Glassy carbon electrodes electrocatalytic reactions

If production of an oxidizing hole in the da orbital is the important factor in the photochemical reaction, then electrochemical veneration of such a hole should produce a highly reactive intermediate mat would mimic the initial step in the 3(da po) photoreaction. Several of the binuclear complexes undergo reversible one-electron oxidations in noncoordinating solvents (22-24). The complex Rh2(TMB)42+ possesses a quasireversible one-electron oxidation at 0.74 V (Electrochemical measurements for [Rh2(TMB)4](PF6)2 CH2CI2/TBAPF6 (0.1 M), glassy carbon electrode, 25°C, SSCE reference electrode). Electrochemical oxidation of Rh2(TMB)42+ in the presence of 1,4-cyclohexadiene exhibits an enhanced anodic current with loss of the cathodic wave, behavior indicative of an electrocatalytic process (25). Bulk electrolysis of Rh2(TMB)42+ in an excess of 1,4-cyclohexadiene results in the formation of benzene and two protons (Equation 4). 

The electrocatalytic effect (oxidation of NADH) observed with a glassy carbon electrode coated with polymer containing dopamine (covalently attached to a polymethyl methacrylic matrix) is analogous to bulk reactions of melanins (see Section V). The overall electrochemical behavior, however, indicates a very slow reaction involving only a few monolayers (250),... 

A simple and inexpensive cholesterol biosensor was fabricated by immobilizing cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) onto a poly (thionine) modified glassy carbon electrode (GCE/PTH) (Fig. 41) [122]. Hydroqui-none (HQ) was used as a mediator to promote the electron transfer between the enzyme and the electrode. It results in excellent electrocatalytic activity of immobilized HRP for H2O2 reduction, which was produced from cholesterol by the enzymatic reaction with ChOx. The linear range for cholesterol spanned from 25 to 125 iM, with a detection limit and a sensitivity of 6.3 pM and 0.18 pA/cm /p M, respectively. The highly reproducible and sensitive GCE/PTH/ChOx/HRP sensor exhibited an interference-free signal for cholesterol detection with excellent recoveries for real sample analysis. 

There is an abundance of potential redox catalysis applications of large clusters, aided by the ease of synthesis and fast ET kinetics. As an example, Mirkhalaf and Schiffrin i studied the electrocatalytic reduction of oxygen, which is important in the design of fuel cells, on 7 nm 4-diazoniumdecylbenzene lluoroborate-protected Au MFCs, as films on decylphenyl-coated glassy carbon electrodes. Electrons hop from the electrode surface to the nanocluster metal centers to participate in ET reactions. The choice of a hydrophobic ligand provides an apt environment for stabilization of reactive superoxide and peroxide intermediates. 

Carbons exhibit a low electrocatalytic activity for the hydrogen electrode reaction (HER). Structural characteristics have significant electrocatalytic effects on the HER as changes from 2 X 10 to 2.5 x 10 A/cm on going from the basal plane to the side face of pyrolytic graphite. On glassy carbon, the HER overpotential decreases as the pretreatment temperature is increased. This thermal treatment leads to stmctural and chemical transformations from carbonization, precrystaUization, and to graphitization. 

Salimi, A., Banks, C.E., and Compton, R.G. (2003). Ultrasonic effects on the electroreduction of oxygen at a glassy carbon anthraquinone-modified electrode. The Koutecky-Levich equation applied to insonated electrocatalytic reactions. Phys. Chem. Chem. Phys., 5, 3988-93. 

The intermittent plasma-assisted vacuum deposition technique has been found to introduce the effective electrocatalytic activity and stability for CO2 reduction into metal phthalocyanine thin films formed on a glassy carbon. The films properties are significantly influenced by the chemical state of the Aim. It has been suggested that the electrode process is determined by the surface chemical reaction involving adsorbed H and/or H+ and a carbon containing intermediate ". ... 

---