Rotating-ring-disk analysis of iron tetra(N-methylpyridyl)porphyrin in electrocatalysis of oxygen

Abstract

Future efforts involving the technique presented here will involve improvement of resolution using a smaller slit, improvement in alignment between slit and electrode, and the use of diffracted light to examine events close to the electrode. In its present form, the technique allows direct observation of concentrations of electroactive materials as a function of both time and distance with unprecedented sensitivity and selectivity. The long pathlength, selectivity gained from wavelength selection, and spatial resolution will allow much greater definition of the solution adjacent to an electrode surface. In addition to observing fundamental aspects of electrochemical mass transport, the technique will allow improved characterization of homogeneous reactions accompanying charge transfer. ACKNOWLEDGMENTThe authors thank Robert Fagan for helpful discussion. LITERATURE CITED(1) Winograd, N.; Kuwana, T. "Spectroetectrochemlstry at Optically Transparent

Direct observation of intermediates formed during steady-state electrocatalytic O 2 reduction by iron porphyrins

“…6 C and D). In particular, the 830-cm −1 band, which gains intensity in 16 O 2 buffer (Fig. 6 A and C), loses intensity in the 18 O 2 -saturated buffer (Fig.…”

“…Both natural systems [metalloenzymes such as cytochrome c oxidase (CcO), hydrogenase, and glucose oxidase] and biomimetic systems (i.e., synthetic/biochemical mimics of the natural enzyme) are known to function as electrocatalysts (12)(13)(14)(15). In particular, it has been known for five decades that heme/porphyrin-based electrocatalysts (both natural and synthetic) catalyze electrochemical O 2 , H + , and CO 2 reduction (14,(16)(17)(18)(19). Several excellent metalloporphyrin-based O 2 reduction electrocatalysts have been reported, some mimicking natural active sites and some inspired by their design (14,20).…”

Oxygen Reduction on Transition‐Metal Porphyrins in Acid Electrolyte I. Activity

“…dissociation 1501, or dismutation [51] of adsorbed 0,H). It has been found that in many, though not all, cases 0, reduction is associated with the (presumably) Me"/Me"' redox transition in the adsorbed or attached chelate [49,[52][53][54][55][56][57][58][59]. Unfortunately it has not been possible to study the Me"/Me"l redox process in our catalysts by cyclic voltammetry or differential pulse polarography owing to the high background currents of the active carbon support.…”

An overview of the electrochemical reduction of oxygen at carbon-based modified electrodes

“…The oxygen reduction reaction with metalloporphyrins as electrocatalysts has been extensively studied [116][117][118][119][120][121][122][123]. It was shown that porphyrins have high electrocatalytic activity toward the ORR.…”

“…two for all four CoPPx and therefore it was concluded that on glassy carbon electrodes modified with CoPPx, the oxygen reduction reaction proceeds through two-electron process to hydrogen peroxide. Also, the electrogenerated ferrous form of iron tetrakis (M-methyl-4-pyridyl) porphyrin (bisulfate) has been shown to be an effective catalyst for the reduction of oxygen to hydrogen peroxide via two-electron pathway [117][118][119]127]. On the other hand, the reduced form of iron tetrakis (M-methyl-4-pyridyl) porphyrin, electrogenerated at a highly polished glassy carbon electrode has showed catalytic activity for electrochemical reduction of oxygen to water via a multistep mechanism [116].…”