Highly Dispersed and Crystalline Ta₂O₅ Anchored Pt Electrocatalyst with Improved Activity and Durability Toward Oxygen Reduction: Promotion by Atomic-Scale Pt–Ta₂O₅ Interactions

Abstract

Developing highly active and durable Pt-based electrocatalysts for the oxygen reduction reaction (ORR) is a crucial target if actual commercial application of proton exchange membrane fuel cells (PEMFCs) is to be realized. Herein we show that utilizing highly dispersed and crystalline Ta2O5-modified carbon nanotubes (CNTs) as a support can stabilize Pt nanoparticles (NPs) by strengthening the metal–support interactions at the atomic scale, and furthermore, we show that this offers an efficient strategy to improve the ORR catalytic activity and durability of the Pt NPs. These were found to be selectively anchored on the interface of well-dispersed Ta2O5 NPs and CNTs, showing an atomic-coupled interfacial structure between Pt and Ta2O5 with lattice overlap of Pt (200) and Ta2O5 (001). X-ray absorption near edge structure (XANES) analysis shows that the electronic structure of Pt is perturbed by Ta2O5 by virtue of the formation of strong Pt–O–Ta bonds. The presence of highly crystalline Ta2O5 also induces the growth of polyhedral-structured Pt NPs with the exposure of abundant (111) and (100) facets, leading to an improved ORR activity for Pt–Ta2O5/CNT. As a result, our Pt–Ta2O5/CNT electrocatalyst exhibits high ORR activity with a large electrochemical surface area of 78.4 m2 g–1 and a mass activity of 0.23 A mg–1Pt at 0.9 V (this represents a 3.4- and 2.2-fold improvement over the corresponding activities of commercial Pt/C and Pt/CNT catalysts, respectively). Most importantly, Pt–Ta2O5/CNT possesses superior long-term durability without any obvious degradation after 10 000 cycles and thus outperforms both of the commercial Pt/C and Pt/CNT catalysts. Our strategy of using highly dispersed and crystalline Ta2O5 to stabilize Pt NPs, resulting in strengthened metal–support interactions, should facilitate the development of high-performance Pt-based ORR electrocatalysts for use in fuel cells.