Some Recent Studies in Ruthenium Electrochemistry and Electrocatalysis.

Ruthenium is a metal of a considerable importance in electrochemical science and technology. It is a catalyst or co-catalyst material in Pt-Ru alloys for methanol- and reformate hydrogenoxidation in fuel cells, while ruthenium oxide, a component in chlorine-evolution catalysts, represents an attractive material for electrochemical supercapacitors. Its facile surface oxidation generates an oxygen-containing species that provides active oxygen in some reactions. Ru sites in Pt-Ru catalysts increase the "CO tolerance" of Pt in the catalytic oxidation-reaction in direct methanol fuel cells (DMFC) and in reformate hydrogen-oxidation in proton exchange membrane fuel cells (PEMFC). The mechanism of Ru action is not completely understood, although the current consensus revolves around the so-called "bifunctional mechanism" wherein Ru provides oxygenated species to oxidize CO that blocks Pt sites, and has an electronic effect on Pt-CO interaction. While various studies of polycrystalline Ru go back several decades, those involving single crystal surfaces and the structural sensitivity of reactions on Ru surfaces emerged only recently. Using well-ordered single crystalline surfaces brings useful information as the processes on realistic catalysts are far too complex to allow identification of the microscopic reaction steps. In this article, we focus on progress in model systems and conditions, such as electrochemistry and electrocatalysis on bare and Pt-modified well-ordered Ru(0001) and Ru(10ī0) single-crystal surfaces. We also review the current understanding of the mechanistic principles of Pt-Ru systems and a new development of a Pt submonolayer on Ru support electrocatalyst. [ABSTRACT FROM AUTHOR]