Electron Transfer Rate Constant Research Articles

New Insight into Procedure of Interface Electron Transfer through Cascade System with Enhanced Photocatalytic Activity.

Recombination of photogenerated electron-hole pairs is extremely limited in the practical application of photocatalysis toward solving the energy crisis and environmental pollution. A rational design of the cascade system (i.e., rGO/Bi2 WO6 /Au, and ternary composites) with highly efficient charge carrier separation is successfully constructed. As expected, the integrated system (rGO/Bi2 WO6 /Au) shows enhanced photocatalytic activity compared to bare Bi2 WO6 and other binary composites, and it is proved in multiple electron transfer (MET) behavior, namely a cooperative electron transfer (ET) cascade effect. Simultaneously, UV-vis/scanning electrochemical microscopy is used to directly identify MET kinetic information through an in situ probe scanning technique, where the "fast" and "slow" heterogeneous ET rate constants (Keff ) of corresponding photocatalysts on the different interfaces are found, which further reveals that the MET behavior is the prime source for enhanced photocatalytic activity. This work not only offers a new insight to study catalytic performance during photocatalysis and electrocatalysis systems, but also opens up a new avenue to design highly efficient catalysts in photocatalytic CO2 conversion to useful chemicals and photovoltaic devices.

Highly sensitive and selective electrochemical sensor for detection of vitamin B12 using an Au/PPy/FMNPs@TD-modified electrode

A new electrochemical sensor for sensitive and selective detection of vitamin B12 (VB12) was constructed by the electropolymerization of pyrrole (Py) in the presence of ferromagnetic nanoparticle-incorporated triazine dendrimer (FMNPs@TD) on a gold electrode (Au). The gold/polypyrrole/ferromagnetic nanoparticles/triazine dendrimer (Au/PPy/FMNPs@TD) electrode showed electrocatalytic activity for the reduction of VB12 in Britton-Robinson buffers. The performance and interaction of the Au/PPy/FMNPs@TD with VB12 were investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetric (DPV), UV–vis spectroelectrochemistry, and density functional theory calculations. The resulting sensor exhibited excellent performance for determination of VB12 with a wide linear range (2.50 nM–0.5 μM), highly reproducible response (RSD of 2.3%), low percentage of interferences, and long-term stability. The limit of detection (LOD) and limit of quantitation (LOQ) values for the determination of VB12 were 0.91 and 3.00 nM, respectively. The electron transfer rate constants (ks), charge transfer coefficient (α), surface concentrations of electroactive species (Г), and disproportionation equilibrium constant (KD) for Au/PPy/FMNPs@TD-modified electrodes were calculated. Finally, the constructed sensor was applied to the determination of VB12 in food samples.

Electrogenerated Chemiluminescence Imaging of Electrocatalysis at a Single Au‐Pt Janus Nanoparticle

Noble metal nanoparticles are promising catalysts in electrochemical reactions, while understanding the relationship between the structure and reactivity of the particles is important to achieve higher efficiency of electrocatalysis, and promote the development of single-molecule electrochemistry. Electrogenerated chemiluminescence (ECL) was employed to image the catalytic oxidation of luminophore at single Au, Pt, and Au-Pt Janus nanoparticles. Compared to the monometal nanoparticles, the Janus particle structure exhibited enhanced ECL intensity and stability, indicating better catalytic efficiency. On the basis of the experimental results and digital simulation, it was concluded that a concentration difference arose at the asymmetric bimetallic interface according to different heterogeneous electron-transfer rate constants at Au and Pt. The fluid slip around the Janus particle enhanced local redox reactions and protected the particle surface from passivation.

Photoinduced Bimolecular Electron Transfer in Ionic Liquids: Cationic Electron Donors.

Recently, we have reported a systematic study of photoinduced electron-transfer reactions in ionic liquid solvents using neutral and anionic electron donors and a series of cyano-substituted anthracene acceptors [ Wu , B. ; Maroncelli , M. ; Castner , E. W. Jr Photoinduced Bimolecular Electron Transfer in Ionic Liquids . J. Am. Chem. Soc. 139 , 2017 , 14568 ]. Herein, we report complementary results for a cationic class of 1-alkyl-4-dimethylaminopyridinium electron donors. Reductive quenching of cyano-substituted anthracene fluorophores by these cationic quenchers is studied in solutions of acetonitrile and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Varying the length of the alkyl chain permits tuning of the quencher diffusivities in solution. The observed quenching kinetics are interpreted using a diffusion-reaction analysis. Together with results from the prior study, these results show that the intrinsic electron-transfer rate constant does not depend on the quencher charge in this family of reactions.

