Catalytic Reduction Of Hydrogen Peroxide Research Articles

Catalytic reduction of oxygen and hydrogen peroxide by nanoporous gold

Nanoporous gold (NPG) made by dealloying silver/gold alloys is a mesoporous metal combining high surface area and high conductivity. Recently, NPG has been shown to exhibit some of the high catalytic activity previously associated only with supported gold nanoparticles. Here we describe how NPG acts as a catalyst for the oxygen reduction reaction in both gas phase (in fuel cells) and aqueous environments (using rotating disk electrochemistry). NPG was found to reduce oxygen via an effectively 4-four electron route comprised of a first reduction of oxygen to hydrogen peroxide, and then an unusually active further catalytic reduction of hydrogen peroxide to water.

Catalytic reduction of hydrogen peroxide at metal hexacyanoferrate composite electrodes and applications in enzymatic analysis

The electrocatalytic activity of various metal hexacyanoferrates (M hcfs) (i) immobilized on graphite electrodes, and (ii) as components of a composite electrode was investigated with respect to the reduction of hydrogen peroxide. The flow-through working electrode was a thin layer consisting of a composite of M hcf, graphite, and polymethylmetacrylate (PMMA) as a binder, sandwiched between two Plexiglas plates. Among the pure M hcfs immobilized on a graphite electrode, iron(III) hexacyanoferrate (Prussian blue) exhibits the highest electrocatalytic effect, whereas in the composite electrodes chromium(III) hexacyanoferrate (Cr hcf) shows the highest activity and best performance and reproducibility for the electrochemical reduction of H 2O 2. The Cr hcf electrode provides a linear dependence on H 2O 2 concentration in the range 2.5 × 10 −6 mol L −1 (LOD) to 1 × 10 −4 mol L −1 (phosphate buffer, pH 7). The sensor was applied for the detection of H 2O 2 enzymatically produced by glucose oxidase. The optimal conditions for the peroxide injection were 2 min after the beginning of the reaction and 25 °C with a detection limit of 7.0 × 10 −6 mol L −1 for glucose.

Direct electrochemistry and electrocatalysis of heme-proteins entrapped in agarose hydrogel films

Three heme-proteins, including myoglobin (Mb), hemoglobin (Hb) and horseradish peroxidase (HRP), were immobilized on edge-plane pyrolytic graphite (EPG) electrodes by agarose hydrogel. The proteins entrapped in the agarose film undergo fast direct electron transfer reactions, corresponding to Fe III+e −→Fe II. The formal potential ( E°′), the apparent coverage ( Γ), the electron transfer coefficient ( α) and the apparent electron transfer rate constant ( k s) were calculated by integrating cyclic voltammograms or performing nonlinear regression analysis of square wave voltammetric (SWV) experimental data. The E°′s are linearly dependent on solution pH (redox Bohr effect), indicating that the electron transfer was proton-coupled. Ultraviolet visible (UV-Vis) and reflection–absorption infrared (RAIR) spectra suggest that the conformation of proteins in the agarose film are little different from that proteins alone, and the conformation changes reversibly in the range of pH 3.0–10.0. Atomic force microscopy (AFM) images of the agarose film indicate a stable and crystal-like structure formed possibly due to the synergistic interaction of hydrogen bonding between N, N-dimethylformamide (DMF), agarose hydrogel and heme-proteins. This suggests a strong interaction between the heme-proteins and the agarose hydrogel. DMF plays an important role in immobilizing proteins and enhancing electron transfer between proteins and electrodes. The mechanisms for catalytic reduction of hydrogen peroxide and nitric oxide (NO) by proteins entrapped in agarose hydrogel were also explored.

Glucose Biosensors Based on Carbon Nanotube Nanoelectrode Ensembles

This paper describes the development of glucose biosensors based on carbon nanotube (CNT) nanoelectrode ensembles (NEEs) for the selective detection of glucose. Glucose oxidase was covalently immobilized on CNT NEEs via carbodiimide chemistry by forming amide linkages between their amine residues and carboxylic acid groups on the CNT tips. The catalytic reduction of hydrogen peroxide liberated from the enzymatic reaction of glucose oxidase upon the glucose and oxygen on CNT NEEs leads to the selective detection of glucose. The biosensor effectively performs a selective electrochemical analysis of glucose in the presence of common interferents (e.g., acetaminophen, uric and ascorbic acids), avoiding the generation of an overlapping signal from such interferers. Such an operation eliminates the need for permselective membrane barriers or artificial electron mediators, thus greatly simplifying the sensor design and fabrication.

Wiring of enzymes to electrodes by ultrathin conductive polyion underlayers: enhanced catalytic response to hydrogen peroxide.

