within the RM layers themselves, but also at the glucose oxidase (GOx)/host electrode and GOx/GOx interfaces. This leads to a remarkable performance boost in the enzymatic anode. A hybrid BFC constructed with innovative anode and Pt‐based cathode exhibits a striking combination of high power output (2.3 and 8.5 mW cm−2 at 10 and 300 mmol L−1 glucose, respectively) and exceptional operational stability (≈80% and 47% power retention after 10 days and 1 month, respectively), outperforming all previously reported BFCs by a significant margin. [ABSTRACT FROM AUTHOR]

Carbon‐based nanozymes have received considerable attention due to their superior biosafety, enhanced tolerance to extreme conditions, and ease of chemical modification. However, due to limited material diversity and unconfirmed molecular structure, carbon‐based nanozymes face challenges such as relatively low enzyme activity and unclear catalytic mechanisms. The development of materials with well‐defined structures and controllable properties is crucial for promoting the rapid progress of nanozymes. Herein, 3,4,9,10‐perylenetetracarboxylic dianhydride (PD) exhibits both glucose oxidase (GOx)‐like and catalase (CAT)‐like activities, which may be due to the fact that PD possesses the features of highly conjugated structure and high electron mobility. In addition, it is demonstrated that the enzymatic activity is related to the degree of PD aggregation via the characterization of its morphology and size. Based on the excellent GOx‐like and CAT‐like activities of PD, a self‐cascade catalytic system is constructed for application in biofuel cells (BFCs). It is worth mentioning that such BFC still maintains high stability after working for 30 days. Therefore, this study expands the enzyme‐like systems and discovers that nanomaterials with highly conjugated structures and high electron mobility can mimic enzymes. Additionally, the multi‐enzyme activities are utilized to construct self‐cascade systems, which can effectively improve the performance of BFCs. [ABSTRACT FROM AUTHOR]

A novel biofuel cell (BFC)-based self-powered electrochemical immunosensing platform was developed by integrating the target-induced biofuel release and biogate immunoassay for ultrasensitive 17β-estradiol (E2) detection. The carbon nanocages/gold nanoparticle composite was employed in the BFCs device as the electrode material, through which bilirubin oxidase and glucose oxidase were wired to form the biocathode and bioanode, respectively. Positively charged mesoporous silica nanoparticles (PMSN) were encapsulated with glucose molecules as biofuel and subsequently coated by the negatively charged AuNPs-labelled anti-E2 antibody (AuNPs-Ab) serving as a biogate. The biogate could be opened efficiently and the trapped glucose released once the target E2 was recognized and captured by AuNPs-Ab due to the decreased adhesion between the antigen–antibody complex and PMSN. Then, glucose oxidase oxidized the glucose to produce a large number of electrons, resulting in significantly increased open-circuit voltage (EOCV). Promisingly, the proposed BFC-based self-powered immunosensor demonstrated exceptional sensitivity for the detection of E2 in the concentration range from 1.0 pg mL−1 to 10.0 ng mL −1, with a detection limit of 0.32 pg mL−1 (S/N = 3). Furthermore, the prepared BFC-based self-powered homogeneous immunosensor showed significant potential for implementation as a viable prototype for a mobile and an on-site bioassay system in food and environmental safety applications. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are sustainable energy recovery systems because they use organic waste as biofuel. Using critical raw materials (CRMs), like platinum-group metals, at the cathode side threatens MFC technology's sustainability and raises costs. By developing an efficient electrode design for MFC performance enhancement, CRM-based cathodic catalysts should be replaced with CRM-free materials. This work proposes developing and optimizing iron-based air cathodes for enhancing oxygen reduction in MFCs. By subjecting iron phthalocyanine and carbon black pearls to controlled thermal treatments, we obtained Fe-based electrocatalysts combining high surface area (628 m2 g−1) and catalytic activity for O2 reduction at near-neutral pH. The electrocatalysts were integrated on carbon cloth and carbon paper to obtain gas diffusion electrodes whose architecture was optimized to maximize MFC performance. Excellent cell performance was achieved with the carbon-paper-based cathode modified with the Fe-based electrocatalysts (maximum power density-PDmax = 1028 mWm−2) compared to a traditional electrode design based on carbon cloth (619 mWm−2), indicating the optimized cathodes as promising electrodes for energy recovery in an MFC application. [ABSTRACT FROM AUTHOR]

Environmental pollution is becoming ubiquitous; it has a negative impact on ecosystem diversity and worsens the quality of human life. This review discusses the possibility of applying the plant microbial fuel cells (PMFCs) technology for concurrent processes of electricity generation and the purification of water and soil ecosystems from organic pollutants, particularly from synthetic surfactants and heavy metals. The review describes PMFCs' functioning mechanisms and highlights the issues of PMFCs' environmental application. Generally, this work summarizes different approaches to PMFC development and to the potential usage of such hybrid bioelectrochemical systems for environmental protection. [ABSTRACT FROM AUTHOR]

Various sensors and electronic devices are recently developed to monitor human health in mechanically flexible or even stretchable forms for intimate contact with non‐flat curvilinear surfaces of the human body. For successful operation of these devices, finding a proper way to electrically power them is very important. In this work, glucose/oxygen fueled enzymatic biofuel cells (EBFCs) based on microfluidic structured elastomeric polydimethylsiloxane substrate with wrinkled gold (Au) electrodes are suggested for power supply. For doing that, firstly, bottom surface of microfluidic channel is covered with buckled Au electrodes for stretchability. By microfluidic design showing capillary imbibition through fluidic channels, loading of catalyts is promoted. Interestingly, buckled Au electrodes induce much better anodic and cathodic reaction rates than those of non‐buckled Au electrodes by 25% and 33%, respectively. This is because surface area and the amount of catalyst loading in electrodes increase by Au wrinkling. In evaluations of EBFCs using the buckled Au electrodes, maximum power density reaches 7.1 ± 0.64 µW cm−2, while they show decent performance of 5.4 ± 0.49 µW cm−2 even under external stretching. Taken together, it is corroborated that such proposed stretchable EBFCs are alternative for providing electrical power in wearable or implantable devices. [ABSTRACT FROM AUTHOR]