Development of a third generation biosensor to determine hydrogen peroxide based on a composite of soybean peroxidase/chemically reduced graphene oxide deposited on glassy carbon electrodes

A third generation enzymatic biosensor is developed to determine H2O2. The biosensor is based on the use of a composite obtained from soybean peroxidase enzyme and chemically reduced graphene oxide deposited at glassy carbon electrodes. Experiments were carried out in 0.1 M phosphate buffer solutions, pH 7.0.Cyclic voltammograms of the biosensor show two reduction peaks centered at about 0.15 and −0.4 V, respectively. A quasi-reversible redox couple is defined in the region of potentials of the first peak, which is assigned to the reduction/oxidation of compound II involved in the catalytic cycle of peroxidases. The surface concentration of the electroactive enzyme was (1.1 ± 0.2) × 10−10 mol cm−2. Values of 0.33 and 0.04 s−1 were determined for the cathodic charge transfer coefficient and the heterogeneous electron transfer rate constant, respectively. UV–vis spectroscopy and scanning electron microscopy (SEM) were used to demonstrate the chemical reduction of graphene oxide. Electrochemical impedance spectroscopy was used to characterize the different stages in the process of the electrode surface modification.Amperometric measurements were performed at a potential of −0.090 V vs. Ag/AgCl. Current responses were linear in the concentration range from 1.5 × 10−7 to 3.0 × 10−6 M. The limit of detection, limit of quantification, reproducibility, and repeatability were 5 × 10−8 M, 1.5 × 10−7 M, 9%, and 4%, respectively. The biosensor was stable during five days. The Michaelis Menten apparent constant was 1.6 × 10−6 M. The presence of uric acid, glucose, dopamine and ascorbic acid do not interfere in the determination of H2O2.The biosensor was applied to the determination of H2O2 in commercial contact lens care solutions. Good accuracy and recovery parameters were obtained.

Correlation of electrochemical properties of expanded pyridinium compounds with their single molecule conductance

A series of four expanded pyridinium molecules were used to investigate the correlation between a single molecule conductance (electron transport) and redox (electron transfer) properties at the electrode|electrolyte interface. Quantum chemical calculations of the transmission functions using DFT and non-equilibrium Green's function approach confirmed LUMO‒mediated electron transport in the break junction experiment. Single molecule conductance data can be rationalized within the framework of the non‒resonant tunneling mechanism. More interestingly, a linear correlation was found between the conductance values and the apparent electron transfer rate constants for three molecules of this series.

Effect of Carbon Nanotubes on Direct Electron Transfer and Electrocatalytic Activity of Immobilized Glucose Oxidase.

Carbon nanotubes (CNTs) are excellent supports for electrocatalysts because of their large surface area, excellent electronic conductivity, and high chemical and structural stability. In the present study, the activity of CNTs on direct electron transfer (DET) and on immobilized glucose oxidase (GOX) is studied as a function of number of walls of CNTs. The results indicate that the GOX immobilized by the CNTs maintains its electrocatalytic activity toward glucose; however, the DET and electrocatalytic activity of GOX depend strongly on the number of inner tubes of CNTs. The GOX immobilized on triple-walled CNTs (TWNTs) has the highest electron-transfer rate constant, 1.22 s–1, for DET, the highest sensitivity toward glucose detection, 66.11 ± 5.06 μA mM–1 cm–2, and the lowest apparent Michaelis–Menten constant, 6.53 ± 0.58 mM, as compared to GOX immobilized on single-walled and multiwalled CNTs. The promotion effect of CNTs on the GOX electrocatalytic activity and DET is most likely due to the electron-tunneling effect between the outer wall and inner tubes of TWNTs. The results of this study have general implications for the fundamental understanding of the role of CNT supports in DET processes and can be used for the better design of more effective electrocatalysts for biological processes including biofuel cells and biosensors.

