Z. Liu, D. Huang, S. Koh, C. Yu, K.L. More, L.F. Allard Jr., P. Strasser
We reported here that the enhanced electrocatalytic oxygen reduction activity of PtCu3/C catalysts was stabilized using Au galvanic displacement of Cu in PtCu3/C. The results showed that mass activities decreased by 24 and 29%, and specific activities decreased by 6 and 26% for Pt/C and PtCu3/C catalysts, respectively, while PtCu3/C modified by Au can retain both mass and specific activities after 1000 potential cycles between 0.6 and 1.0V vs RHE. XRD patterns showed that additional peaks related to Au-riched phase appeared, while the peaks related to PtCu alloy phase didn’t change much. In combination with XPS analysis, Cu in PtCu3/C catalysts was displaced spontaneously by Au3+. EDS analysis combined with HRTEM showed big particles were enriched with Au, while small particles were enriched with Pt. STEM showed Pt-Au shell Pt-Cu core structures. Au atoms in PtCu3/C catalysts affected electronic structure of Pt-enriched shell, and therefore improved the ORR activity compared to the dealloyed PtCu3/C catalysts. On the other hand, Au atoms inhibited Pt oxidation and helped to keep favorable Pt-Pt distances created by dealloying, thus improving the stability of ORR activity on PtCu3/C catalysts.