Construction and Reactivity Screening of a Surface Composition Gradient for Combinatorial Discovery of Electro-Oxidation Catalysts

Materials possessing gradients in composition or structure are of interest for a range of applications, including the construction of functionally graded structural materials, as novel sensor and actuator platforms, and to control the site-specific binding of proteins and cells on surfaces. Gradients can also be used as sample libraries for combinatorial materials discovery that present an extremely dense sample set

Construction and Reactivity Screening of a Surface Composition Gradient for Combinatorial Discovery of Electro-Oxidation Catalysts

Materials possessing gradients in composition or structure are of interest for a range of applications, including the construction of functionally graded structural materials, as novel sensor and actuator platforms, and to control the site-specific binding of proteins and cells on surfaces. Gradients can also be used as sample libraries for combinatorial materials discovery that present an extremely dense sample set.This article is from Journal of Combinatorial Chemistry 6 (2004): 27-31, doi: 10.1021/cc034030k. Posted with permission.</p

Scanning Electrochemical Mapping of Spatially Localized Electrochemical Reactions Induced by Surface Potential Gradients

The influence of a surface potential gradient on the location and extent of electrochemical reactions was examined using a scanning electrochemical microscope. A linear potential gradient was imposed on the surface of a platinum-coated indium tin oxide electrode by applying two different potential values at the edges of the electrode. The applied potentials were used to control the location and extent of several electrochemical reactions, including the oxidation of Ru(NH3)62+, the oxidation of H2, and the oxidation of H2 in the presence of adsorbed CO. Scanning electrochemical mapping of these reactions was achieved by probing the feedback current associated with the oxidation products. The oxidation of Ru(NH3)62+ occurred at locations where the applied potential was positive of the formal potential of the Ru(NH3)62+/3+ redox couple. The position of this reaction on the surface could be spatially translated by manipulating the terminal potentials. The rate of hydrogen oxidation on the platinum-coated electrode varied spatially in the presence of a potential gradient and correlated with the nature of the electrode surface. High oxidation rates occurred at low potentials, with decreasing rates observed as the potential increased to values where platinum oxides formed. The extent of oxide formation versus position was confirmed with in-situ ellipsometry mapping. In the presence of adsorbed carbon monoxide, a potential gradient created a localized region of high activity for hydrogen oxidation at potentials between where carbon monoxide was adsorbed and platinum oxides formed. The position of this localized region of activity could be readily translated along the surface by changing the terminal potential values. The ability to manipulate electrochemical reactions spatially on a surface has potential application in microscale analytical devices as well as in the discovery and analysis of electrocatalytic systems.This article is from Langmuir22 (2006): 10322-10328, doi:10.1021/la0607048Posted with permission.</p