Electrochemical study of single wall carbon nanotubes/graphene/ferritin composite for biofuel cell applications

A single wall carbon nanotubes (SWNTs)/graphene/ferritin/GOx layer on a glassy carbon electrode (GCE) acting as a biofuel cell anode was fabricated using a SWNTs/graphene/ferritin composite as an electron transfer mediator from the enzyme to the electrode. In the presence of glucose, the SWNTs/graphene/ferritin/GOx composite showed a higher current response than SWNTs/graphene/GOx composite and the electrocatalytic oxidation of glucose on the anode increased linearly with increasing concentration of glucose. The highly distributed SWNTs/graphene/ferritin composite acts as a platform for enzyme immobilization resulted in an enhanced electrocatalytic activity towards glucose. The SWNTs/graphene/ferritin composite showed an enhanced electron transfer from enzyme to the electrode; therefore, SWNTs/graphene/ferritin/GOx composite can be used as an anode in biofuel cells.     

A promising dehydrogenase-based bioanode for a glucose biosensor and glucose/O2 biofuel cell

A new type of dehydrogenase-based amperometric glucose biosensor was constructed using glucose dehydrogenase (GDH) which was immobilized on the edge-plane pyrolytic graphite (EPPG) electrode modified with poly(phenosafranin)-functionalized single-walled carbon nanotubes (PPS-SWCNTs). The PPS-SWCNT-modified EPPG electrode was prepared by electropolymerization of phenosafranin on the EPPG electrode which had been previously coated with SWCNTs. The performance of the GDH/PPS-SWCNT/EPPG bioanode was evaluated using cyclic voltammetry and amperometry in the presence of glucose. The GDH/PPS-SWCNT/EPPG electrode possesses promising characteristics as a glucose sensor: a wide linear dynamic range of 50 to 700 μM, low detection limit of 0.3 μM, fast response time (1-2 s), high sensitivity (96.5 μA cm(-2) mM(-1)), and anti-interference and anti-fouling abilities. Moreover, the performance of the GDH/PPS-SWCNT/EPPG bioanode was tested in a glucose/O(2) biofuel cell. The maximum power density delivered by the assembled glucose/O(2) biofuel cell could reach 64.0 μW cm(-2) at a cell voltage of 0.3 V with 40 mM glucose.     

固酶氮掺杂碳纳米复合物基燃料电池性能

利用掺杂氮介孔材料(NDMPC)和羧甲基壳聚糖(CMCH)机械共混的纳米复合物作为固酶载体,以滴涂-干燥法分别制备了固定漆酶(Lac)阴极和固定葡萄糖氧化酶阳极,组装了有Nafion离子交换膜的葡萄糖/O₂酶燃料电池.固定漆酶电极作为燃料电池阴极和氧电化学传感器的性能以结合旋转圆盘电极技术的循环伏安法、线性扫描伏安(LSV)法以及计时电流法进行表征,同时使用紫外-可见分光光度法和石墨炉原子吸收光谱法研究酶分子在电极表面的构型和估算电极表面载体对酶的担载量.测试结果表明:固酶阴极在无电子中介体时可以实现漆酶活性中心T₁与导电基体之间的直接电子迁移(表观电子迁移速率为0.013 s^-1),而且具有较小的氧还原超电势(150 mV).通过进一步定量比较分子内电子传递速率(1000 s^-1)、底物转化速率(0.023 s^-1)以及前述酶-导电基体间电子迁移速率,可以发现此电极催化氧还原循环受制于酶-电极之间的电子迁移过程;这种电极对氧的传感性能良好:低检测限(0.04 μmol·dm^-3)、高灵敏度(12.1 μA·μmol^-1·dm³)和良好的对氧亲和力(K_M = 8.2 μmol·dm^-3),这种固酶阴极还具有良好的重现性、长期使用性、热稳定性和pH耐受性.组装的生物燃料电池的开路电压为0.38 V,最大能量输出密度为19.2 μW·cm^-2,最佳工作条件下使用3周后输出功率密度仍可保持初始值的60%以上.     