Quick and effective point-of-care (POC) devices have the chance to revolutionize healthcare in developed and developing countries since they can operate anywhere the patient is, with the possibility of obtaining and sending the results to the doctor without delay. In recent years, significant efforts have focused on developing new POC systems that can screen for biomarkers continuously and non-invasively in body fluids to prevent, diagnose, and manage diseases. However, one of the critical challenges left to address is how to power them effectively and sufficiently. In developing countries and rural and remote areas, where there are usually no well-established electricity grids or nearby medical facilities, and using batteries is unreliable or not cost-effective, alternative power sources are the most challenging issue for stand-alone and self-sustained POC devices. Here, we provide an overview of the techniques for used self-powering POC devices, where the sample is used to detect and simultaneously generate energy to power the system. Likewise, this paper introduced the state-of-the-art with a review of different research projects, patents, and commercial products for self-powered POCs from the mid-2010s until present day. [ABSTRACT FROM AUTHOR]

Chemical biomarkers in the central nervous system can provide valuable quantitative measures to gain insight into the etiology and pathogenesis of neurological diseases. Glutamate, one of the most important excitatory neurotransmitters in the brain, has been found to be upregulated in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, stroke, epilepsy, chronic pain, and migraines. However, quantitatively monitoring glutamate release in situ has been challenging. This work presents a novel class of flexible, miniaturized probes inspired by biofuel cells for monitoring synaptically released glutamate in the nervous system. The resulting sensors, with dimensions as low as 50 by 50 μm, can detect real‐time changes in glutamate within the biologically relevant concentration range. Experiments exploiting the hippocampal circuit in mice models demonstrate the capability of the sensors in monitoring glutamate release via electrical stimulation using acute brain slices. These advances could aid in basic neuroscience studies and translational engineering, as the sensors provide a diagnostic tool for neurological disorders. Additionally, adapting the biofuel cell design to other neurotransmitters can potentially enable the detailed study of the effect of neurotransmitter dysregulation on neuronal cell signaling pathways and revolutionize neuroscience. [ABSTRACT FROM AUTHOR]

Chemical biomarkers in the central nervous system can provide valuable quantitative measures to gain insight into the etiology and pathogenesis of neurological diseases. Glutamate, one of the most important excitatory neurotransmitters in the brain, has been found to be upregulated in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, stroke, epilepsy, chronic pain, and migraines. However, quantitatively monitoring glutamate release in situ has been challenging. This work presents a novel class of flexible, miniaturized probes inspired by biofuel cells for monitoring synaptically released glutamate in the nervous system. The resulting sensors, with dimensions as low as 50 by 50 μm, can detect real‐time changes in glutamate within the biologically relevant concentration range. Experiments exploiting the hippocampal circuit in mice models demonstrate the capability of the sensors in monitoring glutamate release via electrical stimulation using acute brain slices. These advances could aid in basic neuroscience studies and translational engineering, as the sensors provide a diagnostic tool for neurological disorders. Additionally, adapting the biofuel cell design to other neurotransmitters can potentially enable the detailed study of the effect of neurotransmitter dysregulation on neuronal cell signaling pathways and revolutionize neuroscience. [ABSTRACT FROM AUTHOR]

The extraordinary potential of hydrogen as a clean and sustainable fuel has sparked the interest of the scientific community to find environmentally friendly methods for its production. Biological catalysts are the most attractive solution, as they usually operate under mild conditions and do not produce carbon-containing byproducts. Hydrogenases promote reversible proton reduction to hydrogen in a variety of anoxic bacteria and algae, displaying unparallel catalytic performances. Attempts to use these sophisticated enzymes in scalable hydrogen production have been hampered by limitations associated with their production and stability. Inspired by nature, significant efforts have been made in the development of artificial systems able to promote the hydrogen evolution reaction, via either electrochemical or light-driven catalysis. Starting from small-molecule coordination compounds, peptide- and protein-based architectures have been constructed around the catalytic center with the aim of reproducing hydrogenase function into robust, efficient, and cost-effective catalysts. In this review, we first provide an overview of the structural and functional properties of hydrogenases, along with their integration in devices for hydrogen and energy production. Then, we describe the most recent advances in the development of homogeneous hydrogen evolution catalysts envisioned to mimic hydrogenases. [ABSTRACT FROM AUTHOR]

Highlights: Screen-printable functional nanocomposite inks are engineered for flexible, single-enzyme-based energy-harvesting, and self-powered biosensing devices. A BFC powered by the same biosubstrate (glucose) is developed to harvest energy in a biofluid model and act as a self-powered electrochemical glucose. Customized inks are advantageous in terms of integrating with flexible materials, which can be integrated with a wide range of wearables and soft bioelectronics. Developing flexible bioelectronics is essential to the realization of artificial intelligence devices and biomedical applications, such as wearables, but their potential is limited by sustainable energy supply. An enzymatic biofuel cell (BFC) is promising for power supply, but its use is limited by the challenges of incorporating multiple enzymes and rigid platforms. This paper shows the first example of screen-printable nanocomposite inks engineered for a single-enzyme-based energy-harvesting device and a self-powered biosensor driven by glucose on bioanode and biocathode. The anode ink is modified with naphthoquinone and multiwalled carbon nanotubes (MWCNTs), whereas the cathode ink is modified with Prussian blue/MWCNT hybrid before immobilizing with glucose oxidase. The flexible bioanode and the biocathode consume glucose. This BFC yields an open circuit voltage of 0.45 V and a maximum power density of 266 μW cm−2. The wearable device coupled with a wireless portable system can convert chemical energy into electric energy and detect glucose in artificial sweat. The self-powered sensor can detect glucose concentrations up to 10 mM. Common interfering substances, including lactate, uric acid, ascorbic acid, and creatinine, have no effect on this self-powered biosensor. Additionally, the device can endure multiple mechanical deformations. New advances in ink development and flexible platforms enable a wide range of applications, including on-body electronics, self-sustainable applications, and smart fabrics. [ABSTRACT FROM AUTHOR]

