Enhancement of the Oxygen Reduction Reaction (ORR) on a PtPb Nanoparticle /TiO₂/Cup-Stacked Carbon Nanotube Composite in Acidic Aqueous Solutions based on the Electronic Interaction between PtPb and TiO₂

PtPb ordered intermetallic nanoparticles (NPs) deposited on titanium oxide (TiO₂)/cup-stacked carbon nanotubes (CSCNT), PtPb NPs/TiO₂/CSCNT, were prepared by synthesis of TiO₂ with Ti-alkoxide under Ar atmosphere, by photodeposition of Pt NPs on the TiO₂ surface of TiO₂/CSCNT and by selective deposition of Pb atoms to Pt NPs with polyol method. The PtPb NPs/TiO₂/CSCNT is, at the first potential cycle, inferior to bench-marked Pt NPs/carbon black (Pt/CB) in the oxygen reduction reaction (ORR) in acidic aqueous solution, whereas after 100 potential cycles between 0.3 and 1.1 V (vs. RHE), the ORR was accelerated largely when compared with the Pt/CB. The ORR activity of PtPb NPs/CB degraded with potential cycle due to the dissolution of Pb from the surface of PtPb NPs. On the other hand, the dissolution of Pb was suppressed to a lesser degree on the PtPb NPs deposited on TiO₂ by the interaction between PtPb and TiO₂. The dealloyed NP surface composed of the Pt atoms and the residual Pb atoms is considered to bring about the enhancement of ORR.