An easy compartment-less biofuel cell construction based on the physical co-inclusion of enzyme and mediator redox within pressed graphite discs

We report on the easy and fast immobilization of glucose oxidase (GOD) and laccase by mechanical compression with graphite particles to form disc electrodes. The electrical wiring of GOD and laccase was efficiently carried out by their co-inclusion with ferrocene (Fc) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) respectively. A glucose/air compartment-less biofuel cell was constructed based on the association of GOD-ferrocene-graphite disc and laccase-ABTS – graphite disc electrodes as bioanode and biocathode respectively. Such biofuel cell yielded a power density of 23 μW cm^?2 at 0.33 V as well as an open-circuit voltage and a short-circuit current of 0.63 V and 166 μA, respectively.     

A Membraneless Glucose/O2 Biofuel Cell Based on Pd Aerogels

In this study, we introduce the first membraneless glucose/O₂ biofuel cell using Pd‐based aerogels as electrode materials. The bioanode was fabricated with a coimmobilized mediator and glucose oxidase for the oxidation of glucose, in which ferrocenecarboxylic acid was integrated into a three‐dimensional porous beta‐cyclodextrin‐modified Pd aerogel to mediate the bioelectrocatalytic reaction. Bilirubin oxidase and Pd–Pt alloy aerogel were confined to an electrode surface, which realized the direct bioelectrocatalytic function for the reduction of O₂ to H₂O with a synergetic effect at the biocathode. By employing these two bioelectrodes, the assembled glucose/O₂ biofuel cell showed a maximum power output of 20 μW cm^?2 at 0.25 V.     

Biocatalytic anode for glucose oxidation utilizing carbon nanotubes for direct electron transfer with glucose oxidase

Covalently linked layers of glucose oxidase, single-wall carbon nanotubes and poly-l-lysine on pyrolytic graphite resulted in a stable biofuel cell anode featuring direct electron transfer from the enzyme. Catalytic response observed upon addition of glucose was due to electrochemical oxidation of FADH₂ under aerobic conditions. The electrode potential depended on glucose concentration. This system has essential attributes of an anode in a mediator-free biocatalytic fuel cell.     

V(IV)在不同电极上氧化还原动力学研究

分别以导电塑料集流板、石墨棒、铂片作工作电极,应用循环伏安法和稳态极化法研究V(IV)的阳极氧化动力学过程,计算V(IV)在不同材料电极上的反应动力学参数.结果表明,以导电塑料板作电极,硫酸氧钒有较宽的水稳定区,且析氧电位较高;在石墨电极上,V(V)/V(IV)的交换电流密度较大,表现出较好的可逆性;而在铂电极上,硫酸氧钒更易析氢.     

Biofuel Cell Based on Anode and Cathode Modified by Glucose Oxidase

A single compartment biofuel cell (BFC) based on an anode and a cathode powered by the same fuel glucose is reported. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose consuming biocatalyst for both anode and cathode of the BFC. The 5‐amino‐1,10‐phenanthroline modified graphite rod electrode (GRE) with cross‐linked GOx was used as the bioanode, and the GRE with co‐immobilised horseradish peroxidase and GOx was exploited as the biocathode of the BFC. The open‐circuit voltage of the designed BFC exceeded 450 mV and a maximal power density of 3.5 µW/cm² was registered at a cell voltage of 300 mV.     

Glucose Biosensor Based on Carbon/PVC-COOH/Ferrocene Composite with Covalently Immobilized Enzyme

A carbon/PVC-COOH/ferrocene composite electrode used for the determination of glucose has been prepared. The ferrocene acted as mediator was incorporated into the PVC-COOH polymer and the leakage could be prevented. The presence of carboxyl groups on the electrode surface allowed immobilizing enzyme via EDC and NHS. The ratio of PVC-COOH to graphite powder （w/w） has been studied. Amperometric determination of glucose has been performed at potential of 0.30 V vs SCE. The response time was 〈 15 s. The linear response range was of 0.1-20 mmol/L with a detection limit of 48μmol/L.     