Stable electroactive films were grown layer by layer on rough pyrolytic graphite electrodes featuring 4-nm underlayers of sulfonated polyaniline (SPAN) covered with a film containing myoglobin or horseradish peroxidase grown in alternating layers with poly(styrenesulfonate). The self-doped polyanionic SPAN layer, grown on a 2-nm polycation layer, was conductive between about 0.1 and -0.4 V vs SCE at pH 4.5. The enzyme films had the architecture PDDA/SPAN/(enzyme/PSS)3, where PDDA is poly(diallyldimethylammonium) ion. Comparisons of voltammetric measurements of electroactive protein with quartz crystal microbalance measurements of total protein showed that 90% or more of the protein was coupled to the electrode when the SPAN underlayer was present, as opposed to approximately 40% protein electroactivity when SPAN was absent. As a consequence of the highly efficient coupling between enzymes and electrode, the PDDA/SPAN/(enzyme/PSS)3 films exhibited a higher sensitivity for the electrochemical catalytic reduction of hydrogen peroxide. Amperometry at a rotating disk electrode at 0 V gave sensitivity for hydrogen peroxide up to 14 microA microM(-1) cm(-2) in the submicromolar concentration range and a detection limit of approximately 3 nM. Results suggest the future utility of ultrathin layers of conductive self-doping polyions in improving sensitivity of enzyme biosensors.

Electrochemical catalysis with redox polymer and polyion–protein films

Supramolecular redox-active assemblies on electrodes are of fundamental interest and can be used to create functioning devices such as sensors, biosensors, and bioreactors. The ability of redox-active films to mediate electron transfer reactions in 3-D dramatically increases the sensitivity with which target molecules can be determined. Metallopolyion hydrogel films immobilized on electrode surfaces exhibit many properties that are reminiscent of those shown by redox-active proteins. This review discusses the electrochemical properties and applications of such films, including mediating electron transfer between electrodes and oxidase enzymes. In addition, polyion–protein films grown layer by layer have certain advantages in device fabrication, including facilitating direct electron transfer for many proteins, mechanical stability, use of tiny amounts of protein, and control of film architecture. This review presents examples of iron heme proteins in films grown layer by layer by alternate electrostatic adsorption for catalytic reduction of hydrogen peroxide and trichloroacetic acid and for oxidation of styrene.

A Role for Rubredoxin in Oxidative Stress Protection in Desulfovibrio vulgaris: Catalytic Electron Transfer to Rubrerythrin and Two-Iron Superoxide Reductase

Desulfovibrio vulgaris rubredoxin, which contains a single [Fe(SCys)4] site, is shown to be a catalytically competent electron donor to two enzymes from the same organism, namely, rubrerythrin and two-iron superoxide reductase (a.k.a. rubredoxin oxidoreductase or desulfoferrodoxin). These two enzymes have been implicated in catalytic reduction of hydrogen peroxide and superoxide, respectively, during periods of oxidative stress in D. vulgaris, but their proximal electron donors had not been characterized. We further demonstrate the incorrectness of a previous report that rubredoxin is not an electron donor to the superoxide reductase and describe convenient assays for demonstrating the catalytic competence of all three proteins in their respective functions. Rubrerythrin is shown to be an efficient rubredoxin peroxidase in which the rubedoxin:hydrogen peroxide redox stoichiometry is 2:1 mol:mol. Using spinach ferredoxin-NADP+ oxidoreductase (FNR) as an artificial, but proficient, NADPH:rubredoxin reductase, rubredoxin was further found to catalyze rapid and complete reduction of all Fe3+ to Fe2+ in rubrerythrin by NADPH under anaerobic conditions. The combined system, FNR/rubredoxin/rubrerythrin, was shown to function as a catalytically competent NADPH peroxidase. Another small rubredoxin-like D. vulgaris protein, Rdl, could not substitute for rubredoxin as a peroxidase substrate of rubrerythrin. Similarly, D. vulgaris rubredoxin was demonstrated to efficiently catalyze reduction of D. vulgaris two-iron superoxide reductase and, when combined with FNR, to function as an NADPH:superoxide oxidoreductase. We suggest that, during periods of oxidative stress, rubredoxin could divert electron flow from the electron transport chain of D. vulgaris to rubrerythrin and superoxide reductase, thereby simultaneously protecting autoxidizable redox enzymes and lowering intracellular hydrogen peroxide and superoxide levels.

Sol-gel-derived prussian blue-silicate amperometric glucose biosensor.

A new type of inorganic biosensor is introduced. The sensor comprises glucose oxidase enzymes encapsulated in a sol-gel-derived Prussian blue-silicate hybrid network. Glucose is detected by the biocatalytic reduction of oxygen followed by catalytic reduction of hydrogen peroxide by the Prussian blue catalyst. The sol-gel silicate entails a rigid encapsulating matrix, the Prussian blue provides chemical catalysis and charge mediation from the reduction site to the supporting electrode, and the enzyme is responsible for the biocatalysis. The feasibility of a dual optical/electrochemical mode of analysis is also demonstrated.