Glucose oxidase (GOx)-based electrodes are important for bioelectronics, such as glucose sensors. It is challenging to effectively link GOx with nanomaterial-modified electrodes while preserving enzyme activity in a biocompatible environment. To date, no reports have used biocompatible food-based materials, such as egg white proteins, combined with GOx, redox molecules, and nanoparticles to create the biorecognition layer for biosensors and biofuel cells. This article demonstrates the interface of GOx integrated with egg white proteins on a 5 nm gold nanoparticle (AuNP) functionalized with a 1,4-naphthoquinone (NQ) and conjugated with a screen-printed flexible conductive carbon nanotube (CNT)-modified electrode. Egg white proteins containing ovalbumin can form three-dimensional scaffolds to accommodate immobilized enzymes and adjust the analytical performance. The structure of this biointerface prevents the escape of enzymes and provides a suitable microenvironment for the effective reaction. The bioelectrode's performance and kinetics were evaluated. Using redox-mediated molecules with the AuNPs and the three-dimensional matrix made of egg white proteins improves the transfer of electrons between the electrode and the redox center. By engineering the layer of egg white proteins on the GOx-NQ-AuNPs-mediated CNT-functionalized electrodes, we can modulate analytical performances such as sensitivity and linear range. The bioelectrodes demonstrate high sensitivity and can prolong the stability by more than 85% after 6 h of continuous operation. The use of food-based proteins with redox molecule-modified AuNPs and printed electrodes demonstrates advantages for biosensors and energy devices due to their small size, large surface area, and ease of modification. This concept holds a promise for creating biocompatible electrodes for biosensors and self-sustaining energy devices. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are crystalline materials that are formed by self-assembling organic linkers and metal ions with large specific areas and pore volumes. Their chemical tunability, structural diversity, and tailor-ability make them adaptive to decorate many substrate materials, such as biomass-derived carbon materials, and competitive in many environmental biosystems, such as biofuel cells, bioelectrocatalysts, microbial metal reduction, and fermentation systems. In this review, we surmised the recent progress of MOFs and MOF-derived materials and their applications in environmental biosystems. The behavior of MOFs and MOF-derived materials in different environmental biosystems and their influences on performance are described. The inherent mechanisms will guide the rational design of MOF-related materials and lead to a better understanding of their interaction with biocomponents. [ABSTRACT FROM AUTHOR]

Metal 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. [ABSTRACT FROM AUTHOR]

An efficient immobilization of Glucose oxidase (GOx) on an appropriate substrate is one of the main challenges of developing fuel cells that allow energy to be obtained from renewable substrates such as carbohydrates in physiological environments. The research importance of biofuel cells relies on their experimental robustness and high compatibility with biological organisms such as tissues or the bloodstream with the aim of obtaining electrical energy even from living systems. In this work, we report the use of 5,10,15,20 tetrakis (1-methyl-4-pyridinium) porphyrin and glutathione capped CdTe Quantum dots (GSH-CdTeQD) as a support matrix for the immobilization of GOx on carbon surfaces. Fluorescent GSH-CdTeQD particles were synthesized and their characterization by UV-Vis spectrophotometry showed a particle size between 5–7 nm, which was confirmed by DLS and TEM measurements. Graphite and Toray paper electrodes were modified by a drop coating of porphyrin, GSH-CdTeQD and GOx, and their electrochemical activity toward glucose oxidation was evaluated by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Additionally, GOx modified electrode activity was explored by scanning electrochemical microscopy, finding that near to 70% of the surface was covered with active enzyme. The modified electrodes showed a glucose sensitivity of 0.58 ± 0.01 μA/mM and an apparent Michaelis constant of 7.8 mM. The addition of BSA blocking protein maintained the current response of common interferent molecules such as ascorbic acid (AA) with less than a 5% of interference percentage. Finally, the complex electrodes were employed as anodes in a microfluidic biofuel cell (μBFC) in order to evaluate the performance in energy production. The enzymatic anodes used in the μBFC allowed us to obtain a current density of 7.53 mAcm−2 at the maximum power density of 2.30 mWcm−2; an open circuit potential of 0.57 V was observed in the biofuel cell. The results obtained suggest that the support matrix porphyrin and GSH-CdTeQD is appropriate to immobilize GOx while preserving the enzyme's catalytic activity. The reported electrode arrangement is a viable option for bioenergy production and/or glucose quantification. [ABSTRACT FROM AUTHOR]

Wearable biofuel cells (BFCs) technologies have the potential to address the challenge of on‐body energy supply of wearable electronics. However, previous wearable BFCs primarily focus on "worn‐on‐skin" sweat ones, which can hardly directly generate steady and nonintermittent electricity under certain but almost ineluctable wearable circumstances (e.g., intermittent sweating, perspiration biofuel concentration fluctuation, and dynamic contact between wearable BFCs and epidermal sweat). Here, in an alternative "worn‐close to‐skin" manner, the first example of a flexible BFC‐in‐a‐tube (named iezTube) as an entirely self‐contained wearable BFC (ESW‐BFC) for wearable energy generation by integrating a single‐layer fluff pulp (FP)‐based microfluidic module for the efficient sampling/utilization of biofuel fluids and the steady contact between biofuel fluids and wearable BFC with a flexible nano‐engineered BFC‐based BFC module for real‐time bio‐energy generation, along with an air‐breathing module that is based on a breathable and waterproof non‐woven tapes covered centrifuge tube‐based for continuous oxidizer supply, is reported. Through the seamless system integration, effective series‐connection pattern, and diverse readily accessible biofuel fluids pre‐collection, the iezTube demonstrates an exceptional capability to steadily and nonintermittently power wearable electronics under some certain but nearly ineluctable wearable circumstances and holds considerable and inimitable prospects as an ESW‐BFC for wearable electronics. [ABSTRACT FROM AUTHOR]

Many healthcare and environmental monitoring devices use electrochemical techniques to detect and quantify analytes. With sensors progressively becoming smaller—particularly in point‐of‐care (POC) devices and wearable platforms—it creates the opportunity to operate them using less energy than their predecessors. In fact, they may require so little power that can be extracted from the analyzed fluids themselves, for example, blood or sweat in case of physiological sensors and sources like river water in the case of environmental monitoring. Self‐powered electrochemical sensors (SPES) can generate a response by utilizing the available chemical species in the analyzed liquid sample. Though SPESs generate relatively low power, capable devices can be engineered by combining suitable reactions, miniaturized cell designs, and effective sensing approaches for deciphering analyte information. This review details various such sensing and engineering approaches adopted in different categories of SPES systems that solely use the power available in liquid sample for their operation. Specifically, the categories discussed in this review cover enzyme‐based systems, battery‐based systems, and ion‐selective electrode‐based systems. The review details the benefits and drawbacks with these approaches, as well as prospects of and challenges to accomplishing them. [ABSTRACT FROM AUTHOR]