Mediated Bioelectrocatalytic Oxidation of Glucose on a Glucose Oxidase-Containing Composite

A composite material, which includes glucose oxidase (GOD), finely divided colloidal graphite, ferrocene, and Nafion, is developed and investigated. Kinetic parameters of redox conversions of GOD and flavin adenine dinucleotide, which is present in the active center of GOD, indicate that GOD in the composite retains molecular integrity and enzymic activity. Ferrocene in the composite undergoes reversible oxidation and is reduced on the electrode. Bioelectrocatalytic oxidation of glucose on the composite occurs via a mediator path, and the half-wave potential of a polarization curve recorded on the electrode in the presence of glucose coincides with the redox potential of ferrocene, which is equal to 0.32 V (Ag/AgCl). Effect of the ferrocene amount in the composite and the glucose concentration in the bulk solution on the glucose oxidation is studied. The results are used to optimize the composite's composition to ensure a stable operation of the enzyme electrode and effective glucose oxidation.     

Study on Glucose Biofuel Cells Using an Electrochemical Noise Device

An electrochemical noise (ECN) device was utilized for the first time to study and characterize a glucose/O₂ membraneless biofuel cell (BFC) and a monopolar glucose BFC. In the glucose/O₂ membraneless BFC, ferrocene (Fc) and glucose oxidase (GOD) were immobilized on a multiwalled carbon nanotubes (MWCNTs)/Au electrode with a gelatin film at the anode; and laccase (Lac) and an electron mediator, 2,2′‐azinobis (3‐ethylbenzothiazoline‐6‐sulfonate) diammonium salt (ABTS), were immobilized on a MWCNTs/Au electrode with polypyrrole at the cathode. This BFC was performed in a stirred acetate buffer solution (pH 5.0) containing 40 mmol/L glucose in air, with a maximum power density of 8 μW/cm², an open‐circuit cell voltage of 0.29 V, and a short‐circuit current density of 85 μA/cm², respectively. The cell current at the load of 100 kΩ retained 78.9% of the initial value after continuous discharging for 15 h in a stirred acetate buffer solution (pH 5.0) containing 40 mmol/L glucose in air. The performance decrease of the BFC resulted mainly from the leakage of the ABTS mediator immobilized at the cathode, as revealed by the two‐channel quartz crystal microbalance technique. In addition, a monopolar glucose BFC was performed with the same anode as that in the glucose/O₂ membraneless BFC in a stirred phosphate buffer solution (pH 7.0) containing 40 mmol/L glucose, and a carbon cathode in Nafion‐membrane‐isolated acidic KMnO₄, with a maximum power density of 115 μW/cm², an open‐circuit cell voltage of 1.24 V, and a short‐circuit current density of 202 μA/cm², respectively, which are superior to those of the glucose/O₂ membraneless BFC. A modification of the anode with MWCNTs for the monopolar glucose BFC increased the maximum power density by a factor of 1.8. The ECN device is highly recommended as a convenient, real‐time and sensitive technique for BFC studies.     

Electrochemical performance of pre-lithiated graphite as negative electrode in lithium-ion capacitors

Electrochemical performance of the pre-lithiated graphite and the as-assembled lithium-ion capacitors (LICs) were investigated within the Li/graphite two-electrode cell and activated carbon (AC)/graphite two-electrode cell, respectively. The morphologies of the electrodes were characterized by scanning electron microscopy (SEM). The Li intercalation of Li/graphite two-electrode cell was performed using short circuiting and galvanostatic charging techniques. The Li pre-doping process was characterized by electrochemical impedance spectroscopy (EIS). The cycle performance of the LICs were investigated at the rates of 1–20 C between the cut-off voltage at 2 to 4 V. The results demonstrated that the LIC cells with 8 h pre-doping time have the best cycle performance at the high rate of 10 C. Li pre-doping methodology plays a crucial role in the electrochemical performance of the graphite electrode and the as-assembled LICs.     

Enzymatic electrodes nanostructured with functionalized carbon nanotubes for biofuel cell applications

Nanostructured bioelectrodes were designed and assembled into a biofuel cell with no separating membrane. The glassy carbon electrodes were modified with mediator-functionalized carbon nanotubes. Ferrocene (Fc) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) bound chemically to the carbon nanotubes were found useful as mediators of the enzyme catalyzed electrode processes. Glucose oxidase from Aspergillus niger AM-11 and laccase from Cerrena unicolor C-139 were incorporated in a liquid-crystalline matrix-monoolein cubic phase. The carbon nanotubes–nanostructured electrode surface was covered with the cubic phase film containing the enzyme and acted as the catalytic surface for the oxidation of glucose and reduction of oxygen. Thanks to the mediating role of derivatized nanotubes the catalysis was almost ten times more efficient than on the GCE electrodes: catalytic current of glucose oxidation was 1 mA cm⁻² and oxygen reduction current exceeded 0.6 mA cm⁻². The open circuit voltage of the biofuel cell was 0.43 V. Application of carbon nanotubes increased the maximum power output of the constructed biofuel cell to 100 μW cm⁻² without stirring of the solution which was ca. 100 times more efficient than using the same bioelectrodes without nanotubes on the electrode surface.     

