Detection of Hydrogen Peroxide Produced during the Oxygen Reduction Reaction at Self-Assembled Thiol−Porphyrin Monolayers on Gold using SECM and Nanoelectrodes

Abstract

Porphyrin molecules were immobilized on polycrystalline gold and glassy carbon by coordinating cobalt(II) 5,10,15,20-tetraphenyl-21H,23H-porphine to a 4-aminothiophenol self-assembled monolayer. The resulting electrocatalytic activity of the metalloporphyrin-modified substrates with regard to the oxygen reduction reaction was characterized by means of cyclic voltammetry and scanning electrochemical microscopy (SECM) using nanoelectrodes of well-defined geometry. From substrate generation tip collection (SG-TC) mode SECM measurements performed under steady-state conditions and at different applied substrate potentials, it is possible to extract kinetic information relevant to electrocatalyst substrates such as metalloporphyrin-modified gold and glassy-carbon electrodes. Such an approach allows for the isolation of the unique contribution of the electrocatalyst to the oxygen reduction reaction and peroxide formation.

Porphyrins as Active Components for Electrochemical and Photoelectrochemical Devices

“…19 Cobalt porphyrins are, in general, the most commonly investigated also for chemisorbed monolayers and retain the above-mentioned aptitude to undertake a two-electron reduction pathway. [155][156][157] Combined spectroelectrochemical and optical voltammetry experiments concluded that the electrocatalysis begins at potentials corresponding to the formation of the Co(II) species within the monolayer. 158 A similar trend to that observed by Itaya and coworkers 17 was found for SAMs composed of Co(II) and Fe(III) complexes of a disulfide porphyrin.…”

Study of Porosity-Dependent Oxygen Reduction at Porous Platinum Tips Using Scanning Electrochemical Microscopy

“…22 The substrate generation/tip collection (SG-TC) mode of SECM has been widely utilized for the investigation of ORR activity at metallic thin films. 15,17,19 The SG-TC mode of SECM, however, still shows low collection efficiency less than 50%. 23 The tip-generation/substratecollection (TG-SC) mode of SECM appears to be attractive for detecting intermediates of tip electrode reaction with nearly 100% collection efficiency.…”

“…6 Increasing ORR current density (including n value) and more positive E 1/2 were observed with increasing pore size. Due to very thin Pt film on carbon substrate, however, the catalytic activity of carbon substrate is not negligible.Rotating ring and disk electrode (RRDE) 9-11 and scanning electrochemical microscopy (SECM) [12][13][14][15][16][17][18][19][20][21] have been generally used to study the ORR activity and mechanism at various metallic thin film catalysts using Pt or Au electrodes for H 2 O 2 detection. Especially, SECM has been proven to be useful for studying the mechanism and activity associated with electrode reactions with high collection efficiency, minimizing experimental errors, such as the effects of the resistive potential drop in solution, the charging current, etc.…”

SECM screening of the catalytic activities of AuPd bimetallic patterns fabricated by electrochemical wet-stamping technique

“…SECM has been proved as a good technique for evaluating the local electrocatalytic activity of different catalysts [6][7][8] and also represents a powerful electrochemical tool for investigating heterogeneous electron-transfer (HET) reactions at interfaces between an electrode and an electrolyte [9]. For example, it has been applied in detection and quantification of H 2 O 2 [10][11][12][13], which not only is an important species in energy storage field such as intermediate of oxygen reduction reaction [14][15][16][17] but also plays an important role in clinical applications, and environmental analysis. The redox-competition mode (RC) of SECM has been applied for screening of the electrocatalysts in the reduction of H 2 O 2 by Schuhmann and co-workers [18][19][20][21][22].…”