A phenazine methosulphate-mediated sensor sensitive to lactate based on entrapment of lactate oxidase and horseradish peroxidase in composite membrane of poly(vinyl alcohol) and regenerated silk fibroin

An amperometric phenazine methosulphate-mediated sensor sensitive to lactate was fabricated, which was based on immobilization of lactate oxidase and horseradish peroxidase in a novel composite membrane of poly(vinyl alcohol) and regenerated silk fibroin. The water absorbability and mechanical properties of the composite membrane were investigated. Horseradish peroxidase (HRP) was employed in the catalytic reduction of hydrogen peroxide, formed by the lactate oxidase reaction, to amplify the amperometric response of the lactate sensor. In this bienzyme configuration, phenazine methosulphate was used as an electron transfer mediator between immobilized HRP and a glassy carbon electrode. Effects of pH, temperature, applied potential and concentration of phenazine methosulphate on the steady-state bioelectrocatalytic oxidation of lactate at the sensor were evaluated. Dependence of Michaelis-Menten constant K m app on the concentration of phenazine methosulphate and applied potential was also investigated. The response of the sensor to lactate reached 95% steady-state current within 20 s.

Electrocatalytic reduction of hydrogen peroxide on a palladium‐modified carbon paste electrode

AbstractA palladium‐dispersed carbon paste electrode was used for the electrocatalytic reduction of hydrogen peroxide. After cycling the potential between 0.4 and −0.8V (vs. SCE) in pure dilute alkaline solution (10−3M NaOH), the resulting electrode surface exhibited stable and sensitive electrocatalytic response for hydrogen peroxide. The involved catalytic mechanism was thoroughly investigated. The electrocatalytic effect was attributed to electrogenerated elemental palladium at the electrode surface. The catalytic reduction of hydrogen peroxide proceeds via the hydroxyl radical, OH·. Dissolved oxygen can also be catalytically reduced in a similar way to hydrogen peroxide. The height of the cathodic catalytic current peak, as obtained by linear sweep voltammetry (LSV) was directly proportional to the hydrogen peroxide concentration over a very wide concentration range (0.1–600mgL−1). The detection limit (3σ) was calculated as 50 μgL−1 H2O2.

Sustained oscillations during catalytic reduction of hydrogen peroxide on copper‐iron‐sulfide electrodes II

AbstractInvestigations on the reduction of H2O2 on copper‐iron‐sulfides, which were initiated with Cu5FeS4, are extended to cuprous sulfide (Cu2S). This system is also characterized by pronounced sustained electrochemical oscillations which appear during the reduction of H2O2. They are qualitatively analog to that observed with Cu5FeS4 and can be described by the same differential equation of the Lotka Volterra type. The three dimensional phase surface of the derived differential equation is computer drawn, and the nature of the observed frequency instability of oscillations explained. In order to confirm the proposed participation of metal, metal hydroxide and metal oxide‐surface sites in the oscillation mechanism, several experimental tests were theoretically evaluated and experimentally verified.Oscillations can be stopped with a metal chelating agent (EDTA) or with a strongly alkaline electrolyte and the sulfide surface stabilized into either one of the two possible states (hydroxide covered and hydroxide deficient) between which otherwise oscillations occur. Light which is destroying oxide bonds on the sulfide surface by a photo electrochemical mechanism, can be used to modulate frequency and amplitude of electrochemical oscillations. Experimental evidence for the constancy of entropy production during oscillations, which is a very specific property of Lotka‐Volterra‐systems, is also provided.It is concluded that oscillations of the Lotka Volterra type actually exist. They are, however, easily perturbated by chemical side reactions to give either limit cycle oscillations or damped or undamped oscillations.

Sustained oscillations during catalytic reduction of hydrogen peroxide on copper‐iron‐sulfide electrodes I

AbstractThe reduction of hydrogen peroxide, the decomposition of which is catalized by iron and copper, is studied at copper‐iron‐sulfide electrodes. Pronounced electrochemical oscillations with frequencies up to several cycles per second are observed with Cu5FeS4 in a potential range between −0.3 and −0.9 V. They have a rise time of approximately 1 ms, a decay time of the order of several hundred ms and appear both under potentiostatic and galvanostatic conditions. The entire electrode/electrolyte interface is participating in these oscillations. The signal which is synchronizing the oscillations is propagating with a velocity of approximately 10 m/s over the sulfide surface. Experimental evidence for the participation of metal‐hydroxide, metal and metal‐oxide surface states in these oscillations is provided and two autocatalytic reactions are derived which involve the O2H radical as a reactant. They correspond to mechanisms in which catalytic sites have to exist close to reaction sites for the reaction to proceed. Two kinetical differential equations of the Lotka‐Volterra type are obtained which are known to describe sustained oscillations. Their oscillation frequency is, in agreement with experimental observations, not uniquely defined by the reactants but dependent on the initial and boundary conditions of the system.