A PVC/TTF‐TCNQ Composite Electrode for Use as a Detector in Flow Injection Analysis

A new polyvinyl chloride (PVC)/tetrathiafulvalene‐tetracyanoquinodimethane (TTF‐TCNQ) composite electrode was prepared and tested for electroanalytical performance. Different PVC/TTF‐TCNQ–graphite proportions were used in order to obtain the best possible detector for accommodation in a wall‐jet electrochemical cell of use in flow injection analysis. A PVC/TTF‐TCNQ w/w ratio of 1/10 provided the best results in terms of sensitivity, coefficients of variation and mechanical resistance. The voltammetric and flow‐injection amperometric detection responses of the electrode to ascorbic acid (AA) were measured and compared with those of a PVC–graphite electrode. The resulting electrode provided good electrode kinetics with a low background current and a relatively reproducible signal. In addition, the electrode can be readily prepared and its surface readily renewed.     

Study on the United Glucose Oxidase Electrode Constructed by Composite Electrode

A novel type of united glucose oxidase (GOD) electrode was designed. Glucose oxidase and ferrocene (Fc), which was a mediator, were added into the composite electrode that was constructed by graphite powder, acetylene black, and epoxy resin. These three materials in composite electrode kept constant proportion in weight. And the optimum amounts of GOD and Fc among united enzyme electrode were 5% and 2%, respectively. The glucose was detected linearly in the concentration range 0.01–9.0 mM with a 20-s steady-state response time and 36 nA/mM of the sensitivity at 0.15 V applied potential. And electrode fouling problem and the response current from the interferents were avoided. The response current of the united GOD electrode had no obvious deterioration within 80 days when stored at 4°C in a refrigerator. The detecting results of human serum by the united GOD electrode had good consistency with that by standard enzyme method. The maximum deviation between these two detecting values was 5%. It might be used for detecting the blood sugar in clinical assay.     

Glucose Oxidase/Cellulose–Carbon Nanotube Composite Paper as a Biocompatible Bioelectrode for Biofuel Cells

Biofuel cells are devices for generating electrical energy directly from chemical energy of renewable biomass using biocatalysts such as enzymes. Efficient electrical communication between redox enzymes and electrodes is essential for enzymatic biofuel cells. Carbon nanotubes (CNTs) have been recognized as ideal electrode materials because of their high electrical conductivity, large surface area, and inertness. Electrodes consisting entirely of CNTs, which are known as CNT paper, have high surface areas but are typically weak in mechanical strength. In this study, cellulose (CL)–CNT composite paper was fabricated as electrodes for enzymatic biofuel cells. This composite electrode was prepared by vacuum filtration of CNTs followed by reconstitution of cellulose dissolved in ionic liquid, 1-ethyl-3-methylimidazolium acetate. Glucose oxidase (GOx), which is a redox enzyme capable of oxidizing glucose as a renewable fuel using oxygen, was immobilized on the CL–CNT composite paper. Cyclic voltammograms revealed that the GOx/CL–CNT paper electrode showed a pair of well-defined peaks, which agreed well with that of FAD/FADH_2, the redox center of GOx. This result clearly shows that the direct electron transfer (DET) between the GOx and the composite electrode was achieved. However, this DET was dependent on the type of CNTs. It was also found that the GOx immobilized on the composite electrode retained catalytic activity for the oxidation of glucose.     