Study of electrooxidation and enhanced voltammetric determination of β-blocker pindolol using a boron-doped diamond electrode

Pindolol (PND), an antihypertensive agent indicated for patients in the treatment of angina, hypertension, cardiac arrhythmias and recently consumed as doping agent by athletes, is electrochemically determined in this research by using a cathodically pretreated boron-doped diamond (CPT-BDD) electrode. The electrochemical response of PND studied via cyclic voltammetry on the BDD surface, shows an irreversible oxidation process. From cyclic voltammetric assays carried out at different potential scan rates, the electrochemical parameters number of electrons transferred and the apparent heterogeneous electron transfer rate constant (k0app) were determined. Additionally, chronoamperometric measurements performed at different PND concentration levels yielded the apparent diffusion coefficient of this molecule (Dapp) in 0.2 mol L−1 phosphate buffer solution (pH = 6.0). After a number of optimization steps, a differential pulse voltammetric (DPV) procedure for the sensitive determination of PND using the CPT-BDD electrode was developed. Under the optimum experimental conditions, the obtained analytical curve was linear in the wide concentration range from 0.04 to 10.0 μmol L−1 and a limit of detection of 26 nmol L−1 was also determined. The viability of the proposed voltammetric procedure was checked out towards the quantification of PND in pharmaceutical formulation samples and biological fluids. The successfully application of the proposed voltammetric procedure suggest the potentiality of this approach for field applications, such as control of pharmaceutics and monitoring of PND in biological samples from athletes subjected to anti-doping exams.

Solvent effect on the electrochemical oxidation of N,N,N′,N′-tetramethyl-1,4-phenylenediamine. New insights into the correlation of electron transfer kinetics with dynamic solvent effects

Electrochemical oxidation of N,N,N′,N′-tetramethyl-1,4-phenylenediamine (TMPD) to its cation radical (TMPD•+) and dication (TMPD++) in various nonaqueous solvents was studied using the cyclic voltammetry technique on a glassy carbon electrode. The variation of the half-wave potentials (E1/2) with the physical properties of the solvents was interpreted using multi-parametric correlation. It is shown that polarity-polarizability index, viscosity and longitudinal relaxation of solvents play an undeniable role in the E1/2 value. The electron transfer rate constants were simulated and analyzed using the MLR regression method to separate the effect of longitudinal relaxation time from other effective parameters according to the Marcus theory. Finally, a new correlation method was developed which involve solvent's Pekar factor, longitudinal and Debye relaxation time, viscosity and relative permittivity. The computational method was used for calculating the standard of the Gibbs free energy of solvation and oxidation process.

Electron transfer in an acidophilic bacterium: interaction between a diheme cytochrome and a cupredoxin.

Acidithiobacillus ferrooxidans, a chemolithoautotrophic Gram-negative bacterium, has a remarkable ability to obtain energy from ferrous iron oxidation at pH 2. Several metalloproteins have been described as being involved in this respiratory chain coupling iron oxidation with oxygen reduction. However, their properties and physiological functions remain largely unknown, preventing a clear understanding of the global mechanism. In this work, we focus on two metalloproteins of this respiratory pathway, a diheme cytochrome c4 (Cyt c4) and a green copper protein (AcoP) of unknown function. We first demonstrate the formation of a complex between these two purified proteins, which allows homogeneous intermolecular electron-transfer in solution. We then mimic the physiological interaction between the two partners by replacing one at a time with electrodes displaying different chemical functionalities. From the electrochemical behavior of individual proteins, we show that, while electron transfer on AcoP requires weak electrostatic interaction, electron transfer on Cyt c4 tolerates different charge and hydrophobicity conditions, suggesting a pivotal role of this protein in the metabolic chain. The electrochemical study of the proteins incubated together demonstrates an intermolecular electron transfer involving the protein complex, in which AcoP is reduced through the high potential heme of Cyt c4. Modelling of the electrochemical signals at different scan rates allows us to estimate the rate constant of this intermolecular electron transfer in the range of a few s-1. Possible routes for electron transfer in the acidophilic bacterium are deduced.

Comparative analysis of oxidative mechanisms of phloroglucinol and dieckol by electrochemical, spectroscopic, cellular and computational methods.

