Strong Interaction between Platinum Nanoparticles and Tantalum-Doped Tin Oxide Nanofibers and Its Activation and Stabilization Effects for Oxygen Reduction Reaction

Abstract

Electrocatalyst supports stable to high potential are required for the proton exchange membrane fuel cell cathode. Electrocatalyst supports based on tantalum-doped tin oxide (Ta/SnO2) were prepared by electrospinning. The dopant amount was varied between 0 (undoped SnO2) and 7.5 at. %, and the resulting materials were characterized for their morphology, composition, structure, porosity, and electrical properties. Platinum nanoparticles prepared by a microwave-assisted polyol method were deposited with different loadings on 1 at. % Ta-doped SnO2 (1Ta/SnO2), selected for its highest electrical conductivity of 0.09 S cm-1. Their electrocatalytic properties toward the oxygen reduction reaction (ORR) were compared with those of the same particles deposited on carbon black and those of a commercial carbon-supported Pt catalyst. Pt/1Ta/SnO2 showed higher ORR activity and stability at high potential than Pt/C. In particular, the electrocatalyst with the lowest Pt loading (7 wt %) presented high mass activity and stability which, from XPS analysis, is suggested to result from very strong metal-support interaction. These results indicate that amongst tin oxides doped with pentavalent metals such as niobium (Nb/SnO2), antimony (Sb/SnO2), and tantalum, Ta/SnO2 has the advantage of both higher conductivity than Nb/SnO2 and greater stability in the fuel cell voltage range than Sb/SnO2.