Pt Nanoparticles Supported on Niobium-Doped Tin Dioxide: Impact of the Support Morphology on Pt Utilization and Electrocatalytic Activity

Two synthesis routes were used to design high surface area niobium-doped tin dioxide (Nb-doped SnO2, NTO) nanostructures with either loose-tube (fibre-in-tube) morphology using electrospinning or aerogel morphology using a sol-gel process. A higher specific surface area but a lower apparent electrical conductivity was obtained on the NTO aerogel compared to the loose tubes. The NTO aerogels and loose tubes and two reference materials (undoped SnO2 aerogel and Vulcan XC72) were platinized with a single colloidal suspension and tested as oxygen reduction reaction (ORR) electrocatalysts for proton-exchange membrane fuel cell (PEMFC) applications. The specific surface area of the supports strongly influenced the mass fraction of deposited Pt nanoparticles (NPs) and their degree of agglomeration. The apparent electrical conductivity of the supports determined the electrochemically active surface area (ECSA) and the catalytic activity of the Pt NPs for the ORR. Based on these findings, electrospinning appears to be the preferred route to synthesize NTO supports for PEMFC cathode application.