Effective wound management has the potential to reduce both the duration and cost of wound healing. However, traditional methods often rely on direct observation or complex and expensive biological testing to monitor and evaluate the invasive damage caused by wound healing, which can be time-consuming. Biosensors offer the advantage of precise and real-time monitoring, but existing devices are not suitable for integration with sensitive wound tissue due to their external dimensions. Here, we have designed a self-powered biosensing suture (SPBS) based on biofuel cells to accurately monitor glucose concentration at the wound site and promote wound healing. The anode of the SPBS consists of carbon nanotubes-modified carbon fibers, tetrathiafulvalene (TTF), and glucose oxidase (GOx), while the cathode is composed of Ag 2 O and carbon nanotubes modified nanotubes modified carbon fibers. It was observed that SPBS exhibited excellent physical and chemical stability in vitro. Regardless of different bending degrees or pH values, the maximum power density of SPBS remained above 92%, which is conducive to long-term dynamic evaluation. Furthermore, the voltage generated by SPBS reflects blood glucose concentration, and measurements at wound sites are consistent with those obtained using a commercially available blood glucose meter. SPBS achieves the healing effect of traditional medical sutures after complete healing within 14 days. It offers valuable insights for intelligent devices dedicated to real-time wound monitoring. [ABSTRACT FROM AUTHOR]

The article titled "A Hybrid Biofuel Cell with High Power and Operational Stability Using Electron Transfer-Intensified Mediators and Multi-Interaction Assembly" discusses a new type of biofuel cell that utilizes natural fiber and electron transfer-intensified redox mediator layers. The authors, Yoon Jang Chung, Young-Bong Choi, Cheong Hoon Kwon, Jinhan Cho, and their colleagues, explain that this approach improves electron transfer and interfacial robustness, resulting in a high power output and excellent operation stability. The article provides valuable insights for researchers interested in biofuel cells and their potential applications. [Extracted from the article]

Abiotic 3D-printed cathodes for biofuel cells were manufactured using chitosan-cellulose nanofibres-iron doped graphene hydrogels and the cold material extrusion (MEX) 3D printing technique. The subsequent pyrolysis under ammoniac flux and in-situ n-doping of 3D cathodes led to the generation of conductive 3D electrodes with macroporosity that can be tuned by adjusting the linera infill in the 3D printing process and enhanced electrochemical activity. In-situ n-doped electrodes with 40% macroporosity provided a neat increase in specific current, i.e. from 13 µA/mg of 3D electrodes containing pre-doped graphene to 35 µA/mg of pyrolyzed ones, thus showing that MEX 3D printing followed by in-situ n-doping is a promising manufacturing process for the fabrication of high current density abiotic cathodes.Graphical abstract: Abiotic 3D-printed cathodes for biofuel cells were manufactured using chitosan-cellulose nanofibres-iron doped graphene hydrogels and the cold material extrusion (MEX) 3D printing technique. The subsequent pyrolysis under ammoniac flux and in-situ n-doping of 3D cathodes led to the generation of conductive 3D electrodes with macroporosity that can be tuned by adjusting the linera infill in the 3D printing process and enhanced electrochemical activity. In-situ n-doped electrodes with 40% macroporosity provided a neat increase in specific current, i.e. from 13 µA/mg of 3D electrodes containing pre-doped graphene to 35 µA/mg of pyrolyzed ones, thus showing that MEX 3D printing followed by in-situ n-doping is a promising manufacturing process for the fabrication of high current density abiotic cathodes. [ABSTRACT FROM AUTHOR]

Biofuel cell (BFC) that transfers chemical energy into electricity is a promising candidate as an energy‐harvesting device for implantable electronics. However, there still remain major challenges for implantable BFCs, including bulky and rigid device structure mismatching with soft tissues such as the brain, and the power output decreases due to the fouling process in a biological environment. Here, a flexible and anti‐biofouling fiber BFC working in the brain chronically is developed. The fiber BFC is based on a carbon nanotube fiber electrode to possess small size and flexibility. A hydrophilic zwitterionic anti‐biofouling polydopamine‐2‐methacryloyloxyethyl phosphorylcholine layer is designed on the surface of fiber BFC to resist the nonspecific protein adsorption in a complex biological environment. After implantation, the fiber BFC can achieve a stable device/tissue interface, along with a negligible immune response. The fiber BFC has first realized power generation in the mouse brain for over a month, exhibiting its promising prospect as an energy‐harvesting device in vivo. [ABSTRACT FROM AUTHOR]

Redox enzymes can work as efficient electrocatalysts. The coupling of redox enzymatic reactions with electrode reactions is called enzymatic bioelectrocatalysis, which imparts high reaction specificity to electrode reactions with nonspecific characteristics. The key factors required for bioelectrocatalysis are hydride ion/electron transfer characteristics and low specificity for either substrate in redox enzymes. Several theoretical features of steady-state responses are introduced to understand bioelectrocatalysis and to extend the performance of bioelectrocatalytic systems. Applications of the coupling concept to bioelectrochemical devices are also summarized with emphasis on the achievements recorded in the research group of the author. [ABSTRACT FROM AUTHOR]

A spider nest shaped multi-scale three-dimensional substrate consisting of reduced graphene oxide (RGO) and nickel foam is fabricated for enzymatic electrodes and biofuel cells. According to the excellent conductivity and large electroactive surface area of this special structure, the enzymatic electrodes show large enzymatic loading density, low electron transfer resistance and high electrocatalytic efficiency. The strong forces in the spider nest shaped structure and the excellent enzymatic embedding method ensure the stability of the glucose oxidase bioanodes and laccase biocathodes. The Michaelis–Menten constant value for the bioanodes to glucose is calculated to be 2.24 mM, which is close to the Michaelis–Menten constant for free glucose oxidase, implying a remarkably high enzymatic activity. Employed the obtained bioelectrodes with great properties, the relative glucose/oxygen biofuel cell has an open-circuit voltage of 0.70 V, with a high output power performance, and a maximum output power of 7.05 ± 0.05 mW cm−2, owe to the high enzyme loading and low electron transfer resistance of the electrode based on the spider nest shaped structure. After 60 days of periodic storage experiments, the performance of the biofuel cell still maintained 84.2%, showing a good long-term stability. A unique spider nest shaped multi-scale three-dimensional substrate with extremely large specific surface area and excellent conductivity is employed to fabricate glucose/oxygen biofuel cells with remarkable electrocatalytic efficiency, great output power density and good stability. [Display omitted] • A unique spider nest shaped multi-scale three-dimensional substrate is fabricated. • The bioelectrodes show high enzymatic loading density and catalytic efficiency. • The glucose oxidase on bioanodes shows great enzymatic activity. • High power output and good stability of the biofuel cell is obtained. [ABSTRACT FROM AUTHOR]

