Oxygen reduction reaction on electrodeposited Pt100−x−yNixPdy thin films

The kinetics of the oxygen reduction reaction (ORR) were examined on a series of Pt100−x−yNixPdy ternary alloys. Films were produced by electrodeposition that involved a combination of underpotential and overpotential reactions. For Pt-rich Pt100−x−yNixPdy 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 Pt100−x−yNixPdy thin films revealed up to ∼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 Hupd charge reduced the enhancement factor to a value less than 2. The most active ternary alloy film for ORR was Pt25Ni73Pd2. Comparison of the ORR on Pt, Pt20Ni80, Pt25Ni73Pd2 thin films indicate that the binary alloy is the most active with a Hupd normalized ORR enhancement factor of up to 3.0 compared to 1.6 for the ternary alloy.