Immobilization of hydroquinone through a spacer to polymer grafted on carbon black for a high-surface-area biofuel cell electrode

We immobilized hydroquinone through a spacer to polymer grafted on carbon black and achieved a high-surface-area biofuel cell electrode. Quinone compounds are well-known to transfer electrons in the respiratory chain and have been considered prospective mediators in biofuel cells because of their relatively negative redox potentials. Evaluation of three different spacer arms tethering hydroquinone to linear polymers revealed that only the hydrophilic and flexible di(ethylene oxide) spacer made it possible for immobilized hydroquinone to transfer electrons from glucose oxidase (GOD) to an electrode; direct immobilization and an alkyl spacer did not. The electrode comprising hydroquinone immobilized through di(ethylene oxide) spacer to polymer grafted on carbon black transferred electrons from GOD to the electrode. The potential at which an anodic current began to increase was more negative by about 0.2 V than that for a vinylferrocene-mediated electrode, while the increase in the anodic current density was of the same order.     

Synthesis of graphene oxide nanosheet: A novel glucose sensor based on nickel-graphene oxide composite film

The graphene oxide (GO) nanosheets were produced by chemical conversion of graphite, and were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR). An electrochemical sensor based on Ni/graphene (GR) composite film was developed by incorporating Ni²⁺ into the graphene oxide film modified glassy carbon electrode (Ni/GO/GCE) through the electrostatic interactions with negatively charged graphene oxide. The Ni²⁺/graphene modified glassy carbon electrode (Ni/GR/GCE) was prepared by cyclic voltammetric scanning of Ni/GO/GCE in the potential range from ?1.5 to 0.2 V at 50 mV s^?1 for 5 cycles. The electrochemical activity of Ni/GR/GCE was illustrated in 0.10 M NaOH using cyclic voltammetry. The Ni/GR/GCE exhibits the characteristic of improved reversibility and enhanced current responses of the Ni(III)/Ni(II) couple. The introduction of conductive graphene not only greatly facilitates the electron transfer of Ni²⁺, but also dramatically improves the long-term stability of the sensor by providing the electrostatic interactions. Ni/GR/GCE also shows good electrocatalytic activity toward the oxidation of glucose. The Ni/GR/GCE gives a good linear range over 10 to 2700 μM with a detection limit of 5 μM towards the determination of glucose by amperometry. This sensor keeps over 85% activity towards 0.1 mM glucose after being stored in air for a month, respectively. Furthermore, the modified sensor was successfully applied to the sensitive determination of glucose in blood samples.     

Porphyrin-sensitized nanoparticulate TiO2 as the photoanode of a hybrid photoelectrochemical biofuel cell

Porphyrin-sensitized nanoparticulate TiO(2) on conducting glass has been investigated as a photoanode material for a new cell that converts light energy into electricity. The cell is a hybrid of a dye-sensitized nanoparticulate semiconductor photoelectrochemical solar cell, and a biofuel cell that oxidizes glucose. Porphyrin molecules excited by light inject electrons into the photoanode, from where they enter the external circuit. The resulting porphyrin radical cations are reduced by NADH in aqueous buffer, ultimately regenerating the photoanode and producing NAD(+). Glucose dehydrogenase oxidizes glucose, and in the process recycles NAD(+) back to NADH. The photoanode is coupled with a suitable cathode to make a functioning cell (Hg/Hg(2)SO(4) was employed for evaluation purposes). The cell produces 1.1 V at open circuit and has a fill factor of 0.61. These values are both significantly higher than those for a previously reported cell of a similar type based on an SnO(2) electrode.     

FeFe]-hydrogenase-catalyzed H2 production in a photoelectrochemical biofuel cell

The Clostridium acetobutylicum [FeFe]-hydrogenase HydA has been investigated as a hydrogen production catalyst in a photoelectrochemical biofuel cell. Hydrogenase was adsorbed to pyrolytic graphite edge and carbon felt electrodes. Cyclic voltammograms of the immobilized hydrogenase films reveal cathodic proton reduction and anodic hydrogen oxidation, with a catalytic bias toward hydrogen evolution. When corrected for the electrochemically active surface area, the cathodic current densities are similar for both carbon electrodes, and approximately 40% of those obtained with a platinum electrode. The high surface area carbon felt/hydrogenase electrode was subsequently used as the cathode in a photoelectrochemical biofuel cell. Under illumination, this device is able to oxidize a biofuel substrate and reduce protons to hydrogen. Similar photocurrents and hydrogen production rates were observed in the photoelectrochemical biofuel cell using either hydrogenase or platinum cathodes.