Enzymatic biofuel cells (EBCs) using non-toxic and naturally derived flavonoid biomediators as anodic catalysts are introduced. In this study, hesperidin, a flavonoid extracted from citrus fruits, served as a biomediator with flavine adenine dinucleotide dependent glucose dehydrogenase (FADGDH). Hesperidin exhibits several advantages, including a low onset potential, a robust catalytic activity, and an excellent stability for glucose oxidation reaction (GOR). This superiority can be attributed to its unique chemical structure and electrochemically activated capability. For its activation, a catechol group was produced on the right side of the phenyl ring of hesperidin, existing in both chemically and physically adsorbed forms. Following activation, a redox reaction occurred at a buckypaper (BP) supported electrode (BP/Activated Hesperidin (A-Hesperidin)) at −0.05 and 0.15 V (vs. Ag/AgCl). When BP/A-Hesperidin/FADGDH was employed, the reactivity of GOR reached 0.61 mA cm−2 at 0.3 V with 10 mmol L−1 glucose. These performances surpass those reported in similar research studies. When the EBC using BP/A-Hesperidin/FADGDH was operated, its maximum power density (MPD) reached 212.84 ± 17.97 μW cm−2 with 10 mmol L−1 glucose under air conditions. This confirms that A-Hesperidin can induce higher EBC performances than conventionally used mediators, which are often toxic and expensive. [Display omitted] [ABSTRACT FROM AUTHOR]

Biofuel cells (BFCs) are the devices made to transform the chemical energy of organic matter to electrical energy utilizing metabolic reactions occurring in microorganisms during degradation of organic contaminants. In spite of having many applications such as waste water treatment, biosensors and portable uses of BFCs, promoting the uses of BFCs is very challenging because of short life-time and low-power density. Most of the BFC developed till date is only capable to fulfill energy needs of biomedical short-term implanted devices. Use of materials with nano dimensions in the construction of BFCs has been studied extensively and reported as a worthwhile strategy to increase its efficiency. Usually, it is difficult to achieve efficient electron transfer on planar electrode from biocatalyst due to its non-specific orientational the interface. Nonmaterials provide close wiring for the electron transfer between biocatalyst and electrode. Use of various nanomaterials is the most effective way to decrease the gap between active sites (electron producing area)deep inside the enzyme or proteins and the electrodes to achieve better electron transfer. Also, various nanomaterials are utilized to improve the membrane materials for better electron barrier. Many carbon nanostructures, conducting polymers, metal and metal oxides are promising nonmaterials to enhance the current output from BFC. This review highlights recent progress registered in the development of various nanomaterials for construction of electrode and membranes of biofuel cells for better efficiency. It also emphasized the utilization of different metallic nanomaterials, inorganic nanomaterials, conducting polymer-based nanomaterials and carbon-based nanomaterials such as graphene, fullerenes, and carbon nanotubes. [Display omitted] • A comprehensive account of biofuel cells (BFCs) is presented. • Various aspects of BFCs are critically analyzed. • Role of nanomaterials in biofuel cells is emphasized. • Current challenges in this field are mentioned. • Future prospects are also highlighted. [ABSTRACT FROM AUTHOR]

We report on a photobioelectrochemical fuel cell consisting of a glucose‐oxidase‐modified BiFeO3 photobiocathode and a quantum‐dot‐sensitized inverse opal TiO2 photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich‐like manner due to the semi‐transparent nature of BiFeO3, which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi‐artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels. [ABSTRACT FROM AUTHOR]

We report on a photobioelectrochemical fuel cell consisting of a glucose‐oxidase‐modified BiFeO3 photobiocathode and a quantum‐dot‐sensitized inverse opal TiO2 photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich‐like manner due to the semi‐transparent nature of BiFeO3, which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi‐artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels. [ABSTRACT FROM AUTHOR]

The kinetics of bioelectrocatalytic oxidation of glucose by protein extracts—supersonic-destruction products of Escherichia coli BB cells—is studied in the presence of [Fe(CN)6]3– as the mediator system. The effect of the concentration of mediator, glucose, and protein extract is studied by electrochemical methods. The results are used in determination of effective parameters: the rate constant of glucose biooxidation, the constant of substrate-induced inhibition, and the activation energy. It is shown that the activation energy of this reaction falls into the interval of activation energies of dehydrogenase reactions. The voltammetric characteristics of a model asymmetrical biofuel cell which employs the protein extract as the anodic catalyst are determined. The maximum specific power of such model biofuel cell is found to be 400 µW/cm2 (4 W/m2). [ABSTRACT FROM AUTHOR]

The incorporation of highly active but also highly sensitive catalysts (e.g. the [FeFe] hydrogenase from Desulfovibrio desulfuricans) in biofuel cells is still one of the major challenges in sustainable energy conversion. We report the fabrication of a dual‐gas diffusion electrode H2/O2 biofuel cell equipped with a [FeFe] hydrogenase/redox polymer‐based high‐current‐density H2‐oxidation bioanode. The bioanodes show benchmark current densities of around 14 mA cm−2 and the corresponding fuel cell tests exhibit a benchmark for a hydrogenase/redox polymer‐based biofuel cell with outstanding power densities of 5.4 mW cm−2 at 0.7 V cell voltage. Furthermore, the highly sensitive [FeFe] hydrogenase is protected against oxygen damage by the redox polymer and can function under 5 % O2. [ABSTRACT FROM AUTHOR]

The growing power demands of wearable electronic devices have stimulated the development of on‐body energy‐harvesting strategies. This article reviews the recent progress on rapidly emerging wearable biofuel cells (BFCs), along with related challenges and prospects. Advanced on‐body BFCs in various wearable platforms, e.g., textiles, patches, temporary tattoo, or contact lenses, enable attractive advantages for bioenergy harnessing and self‐powered biosensing. These noninvasive BFCs open up unique opportunities for utilizing bioenergy or monitoring biomarkers present in biofluids, e.g., sweat, saliva, interstitial fluid, and tears, toward new biomedical, fitness, or defense applications. However, the realization of effective wearable BFC requires high‐quality enzyme‐electronic interface with efficient enzymatic and electrochemical processes and mechanical flexibility. Understanding the kinetics and mechanisms involved in the electron transfer process, as well as enzyme immobilization techniques, is essential for efficient and stable bioenergy harvesting under diverse mechanical strains and changing operational conditions expected in different biofluids and in a variety of outdoor activities. These key challenges of wearable BFCs are discussed along with potential solutions and future prospects. Understanding these obstacles and opportunities is crucial for transforming traditional bench‐top BFCs to effective and successful wearable BFCs. [ABSTRACT FROM AUTHOR]