Numerous studies have been carried out on the redox activities of phenolic compounds from terrestrial plants, however, the redox pathway of phlorotannins, a type of marine algae-derived polyphenol, is far from clear. In the present study, the redox mechanisms of two phlorotannins, phloroglucinol (PL) and dieckol (DL), were comparatively scrutinized. Differential pulse voltammetry was conducted in the pH range 2.0–12.0 to determine the acid–base dissociation constant (pKa) and the number of electrons and protons involved in the redox reactions of two phlorotannins. Cyclic voltammetry was applied to obtain the heterogeneous electron transfer rate constant (k0). By means of computational calculation, UV-vis spectroscopy, and electrochemical analysis, it is proposed that PL oxidation in the whole pH range undergoes two steps which are dominated by proton-coupled electron transfer (PCET) (pH ≤ 9) and sequential proton-loss electron transfer (SPLET) mechanisms (pH > 9), respectively. In contrast, the multiple steps taking place in the DL oxidation process rely on PCET (pH ≤ 5), mixed SPLET/PCET (5 < pH ≤ 10), and electron transfer (pH > 10) mechanisms, respectively. Also, the lower proton affinity and ionization potential values of DL, which are attributed to its conjugated Cπ–O–Cπ moieties, lead to relatively higher redox activity as compared to PL in various chemical and cellular models. These findings may provide useful insights into the oxidative conversion of phlorotannins in their biological and chemical processes.

The photo-physical study of the interaction of riboflavin with Nicotine in bicontinuous microemulsion

Steady-state fluorescence spectroscopy was used to study the interaction of riboflavin with nicotine in a bicontinuous microemulsion system made up of 42.11:13.70:21.34:22.85 % w/w of water: oil: surfactant: cosurfactant. The surfactant used is cetyltrimethylammonium bromide (CTAB), the oil is tetradecane and the cosurfactant is 1-pentanol. It is observed that the interaction of riboflavin and nicotine in the prepared microemulsion lead to the quenching of riboflavin fluorescence. The bimolecular quenching rate constant, kq, of riboflavin by nicotine was observed as 4.15 x 109 M-1 s -1 with an efficiency of 56 %. The mechanism of the reaction is proposed to be diffusion limited in an activated electron transfer reaction in a solvent separated (outer-sphere) scheme. The electron transfer rate constant, kET, was calculated as 5.89 x 109 s -1 with an activation rate constant, ka, of 9.52 x 109 s -1 . The calculated solvent reorganization energy, λs, of the reaction was 1.09 eV, the free energy of interaction, ΔGo , is -2.9 eV and the free energy of activation, ΔG*, was calculated as 0.75 eV.

Role of Surface-Capping Ligands in Photoexcited Electron Transfer between CdS Nanorods and [FeFe] Hydrogenase and the Subsequent H2 Generation

Complexes of CdS nanorods and [FeFe] hydrogenase I from Clostridium acetobutylicum have been shown to photochemically produce H2. This study examines the role of the ligands that passivate the nanocrystal surfaces in the electron transfer from photoexcited CdS to hydrogenase and the H2 generation that follows. We functionalized CdS nanorods with a series of mercaptocarboxylate surface-capping ligands of varying lengths and measured their photoexcited electron relaxation by transient absorption (TA) spectroscopy before and after hydrogenase adsorption. Rate constants for electron transfer from the nanocrystals to the enzyme, extracted by modeling of TA kinetics, decrease exponentially with ligand length, suggesting that the ligand layer acts as a barrier to charge transfer and controls the degree of electronic coupling. Relative light-driven H2 production efficiencies follow the relative quantum efficiencies of electron transfer, revealing the critical role of surface-capping ligands in determining the pho...

An approach for electrochemical functionalization of carbon nanotubes/1-amino-9,10-anthraquinone electrode with catechol derivatives for the development of NADH sensors

A new type of modified electrode, consisting of electro generated quinone redox mediator and carbon nanotubes (CNT) for electrocatalytic oxidation of reduced form of β-nicotinamide adenine dinucleotide (NADH) has been developed. The CNT functionalized with 1-amino-9,10-anthraquinone electrodes (GC/CNT/AAQ) were subjected to cyclic voltammetry in the presence of selected 1,2-dihydroxybenzene derivatives (catechol, 3-methoxycatechol and 4-methylcatechol). As a result, the electroactive quinone adducts were synthesized directly on the electrode surface via Michael addition mechanism. The structures of novel compounds were established using complementary computational studies and then were confirmed by HPLC-ESI-MS method. Electrochemical characterization of the electrodes after modification was carried out by cyclic voltammetry in broad range of pH. The heterogeneous electron transfer rate constants (ks) for the studied quinone modified electrodes were estimated and the obtained values (between 9.8 and 16.7 s−1) suggest moderate electron transfer kinetics. The electrodes displayed remarkable catalytic activity toward NADH oxidation in neutral phosphate buffer (pH = 7.4). The incorporation of quinone moieties onto electrode surface resulted in significantly decreased oxidation potential and enhanced current as compared to unmodified electrodes. NADH has been successfully determined at 0.1 V vs. Ag/AgCl, on all developed electrodes. The established method is characterized by linearity, low limits of detection (from 0.63 to 1.15 μM) and quantitation (from 1.9 to 3.47 μM), high sensitivity, suitable accuracy, repeatability and precision.

