Structural Evolution of a PtRh Nanodendrite Electrocatalyst and Its Ultrahigh Durability toward Oxygen Reduction Reaction

Abstract

Durable Pt-based electrocatalysts toward oxygen reduction reaction (ORR) are essential preconditions for the commercialization of proton-exchange membrane fuel cells. However, dissolution of metal components as one major cause of the degradation of the Pt-based electrocatalysts has not yet been fully ameliorated in engineering aspects until now. Here, we report an ultradurable PtRh nanodendrite (PtRh ND) electrocatalyst, with remarkable 88% of mass activity retained after an accelerated durability test for 90,000 cycles. Experimental results demonstrate an intense structural evolution of the PtRh NDs and consequently the formation of a Pt-rich surface during the initial potential cycling, and this newly formed structure has strong resistance to dissolution. Density functional theory calculations reveal a “self-healing” effect that the difference in the dissolution energy of Pt and Rh atoms leads to this structural evolution. Besides, the synergy effect of the Pt-rich surface and the inner PtRh alloy suppresses the further dissolution of metal components and thus endow the catalyst with ultrahigh durability. The findings in this work provide inspirations for better designs of highly stable Pt-based ORR electrocatalysts.