Imaging the reactivity of electro-oxidation catalysts with the scanning electrochemical microscope

We describe an application of the scanning electrochemical microscope that utilizes tip-sample feedback to characterize the reactivity of electro-oxid ation catalysts. The kinetics of hydrogen oxidation are probed at a platinu m electrode as a function of applied potential in aqueous sulfuric acid sol ution. Tip-sample feedback generates a tip response that reflects the rate of hydrogen oxidation at the substrate. The ability to directly measure the rate constant for hydrogen oxidation is, subsequently, used to perform rea ctivity mapping of heterogeneous electrodes consisting of catalytic and non catalytic domains. Differences in reaction kinetics clearly distinguish sur face composition variations based upon their reactivity toward hydrogen oxi dation and illustrate the capability of this technique as a screening tool in the design of electrocatalysis. Further experiments investigating the ox idation of methanol illustrate the ability to characterize complex multiste p reactions. (C) 2000 The Electrochemical Society. All rights reserved.