Fabrication of sensitive and convenient methods for the detection of heavy metal ions is an important task due to their high toxicity to environment and human health. Divalent mercury ions (Hg2+) are a kind of significant public health hazard, which generate harmful toxic effects. In this work, a novel self‐powered biosensor for the quantification of Hg2+ in aqueous solutions is developed. Porous magnetic nanoparticles are synthesized to load electrochemical species and a Hg2+ responsive single‐stranded DNA probe is used to seal them. After specific interaction with target ions, the DNA probe forms a rigid duplex, which can no longer block the pores of the magnetic nanoparticles. The leakage of electrochemical species can then increase the electrochemical response, which is used to indicate the initial concentration of Hg2+. This method shows high sensitivity and selectivity, and can be applied in real water samples with excellent recoveries. Therefore, a novel approach is provided for ultrasensitive and reliable detection of Hg2+ in practical applications. [ABSTRACT FROM AUTHOR]

Aliphatic synthetic intermediates with high added value are generally produced from alkane sources (e.g. petroleum) by inert carbon–hydrogen (C−H) bond activation using classical chemical methods (i.e. high temperature, rare metals). As an alternative approach for these reactions, alkane monooxygenase from Pseudomonas putida (alkB) is able to catalyze the difficult terminal oxyfunctionalization of alkanes selectively and under mild conditions. Herein, we report an electrosynthetic system using an alkB biocathode which produces alcohols, epoxides, and sulfoxides through bioelectrochemical hydroxylation, epoxidation, sulfoxidation, and demethylation. The capacity of the alkB binding pocket to protect internal functional groups is also demonstrated. By coupling our alkB biocathode with a hydrogenase bioanode and using H2 as a clean fuel source, we have developed and characterized a series of enzymatic fuel cells capable of oxyfunctionalization while simultaneously producing electricity. [ABSTRACT FROM AUTHOR]

Aliphatic synthetic intermediates with high added value are generally produced from alkane sources (e.g. petroleum) by inert carbon–hydrogen (C−H) bond activation using classical chemical methods (i.e. high temperature, rare metals). As an alternative approach for these reactions, alkane monooxygenase from Pseudomonas putida (alkB) is able to catalyze the difficult terminal oxyfunctionalization of alkanes selectively and under mild conditions. Herein, we report an electrosynthetic system using an alkB biocathode which produces alcohols, epoxides, and sulfoxides through bioelectrochemical hydroxylation, epoxidation, sulfoxidation, and demethylation. The capacity of the alkB binding pocket to protect internal functional groups is also demonstrated. By coupling our alkB biocathode with a hydrogenase bioanode and using H2 as a clean fuel source, we have developed and characterized a series of enzymatic fuel cells capable of oxyfunctionalization while simultaneously producing electricity. [ABSTRACT FROM AUTHOR]

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero‐dimensional materials, carbon‐based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost‐effective, environmentally friendly, biocompatible, stable and easily‐functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications. [ABSTRACT FROM AUTHOR]

A maximization of a direct electron transfer (DET) between redox enzymes and electrodes can be obtained through the oriented immobilization of enzymes onto an electroactive surface. Here, a strategy for obtaining carbon nanotube (CNTs) based electrodes covalently modified with perfectly control‐oriented fungal laccases is presented. Modelizations of the laccase‐CNT interaction and of electron conduction pathways serve as a guide in choosing grafting positions. Homogeneous populations of alkyne‐modified laccases are obtained through the reductive amination of a unique surface‐accessible lysine residue selectively engineered near either one or the other of the two copper centers in enzyme variants. Immobilization of the site‐specific alkynated enzymes is achieved by copper‐catalyzed click reaction on azido‐modified CNTs. A highly efficient reduction of O2 at low overpotential and catalytic current densities over −3 mA cm−2 are obtained by minimizing the distance from the electrode surface to the trinuclear cluster. [ABSTRACT FROM AUTHOR]

This review summarizes the bioelectrocatalytic properties of d -fructose dehydrogenase (FDH), while taking into consideration its enzymatic characteristics. FDH is a membrane-bound flavohemo-protein with a molecular mass of 138 kDa, and it catalyzes the oxidation of d -fructose to 5-keto- d -fructose. The characteristic feature of FDH is its strong direct-electron-transfer (DET)-type bioelectrocatalytic activity. The pathway of the DET-type reaction is discussed. An overview of the application of FDH-based bioelectrocatalysis to biosensors and biofuel cells is also presented, and the benefits and problems associated with it are extensively discussed. Unlabelled Image • Bioelectrocatalytic properties of d -fructose dehydrogenase (FDH) are reviewed. • Recent findings about FDH are summarized especially DET mechanism. • The application of FDH to biosensors and biofuel cells are simmarized. • The benefits and problems of FDH-based reaction are detailed for future works. [ABSTRACT FROM AUTHOR]

Summary: This study proposed an expert system approach on the basis of artificial intelligence (AI) in the modeling of cyclic voltammogram (CV) profiles of green tea extracts. AI approach of artificial neural networks is applied to generate the model phase‐plane portraits of current output versus applied voltage through CV scan cycles. The predicted current values were validated using experiments, and generic ability of approach was examined by testing on the CV scan cycles generated from Syzygium aromaticum and Citrus reticulate. It was concluded that AI approach can be employed to reveal stable point (cycle and voltage) in CV profiles for bioenergy applications. [ABSTRACT FROM AUTHOR]

Mathematical models of multi-step enzyme systems immobilized on porous electrodes are discussed. The model contains a non-linear term related to Monod kinetics. This work presents a better approximate analytical solution for non-linear differential equations of concentrations profile is derived using new approach of Homotopy perturbation method. Moreover, the derived analytical expressions are compared with numerical simulations. In addition, analytical expression for current density is derived and also it is compared with experimental data of already published work of Hettige et al [16]. The analytical expressions derived here are good enough to predict the behavior of the system. The influence of dimensionless governing parameters are discussed and presented graphically. The presented solutions are more reliable and easy to predict the dynamic behavior of the system by varying the parameters. [ABSTRACT FROM AUTHOR]

