Long-term, stable, and improved oxygen-reduction performance of titania-supported PtPb nanoparticles

Abstract

The long-term, stable, and improved electrocatalytic performance towards the oxygen reduction reaction (ORR) has been achieved by anatase-type titania (TiO₂)-supported PtPb nanoparticles (NPs). Organometallic precursors, H₂PtCl₆·6H₂O and Pb(CH₃COO)₂ were co-reduced using sodium borohydride at ambient temperature to precipitate the PtPb NPs (NiAs-type structure, P6₃/mmc, a = 0.4259 nm; c = 0.5267 nm, average particle size: 3 nm) over the TiO₂ support (PtPb/TiO₂). PtPb/TiO₂ showed substantial electrocatalytic activity towards ORR both in terms of the onset potential and the mass activity compared to TiO₂-supported Pt NPs (Pt/TiO₂). The onset potential of PtPb/TiO₂ was shifted to a higher electric potential by 180 mV compared to Pt/TiO₂. Also, PtPb/TiO₂ showed a seven-times higher ORR mass activity than Pt/TiO₂. Neither the onset potential nor the mass activity of PtPb/TiO₂ was altered after ORR cycles, whereas those of commercially available Vulcan carbon-supported Pt NPs (Pt/VC; Pt loading: 20 wt%) were largely altered. The PtPb NPs were not agglomerated over the TiO₂ support even after repeated cycles under the electric potential condition, as the result of the strong interactions between the PtPb NPs and the TiO₂ support, but the Pt NPs were significantly agglomerated over the TiO₂- and the Vulcan carbon-supports due to the weak interactions between the Pt NPs and the supports. PtPb/TiO₂ can be a practical cathode material for direct fuel cells in terms of its long-term stability and enhanced catalytic performance.