Enhanced ORR Kinetics on Au-Doped Pt–Cu Porous Films in Alkaline Media
Yunxiang Xie, Yao Yang, David A. Muller, Héctor D. Abruña, Nikolay Dimitrov, Jiye Fang
Abstract
Fraction-controlled Pt–Cu-based porous films were prepared using an electrochemical deposition–stripping synthetic approach, and their structure, composition, and electronic structure were characterized using scanning/transmission electron microscopy-energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques. These materials exhibited superb electrocatalytic activity toward the oxygen reduction reaction (ORR) in alkaline media. For example, the mass activity of a Pt45Cu55 film, at 0.90 V (vs RHE), was 3.5× higher than that of commercial Pt/C (40 wt % Pt). This activity enhancement is attributed, in part, to the ligand effect of the Cu component. The introduction of Au, as a third metal constituent to the porous films, further improved the ORR performance significantly. The synergistic effect(s) of Au and Pt appear to have a critical impact on the enhancement of the ORR activity. Compositional optimization identified the dealloyed Pt37Cu56Au7 porous film as the best performing electrocatalyst. It also exhibited the highest mass and specific activities (0.871 A/mgPt, 1.85 mA/cm2) which were 7.20× and 8.15× higher than those of commercial Pt/C (40 wt % Pt), respectively. This ternary alloy thin-film catalyst also exhibited the longest durability, among all tested samples in this study.