Bifunctional versus Defect-Mediated Effects in Electrocatalytic Methanol Oxidation.

The most prominent and intensively studied anode catalyst material for direct methanol oxidation fuel cells consists of a combination of platinum (Pt) and ruthenium (Ru). Classically, their high performance is attributed to a bifunctional reaction mechanism where Ru sites provide oxygen species at lower overpotential than Pt. In turn, they oxidize the adsorbed carbonaceous reaction intermediates at lower overpotential; among these, the Pt site-blocking carbon monoxide.

Pt nanocluster size effects in the hydrogen evolution reaction: approaching the theoretical maximum activity.

Hydrogen production from electrocatalytic water splitting in electrolyzers is a key process to store excess electric energy produced from intermittent renewable energy sources. For proton exchange membrane (PEM) electrolyzers, carbon supported platinum particles exhibit the highest rates for the hydrogen evolution reaction (HER); however, high Pt costs limit the wide spread use of this technology. By employing a graphene layer grown on a Ru(0001) single crystal as a template for Pt nanocluster (NC) growth, we studied the dependence of the HER activity on the NC size using NCs of different sizes.

Water and CO (co-)adsorption on pseudomorphic Pt films on Ru(0001) - a low-temperature scanning tunneling microscopy study.

Coadsorption of CO and water under ultrahigh vacuum (UHV) conditions can be considered as a model system for the interaction of metal surfaces with CO in an aqueous electrochemical environment. Nevertheless, this has rarely been investigated, and in particular for catalytically relevant bimetallic systems, there is hardly any information available. Here we report results of a low-temperature scanning tunneling microscopy (STM) study on the adsorption and coadsorption of CO and water on a Ru(0001) surface covered with a pseudomorphic Pt film of 2 or 3 monolayers thickness.

A combined UHV-STM-flow cell set-up for electrochemical/electrocatalytic studies of structurally well-defined UHV prepared model electrodes.

We describe the construction and discuss the performance of a novel combined ultrahigh vacuum (UHV)-electrochemistry set-up, allowing the controlled preparation and structural characterization of complex nanostructured electrode surfaces by high resolution scanning tunnelling microscopy (STM) under UHV conditions on the one hand and, after electrode transfer under clean conditions, electrochemical measurements under continuous, controlled electrolyte mass transport conditions on the other. Electrochemical measurements can be coupled with online product detection, either using an additional collector electrode or by differential electrochemical mass spectrometry (DEMS). The potential of the set-up will be illustrated in two electrocatalytic reactions on complex, but structurally well-defined bimetallic electrode surfaces, O reduction on PtAg/Pt(111) monolayer surface alloys and bulk CO oxidation on Pt monolayer island modified Ru(0001) electrodes.