Electrochemistry of Metalloproteins Attached through Functional Self-Assembled Monolayers on Gold and Ferromagnetic Electrodes.

We report the experimental results of a study of the electron-transfer processes of redox-active metalloproteins bound to mixed self-assembled monolayers (SAMs) on magnetic (nickel or ultrathin gold-coated nickel) or nonmagnetic (gold) electrodes. Metalloproteins, such as hemoglobin (Hb), Cytochrome C (Cyt C), and Cyt C oxidase, are attached through electrostatic interactions to the free carboxylate or imidazole groups present in the mixed SAMs. The formation of both mixed SAMs and SAM/metalloprotein heterostructures were confirmed by using advanced surface analysis techniques, such as polarization modulation infrared reflection absorption spectroscopy and aqueous contact angle measurements. Electrochemical measurements indicated a stronger electronic coupling between Hb and Cyt C oxidase and the mixed-SAM-coated gold or gold-coated-nickel electrodes, whereas a weaker coupling was found between the protein and the pure nickel electrode. Surface coverage and the electron-transfer rate constant were estimated from the cyclic voltammetry data.

Ultraflat, Pristine, and Robust Carbon Electrode for Fast Electron-Transfer Kinetics.

Electron-beam (e-beam) deposition of carbon on a gold substrate yields a very flat (0.43 nm of root-mean-square roughness), amorphous carbon film consisting of a mixture of sp2- and sp3-hybridized carbon with sufficient conductivity to avoid ohmic potential error. E-beam carbon (eC) has attractive properties for conventional electrochemistry, including low background current and sufficient transparency for optical spectroscopy. A layer of KCl deposited by e-beam to the eC surface without breaking vacuum protects the surface from the environment after fabrication until dissolved by an ultrapure electrolyte solution. Nanogap voltammetry using scanning electrochemical microscopy (SECM) permits measurement of heterogeneous standard electron-transfer rate constants (k°) in a clean environment without exposure of the electrode surface to ambient air. The ultraflat eC surface permitted nanogap voltammetry with very thin electrode-to-substrate gaps, thus increasing the diffusion limit for k° measurement to >14 cm/s for a gap of 44 nm. Ferrocene trimethylammonium as the redox mediator exhibited a diffusion-limited k° for the previously KCl-protected eC surface, while k° was 1.45 cm/s for unprotected eC. The k° for Ru(NH3)63+/2+ increased from 1.7 cm/s for unprotected eC to above the measurable limit of 6.9 cm/s for a KCl-protected eC electrode.

Improved peroxide biosensor based on Horseradish Peroxidase/Carbon Nanotube on a thiol-modified gold electrode.

A new 3-dimensional (3D) network of crosslinked Horseradish Peroxidase/Carbon Nanotube (HRP/CNT) on a thiol-modified Au surface has been described in order to build up the effective electrical wiring of the enzyme units with the electrode. The synthesized 3D HRP/CNT network has been characterized with cyclic voltammetry and amperometry which results the establishment of direct electron transfer between the redox active unit of HRP and the Au surface. Electrochemical measurements reveal that the high biological activity and stability is exhibited by the immobilized HRP and a quasi-reversible redox peak of the redox centre of HRP was observed at about -0.355 and -0.275V vs. Ag/AgCl. The electron transfer rate constant, KS and electron transfer co-efficient α were found as 0.57s-1 and 0.42, respectively. Excellent electrocatalytic activity for the reduction of H2O2 was exhibited by the developed biosensor. The proposed biosensor modified with HRP/CNT 3D network displays a broader linear range and a lower detection limit for H2O2 determination. The linear range is from 1.0×10-7 to 1.2×10-4M with a detection limit of 2.2.0×10-8M at 3σ. The Michaelies-Menten constant Kapp M value is estimated to be 0.19mM. Moreover, this biosensor exhibits very high sensitivity, good reproducibility and long-time stability.

