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Issue 45, 2006
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Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity

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Abstract

In order to locally analyse catalytic activity on modified surfaces a transient redox competition mode of scanning electrochemical microscopy (SECM) has been developed. In a bi-potentiostatic experiment the SECM tip competes with the sample for the very same analyte. This leads to a current decrease at the SECM tip, if it is positioned in close proximity to an active catalyst site on the surface. Specifically, local catalytic activity of a Pt-catalyst modified sample with respect to the catalytic reduction of molecular oxygen was investigated. At higher local catalytic activity the local O2 partial pressure within the gap between accurately positioned SECM tip and sample is depleted, leading to a noticeable tip current decrease over active sites. A flexible software module has been implemented into the SECM to adapt the competition conditions by proper definition of tip and sample potentials. A potential pulse profile enables the localised electrochemically induced generation of molecular oxygen prior to the competition detection. The current decay curves are recorded over the entire duration of the applied reduction pulse. Hence, a time resolved processing of the acquired current values provides movies of the local oxygen concentration against x,y-position. The SECM redox competition mode was verified with a macroscopic Pt-disk electrode as a test sample to demonstrate the feasibility of the approach. Moreover, highly dispersed electro-deposited spots of gold and platinum on glassy carbon were visualised using the redox competition mode of SECM. Catalyst spots of different nature as well as activity inhomogeneities within one spot caused by local variations in Pt-loading were visualised successfully.

Graphical abstract: Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity

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Publication details

The article was received on 04 Jul 2006, accepted on 10 Oct 2006 and first published on 23 Oct 2006


Article type: Paper
DOI: 10.1039/B609511A
Citation: Phys. Chem. Chem. Phys., 2006,8, 5359-5365
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    Redox competition mode of scanning electrochemical microscopy (RC-SECM) for visualisation of local catalytic activity

    K. Eckhard, X. Chen, F. Turcu and W. Schuhmann, Phys. Chem. Chem. Phys., 2006, 8, 5359
    DOI: 10.1039/B609511A

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