Rotating ring-disk electrode design

Using underpotential deposition with the redox replacement technique a novel electrochemical approach for nanoparticle-based catalyst has been designed. Here, the as-prepared Pt-coated Au nanoparticle monolayer at atomic level on the electrode surface can reduce O2 predominately by 4e to H2O, which was confirmed by rotating ring disk electrode technique (Figure 8). 

Ordinarily, the selectivity of ORR is determined by means of rotating disk electrode (RDE) or rotating ring-disk electrode (RRDE) voltammetry. The RDE is designed to boost the diffusion of an electroanalyte in conditions where an electrochemical reaction is limited by diffusion of the analyte to the electrode. In RRDE, a ring (often platinum) surrounds the disk electrode with an insulating material (usually Teflon) between them (Fig. 7.5). 

Another specialized form of voltammetry involves the use of either a rotated-disk or a ring-disk indicating electrode. With this type of electrode the current is directly proportional to the square root of the rate of rotation if it is a diffusion-controlled process. To obtain complete adherence to the square-root relationship, a hydrodynamically sound design for the electrode is essential.43 Figure 3.12 illustrates the geometric features that have been found to give reliable performance for rotation rates as high as 10,000 rpm. 

Recently, Mottola [98] reported a sensor based on the disk-ring principle previously developed by Kamin and Wilson [99], and Wang and Lin [100]. Unlike Mottola s design, its forerunners involved no stationary ring electrode or rotation of the reactor part in addition, their reactor/electrode was located at the cell bottom. In Mottola s assembly, a product of an enzyme-catalysed reaction at a bioreactor rotated at a constant speed was hydrodynamically transported to a stationary ring electrode, where it was electrochemically monitored. The sample was transported to the detection imit by an tm-... 

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