Collision Dynamics during the Electrooxidation of Individual Silver Nanoparticles.

Recent high-bandwidth recordings of the oxidation and dissolution of 35 nm radius Ag nanoparticles at a Au microelectrode show that these nanoparticles undergo multiple collisions with the electrode, generating multiple electrochemical current peaks. In the time interval between observed current peaks, the nanoparticles diffuse in the solution near the electrolyte/electrode interface. Here, we demonstrate that simulations of random nanoparticle motion, coupled with electrochemical kinetic parameters, quantitatively reproduce the experimentally observed multicurrent peak behavior. Simulations of particle diffusion are based on the nanoparticle-mass-based thermal nanoparticle velocity and the Einstein diffusion relations, while the electron-transfer rate is informed by the literature exchange current density for the Ag/Ag+ redox system. Simulations indicate that tens to thousands of particle-electrode collisions, each lasting ∼6 ns or less (currently unobservable on accessible experimental time scales), contribute to each experimentally observed current peak. The simulation provides a means to estimate the instantaneous current density during a collision (∼500-1000 A/cm2), from which we estimate a rate constant between ∼5 and 10 cm/s for the electron transfer between Ag nanoparticles and the Au electrode. This extracted rate constant is approximately equal to the thermal collisional velocity of the Ag nanoparticle (4.6 cm/s), the latter defining the theoretical upper limit of the electron-transfer rate constant. Our results suggest that only ∼1% of the surface atoms on the Ag nanoparticles are oxidized per instantaneous collision. The combined simulated and experimental results underscore the roles of Brownian motion and collision frequency in the interpretation of heterogeneous electron-transfer reactions involving nanoparticles.

Electrochemical evaluation of catalytic effect of silver in reducing 4-nitroaniline: Analytical application

The present work reports on electrocatalytic activity of silver electrode for 4-nitroaniline (4-NA) reduction, where its performance is compared with conventionally used electrodes (gold, graphite and glassy carbon). The voltammetric behavior of 4-nitroaniline (4-NA) is explored where a sensitive cathodic peak has appeared at about −0.26V (vs. Ag/AgCl/3M KCl) in Britton Robinson buffer solution (pH2.0). This peak results from the irreversible reduction of 4-NA at metallic silver electrode. The catalytic effect was evaluated using cyclic voltammetry and chronoamperometry. Indeed, the cathodic transfer coefficient was 0.57 and electron transfer rate constant was evaluated to be 7.38×10−5cm2s−1. Electrochemical impedance spectroscopy also confirms our experimental results as the silver electrode shows least charge transfer resistance. In order to provide electrochemical detection to reducing the nitro groups of 4-NA on the silver electrode surface, the differential pulse voltammograms were used in the potential range between 0.2V and −1V vs. Ag/AgCl/(sat. KCl).Furthermore, silver electrode can be used successfully to improve the detection of 4-NA at very low concentration levels with high sensitivity. The linear calibration range was from 8.0×10−9 to 1.0×10−3molL−1. The limit of detection (LOD) was found to be 4.74×10−9molL−1, while relative standard deviation (RSD) at 1.0×10−4molL−1 4-NA concentration was 1.94% for eight repetitions. Then, the proposed method was applied to detect 4-NA in wastewater and drinking water with satisfactory results.

Fructose Dehydrogenase Electron Transfer Pathway in Bioelectrocatalytic Reactions

AbstractWe present kinetic and mechanistic studies of fructose oxidation by fructose dehydrogenase (FDH) using the electrochemical methods of stationary and rotating disk voltammetry. FDH was physically adsorbed on unmodified multiwalled carbon nanotubes (MWCNT) to study direct electron transfer (DET) parameters, and for comparison an MWCNT with an adsorbed pyrene derivative of naphthoquinone employed as the mediator in mediated electron transfer, MET, was also examined. Kinetic parameters, such as the number of electrons transferred, the turnover number, and the electron transfer rate constant, were calculated. Comparison of the non‐turnover and catalytic behaviour revealed the role of the heme c active site in the electron transfer of FDH. It was also shown that a mediator with a sufficiently low formal potential, such as the naphthoquinone, substitutes for the heme c site in the electron transfer to the electrode. The kinetic parameters of the processes proved that the application of the mediator results in an increase in the rate of fructose catalytic oxidation compared to that of the DET oxidation process.