Effect of the d‑Band Center on the Oxygen Reduction Reaction Activity of Electrochemically Dealloyed Ordered Intermetallic Platinum–Lead (PtPb) Nanoparticles Supported on TiO₂‑Deposited Cup-Stacked Carbon Nanotubes

The electrocatalysis of PtPb ordered intermetallic nanoparticles (NPs)-deposited TiO₂/cup-stacked carbon nanotube (PtPb NPs/TiO₂/CS) catalysts for oxygen reduction reaction (ORR) was examined in 0.1 M HClO₄ aqueous solution. The as-prepared catalyst exhibited only a low activity for the ORR, but its ORR activity was found to be largely enhanced by the electrochemical dealloying, i.e., by the dissolution of Pb via a repeating potential scan cycling between 0.05 and 1.1 V vs RHE at 100 mVs^–1 in N₂-saturated 0.1 M HClO₄ aqueous solution, and to change drastically via a surface structural change of the PtPb NPs from the PtPb ordered intermetallic structure to the Pt₃Pb ordered intermetallic structure and further to the Pt₃Pb­(core)–Pt­(shell) structure with an increase in the potential scan cycling. We also found that changing the number of the potential scan cycling leads to a change in the d-band center of the resulting catalyst, and consequently, a so-called volcano-type corelationship between ORR activity and the d-band center was found to hold for a series of the electrochemically dealloyed PtPb NPs/TiO₂/CS catalysts. The maximum ORR activity was obtained for the Pt₃Pb catalyst prepared by the 200 cycles of potential scan cycling, the d-band center value of which is ca. 0.2 and 0.3 eV lower than those of the Pt NPs deposited on TiO₂/CS (Pt NPs/TiO₂/CS) and the Pt NPs deposited on carbon black (Pt NPs/CB), respectively, being in agreement with the expectation for the ORR electrocatalysis of Pt-based catalysts (Angew. Chem., Int. Ed. 2006, 45, 2897−2901).