Abstract A glucose/oxygen biofuel cell (BFC) that can operate continuously under oxygen-free conditions is described. The oxygen-deficit limitations of metabolite/oxygen enzymatic BFCs have been addressed by using an oxygen-rich cathode binder material, polychlorotrifluoroethylene (PCTFE), which provides an internal oxygen supply for the BFC reduction reaction. This oxygen-rich cathode component mitigates the potential power loss in oxygen-free medium or during external oxygen fluctuations through internal supply of oxygen, while the bioanode employs glucose oxidase-mediated reactions. The internal oxygen supply leads to a prolonged energy-harvesting in oxygen-free solutions, e.g. , maintaining over 90% and 70% of its initial power during 10- and 24-h operations, respectively, in the absence of oxygen. The new strategy holds considerable promise for energy-harvesting and self-powered biosensing applications in oxygen-deficient conditions. Highlights • A glucose/O 2 biofuel cell operating continuously under oxygen-free conditions. • An O 2 -rich cathode binder material, providing internal oxygen supply for the BFC reduction reaction. • Energy-harvesting and self-powered applications in O 2 -fluctuating conditions. [ABSTRACT FROM AUTHOR]

The application of biofuel cells (BFCs) for the construction of self‐powered electrochemical biosensors has recently received enormous attention with exciting advancements. The principle of BFCs for electrochemical biosensing is that the BFCs' power output which is directly extracted by the biological reactions with the help of biocatalysts is closely related to the analyte's concentration. Such unique feature makes BFCs based electrochemical biosensors with two‐electrode system to be operated without the need of any external power source, which provides a more effective way for the miniaturization and convenient construction of electrochemical biosensors than the traditional electrochemical biosensors with three‐electrode system. Following our previous reviews (Electroanalysis 2012, 24, 197–209; Electroanalysis 2015, 27, 1786–1801), the current review is focused on the recent development and advances in the construction of BFCs based self‐powered electrochemical biosensors which are reported in the years between 2015 and 2018, with a particular emphasis on their possible practical applications in the fields of medical diagnosis, environmental monitoring, food analysis and wearable devices. For these reported BFCs‐based self‐powered electrochemical biosensors, the design approaches are still within the scope of effects (i.e., substrate, inhibition, blocking, gene regulation, enzyme, co‐stabilization, competition, and hybrid effects) summarized by our previous reviews. The outlook, challenges and developing tendency of the future research for the construction of BFCs based self‐powered electrochemical biosensor are discussed in the end. We expect that the advanced electrochemical biosensors based on BFCs with the unique self‐powered capability will continue attracting increasing research interest and lead to new opportunities in various attractive applications related to analytical chemistry. [ABSTRACT FROM AUTHOR]

Abstract: In the development of biofuel cells great effort is dedicated to achieving outstanding figures of merit, such as high stability, maximum power output, and a large open circuit voltage. Biofuel cells with immobilized redox mediators, such as redox polymers with integrated enzymes, show experimentally a substantially higher open circuit voltage than the thermodynamically expected value. Although this phenomenon is widely reported in the literature, there is no comprehensive understanding of the potential shift, the high open circuit voltages have not been discussed in detail, and hence they are only accepted as an inherent property of the investigated systems. We demonstrate that this effect is the result of a Nernstian shift of the electrode potential when catalytic conversion takes place in the absence or at very low current flow. Experimental evidence confirms that the immobilization of redox centers on the electrode surface results in the assembled biofuel cell delivering a higher power output because of charge storage upon catalytic conversion. Our findings have direct implications for the design and evaluation of (bio)fuel cells with pseudocapacitive elements. [ABSTRACT FROM AUTHOR]

Abstract Glucose oxidase can catalyze the oxidization of glucose in the mild conditions, which can be used to decorate the anode of the biofuel cells. The carbon nanotube electrode can direct contact with the flavin adenine dinucleotide cofactor of glucose oxidase by automatic absorption. Our ab initio calculations reveal that proton/electron transfer from β- d -glucose to isoaloxazine ring occurs via a proton-coupled double-electron transfer mechanism according to a model including deprotonated glucose and lumiflavin with a high energy barrier of 30.5 kcal/mol. The similar result is obtained from the examination of the corresponding reaction in glucose oxidase at the ONIOM(M06–2X/6-31 + G(d,p):amber) level. When the isoalloxazine ring directly interacts with the surface of carbon nanotube in the glucose-oxidase-modified electrode, however, the reaction occurs through a π-π-driven proton-coupled double-electron transfer mechanism with a low energy barrier (0.2–12.0 kcal/mol). This is because that the π-π interaction plays a central role in promoting electron transfer from substrate to flavin. These findings indicate that the association of glucose oxidase and carbon nanotube is a potential application for the effective electrode of enzymatic biofuel cell. Highlights • Proton-coupled ET from glucose to FAD occurs with a high energy barrier. • Direct interactions of CNT with FAD greatly promote PT/ET from glucose to FAD. • Direct interaction of CNT with FAD can achieve direct ET from GOx to electrode. • CNTs hold great promise for constructing glucose-oxidase-modified electrode. [ABSTRACT FROM AUTHOR]

Electrode supports play a significant role in the assembly of high-performance biofuel cells (BFCs) since they connect the active center of biocatalysts and the charge collectors directly. In this manuscript, novel nanostructured multi-walled carbon nanotube (MWCNT) films were fabricated by electrophoretic deposition (EPD-MWCNT films) as electrode supports for high-performance BFCs. Flavin adenine dinucleotide-dependent glucose dehydrogenase and laccase were modified on EPD-MWCNT films to fabricate the bioanodes and biocathodes, respectively, with Os-complexes as mediators. For comparison, drop-casted MWCNT films or buckypapers have been prepared and adopted for the construction of BFCs with the same biocatalysts. EPD-MWCNT films which have vegetable sponge-like networks should be the optimal electrode supports for glucose/O 2 BFCs with higher power density. The EPD-MWCNT films based glucose/O 2 BFC showed a high maximum power density of 0.43 ± 0.03 mW cm −2 and open circuit voltage of 0.59 V, which is significantly superior to those values of the BFCs based on drop-cast MWCNT films or buckypapers, contributing to the electrode supports of EPD-MWCNT films with vegetable sponge-like nanostructure. Moreover, the BFC retained 56% of its original power density even after continuous operation for 7 days. Our findings would open an avenue for the development of more efficient BFCs with EPD-MWCNT films as the electrode supports. [ABSTRACT FROM AUTHOR]

