Synthesis, Characterization of Nanostructured Rhodium Films and their Electrochemical Behavior towards Carbon Monoxide Oxidation

Abstract

Rhodium nanostructured thin film catalysts were prepared by pulsed laser deposition. The depositions were performed under vacuum and at different He background gas pressures ranging from 1 to 5 Torr. SEM, TEM, X-ray diffraction, and X-ray photoelectron spectroscopy were used to evaluate the morphology, the structure, the surface composition, and the electronic structure of the catalysts. Their electrochemical properties were studied towards CO stripping measurements in acidic solution; a reaction of critical issue to liquid fuel cells. It was discovered that rhodium (Rh) film deposited under 5 Torr of He background pressure showed the highest electroactive surface area, and the lowest onset potential of CO oxidation demonstrating an enhancement of the CO poisoning resistance. The reason for such enhanced electrocatalytic activity is ascribed to the high porosity and roughness of the Rh surface. Compared to Pt films made under similar processing conditions (5 Torr of He), Rh film displayed higher roughness factor of 58.5 (vs. 30 for Pt), a net charge due to oxidation and desorption of the CO adlayer of 385 μC cm−2 (vs. 350 μC cm−2 for Pt), and an onset potential for CO oxidation of 30 mV less anodic than that at Pt electrode.