Flame Spray Pyrolysis Achieves Size-Tunable Niobium-doped Tin Oxide Nanoparticles for Improved Catalyst Performance in PEFCs

Niobium-doped tin oxide (NTO) nanoparticles with a network structure, synthesized via flame aerosol technology, have attracted significant attention as catalyst supports in polymer electrolyte fuel cells due to their high durability and excellent cell performance. Here, we successfully synthesized NTO nanoparticles of varying sizes using spray flame techniques and systematically investigated the effects of solvent type, precursor concentration, feed rate, and oxygen dispersion gas flow rate on the crystallite size and particle size distribution of NTO nanoparticles. Increasing the mass input into the flame, through either higher precursor concentrations or higher feed rates, led to the formation of larger nanoparticles. We achieved the successful synthesis of NTO nanoparticles with controllable sizes in the range of 5 to 33 nm. The electrochemical surface area (ECSA) of Pt-loaded NTO particles with a 5 nm NTO size was 34.4 m²/g_–Pt, with Pt nanoparticles uniformly distributed across the NTO surface. The Pt/NTO sample with NTO nanoparticles of 17 nm exhibited high specific activity (j^spec_0.9 V) and mass activity (j^mass_0.9 V) at a potential of 0.9 V, with j^spec_0.9 V and j^mass_0.9 V values of 633 μA/cm² and 159 A/g, respectively.