Bioelectrocatalytic carbon nanotube pellets comprising glucose oxidase (GOx) at the anode and horseradish peroxidase (HRP) at the cathode were integrated in a glucose/H 2 O 2 flow-through fuel cell setup. The porous bioelectrodes, separated with a cellulose membrane, were assembled in a design allowing the fuel/electrolyte flow through the entire fuel cell with controlled direction. An air saturated 5 mmol L −1 glucose solution was directed through the anode where glucose is used for power conversion and for the enzymatic generation of hydrogen peroxide supplying the HRP biocathode with its substrate. This configuration showed an open circuit voltage (OCV) of 0.6 V and provided 0.7 ± 0.035 mW at 0.41 V. Furthermore, different charge/discharge cycles at 500 Ω and 3 kΩ were applied to show the long term stability of this setup producing 290 μW h (1.04 J) of energy after 48 h. The biofuel cell design further allows a convenient assembly of several glucose biofuel cells in reduced volumes and its connection in parallel or in series. [ABSTRACT FROM AUTHOR]

Abstract: Herein, the direct electrochemistry of bilirubin oxidase from Magnaporthe orizae (MoBOD) was studied on CNTs functionalized by electrografting several types of diazonium salts. The functionalization induces favorable or unfavorable orientation of MoBOD, the latter being compared to the well‐known BOD from Myrothecium verrucaria (MvBOD). On the same nanostructured electrodes, MoBOD can surpass MvBOD in terms of both current densities and minimal overpotentials. Added to the fact that MoBOD is also highly active at the gas‐diffusion electrode (GDE), these findings make MoBOD one of the MCOs with the highest catalytic activity towards the oxygen reduction reaction (ORR). [ABSTRACT FROM AUTHOR]

Over the last three decades, there has been a large increase in the production and use of biofuels. This has led researchers to study alternative strategies for converting biofuel energy into electrical energy. This review starts with an introduction to the field, including a brief discussion of the production of common biofuels from a variety of biomass sources. The main focus of the review is on the variety of catalytic materials that have been developed for biofuel conversion of chemical energy to electrical energy. The scope of the article ranges from soft materials (organic and biological catalysts) to metallic catalytic materials to ceramic catalytic materials. The review covers biofuels from biohydrogen to bioethanol to biodiesel to glycerol to glucose. As a critical review, this review describes the state-of-the-art electrocatalysts for biofuel oxidation and provides a critical discussion of the practical properties of desired catalytic materials and areas of need for the coming decade. [ABSTRACT FROM PUBLISHER]

In this work, high-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co3O4 nanododecahedras in situ decorated on carbon nanotubes (3D Co3O4-HPND/CNTs) were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. The morphology, microstructure, and composite of 3D Co3O4-HPND/CNTs were characterized by scanning electron microscopy, transmission electron microscopy, micropore and chemisorption analyzer, and X-ray diffraction. The electrochemical characterizations indicated that 3D Co3O4-HPND/CNTs present considerably catalytic activity toward glucose oxidation and could be promising for constructing high-performance electrochemical non-enzymatic glucose sensors and glucose/O2 biofuel cell. When used for non-enzymatic glucose detection, the 3D Co3O4-HPND/CNTs modified glassy carbon electrode (3D Co3O4-HPND/CNTs/GCE) exhibited excellent analytical performance with high sensitivity (22.21 mA mM−1 cm−2), low detection limit of 0.35 μM (S/N = 3), fast response (less than 5 s) and good stability. On the other hand, when the 3D Co3O4-HPND/CNTs/GCE worked as an anode of a biofuel cell, a maximum power density of 210 μW cm−2 at 0.15 V could be obtained, and the open circuit potential was 0.68 V. The attractive 3D hierarchical porous structural features, the large surface area, and the excellent conductivity based on the continuous and effective electron transport network in 3D Co3O4-HPND/CNTs endow 3D Co3O4-HPND/CNTs with the enhanced electrochemical performance and promising applications in electrochemical sensing, biofuel cell, and other energy storage and conversion devices such as supercapacitor.High-performance non-enzymatic catalysts for enzymeless glucose sensing and biofuel cell based on 3D hierarchical hollow porous Co3O4 nanododecahedras anchored on carbon nanotubes were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. [ABSTRACT FROM AUTHOR]

Environmental and sustainable economical concerns are generating a growing interest in biofuels predominantly produced from biomass. It would be ideal if an energy conversion device could directly extract energy from a sustainable energy resource such as biomass. Unfortunately, up to now, such a direct conversion device produces insufficient power to meet the demand of practical applications. To realize the future of biofuel-fed fuel cells as a green energy conversion device, efforts have been devoted to the development of carbon-based nanomaterials with tunable electronic and surface characteristics to act as efficient metal-free electrocatalysts and/or as supporting matrix for metal-based electrocatalysts. We present here a mini review on the recent advances in carbon-based catalysts for each type of biofuel-fed/biofuel cells that directly/indirectly extract energy from biomass resources, and discuss the challenges and perspectives in this developing field. [ABSTRACT FROM AUTHOR]

A bioanode for ethanol oxidation was prepared by immobilizing the recombinant pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenase from Pseudomonas putida KT 2440 (PpADH) with polyion complex (PIC) and redox polymer. The PIC based on poly-L-lysine (PLL) and poly-L-glutamic acid (PGA) was suitable for immobilizing PpADH on the electrode. PpADH was immobilized using only one redox polymer, aminoferrocene, which was attached to the PGA backbone (PGA-AmFc) on the electrode. The anodic current density at 0.6 V (vs. Ag/AgCl) was 22.6 µA·cm-2However, when the number of the cycles was increased, the catalytic current drastically decreased. PpADH was immobilized using PGA-AmFc and PIC on the electrode. The anodic current density at 0.5 V (vs. Ag/AgCl) was 47.3 µA·cm-2 and the performance maintained 74% of the initial value after five cycles. This result indicated that the combination of PIC and PGA-AmFc was suitable for the immobilization of PpADH on the electrode. In addition, the long-term stability and catalytic current density were improved by using the large surface area afforded by the gold nanoparticles. [ABSTRACT FROM AUTHOR]