An electrochemical, ellipsometric, and surface science investigation of the PtRu bulk alloy surface

We describe results of in situ and ex situ characterizations of the surface of a bulk PtRu alloy in sulfuric acid solutions at room temperature. Ellipsometric measurements taken during potential cycling show that a chemisorbed oxygen species forms on the PtRu alloy at potentials as low as +0.25 V vs. RHE. This is found also for Ru electrodes in the same solution. However, the surface oxygen species seems to form more reversibly on the alloy surface. The surface composition of the PtRu alloy appears to be stable up to +1.0 V vs. RHE. Both the in situ and ex situ techniques employed showed partial Ru loss from the surface of the alloy for potential excursions above +1.0 V. Implications of these results for the use of such PtRu alloys as carbon monoxide tolerant anode electrocatalysts in acid fuel cells are discussed.