Electrodeposited Pt-Ir Thin Films as DMFC Anode Materials

Pt-Ir alloys have been reported previously to be very good catalysts towards the methanol oxidation reaction (MOR), although the composition of these films was not known with certainty. In the present work, thin Pt-Ir films of varying, but controlled, composition were fabricated using electrodeposition, with a charge efficiency of close to 100%. X-ray photoelectron spectroscopy (XPS) analysis showed that the film composition is fully homogeneous with depth into the film and that it matches very closely with the metal molar ratio in the deposition solution. The Pt-Ir film composition with the highest MOR activity was found to have a 2:1 Pt:Ir mass ratio and 1:1 surface composition ratio, based on measurements of the underpotentially deposited adsorbed hydrogen charge.