Oxygen reduction reaction on electrodeposited Pt sub(100-x-y)Ni sub(x)Pd sub(y) thin films

The kinetics of the oxygen reduction reaction (ORR) were examined on a series of Pt sub(100-x-y)Ni sub(x)Pd sub(y) ternary alloys. Films were produced by electrodeposition that involved a combination of underpotential and overpotential reactions. For Pt-rich Pt sub(100-x-y)Ni sub(x)Pd sub(y) alloy films (x < 0.65) Ni co-deposition occurred at underpotentials while for Ni-rich films (x > 0.65) deposition proceeded at overpotentials. Rotating disk electrode (RDE) measurements of the ORR kinetics on Ni-rich Pt sub(100-x-y)Ni sub(x)Pd sub(y) thin films revealed up to [inline image]6.5-fold enhancement of the catalytic activity relative to Pt films with the same Pt mass loading. More than half of the electrocatalytic gain may be attributed to surface area expansion due to Ni dealloying. Surface area normalization based on the H sub(upd) charge reduced the enhancement factor to a value less than 2. The most active ternary alloy film for ORR was Pt sub(25)Ni sub(73)Pd sub(2). Comparison of the ORR on Pt, Pt sub(20)Ni sub(80), Pt sub(25)Ni sub(73)Pd sub(2) thin films indicate that the binary alloy is the most active with a H sub(upd) normalized ORR enhancement factor of up to 3.0 compared to 1.6 for the ternary alloy.