Acid Stability and Oxygen Reduction Activity of Magnetron-Sputtered Pt[sub 1−x]Ta[sub x] (0≤x≤1) Films

Abstract

Pt1−xTax(0≤x≤1)Pt1−xTax(0≤x≤1) thin-film libraries were prepared using combinatorial dc magnetron sputtering on a variety of substrates. For x<0.5xx0.5x0.5 a nanocrystalline phase of Pt1−xTaxPt1−xTax was observed. The bulk composition of the films obtained by electron microprobe before and after treatment in 0.5M0.5M H2SO4H2SO4 at 80°C showed no detectable dissolution of Ta at any xx in Pt1−xTaxPt1−xTax . X-ray photoelectron spectroscopy of acid-treated samples revealed that for regions with high Ta content (x0.5)(x0.5) , full oxidation of surface Ta had occurred. The samples, when used as oxygen-reduction electrocatalysts, also showed corrosion stability; however, the addition of Ta significantly lowered the activity towards oxygen reduction reaction for x0.1x0.1 in Pt1−xTaxPt1−xTax .