UNSPECIFIED (1998) Scanning electrochemical microscopy - Kinetics of chemical reactions following electron-transfer measured with the substrate-generation-tip-collection mode. JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 94 (6). pp. 753-759. ISSN 0956-5000

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Abstract

The substrate-generation-tip-collection (SG-TC) mode of the scanning electrochemical microscope (SECM) is used as a new approach to investigate the kinetics of EC processes. Under the conditions of interest, a species O is generated at a macroscopic substrate (generator) electrode, with potential-step control, through the diffusion-limited electrolysis of a solution species R (E step). As O diffuses away from the generator, it undergoes a first order Chemical reaction in solution (C step). A fraction of O is collected by electrolysis back to R at an externally biased ultramicroelectrode (UME), positioned directly over the substrate. This promotes the diffusional feedback of R to the substrate. Theory for the problem, relating the time-dependent tip current response to the rate constant for the C step and the tip-substrate electrode separation is developed numerically. Results of the calculations illustrate how the characteristic features of the tip current transients: peak current, peak time and post-half-peak time, depend on the kinetics of the C step and the inter-electrode separation. It is shown that both the kinetics and tip-substrate separation can be determined independently from a single transient by simply measuring the peak current and peak time. The theoretical results are validated experimentally through model studies of the oxidative deamination of N,N,-dimethyl-p-phenylenediamine(DMPPD) in aqueous solution at high pH. The effective second-order rate constant for the deamination step is in excellent agreement with values measured by alternative methods.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry Q Science > QC Physics
Journal or Publication Title:	JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
Publisher:	ROYAL SOC CHEMISTRY
ISSN:	0956-5000
Date:	21 March 1998
Volume:	94
Number:	6
Number of Pages:	7
Page Range:	pp. 753-759
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/15885

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