Details

Autor(en) / Beteiligte

• Gun Oh, Dong
• Aleksandrov, Hristiyan A.
• Kim, Haneul
• Koleva, Iskra Z.
• Khivantsev, Konstantin
• Vayssilov, Georgi N.
• Hun Kwak, Ja

Titel

Key Role of a‐Top CO on Terrace Sites of Metallic Pd Clusters for CO Oxidation

Ist Teil von

• Chemistry : a European journal, 2022-09, Vol.28 (49), p.e202200684-n/a

Ort / Verlag

Germany: Wiley Subscription Services, Inc

Erscheinungsjahr

2022

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• Pd‐based catalysts are the most widely used for CO oxidation because of their outstanding catalytic activity and thermal stability. However, fundamental understanding of the detailed catalytic processes occurring on Pd‐based catalysts under realistic conditions is still lacking. In this study, we investigated CO oxidation on metallic Pd clusters supported on Al2O3 and SiO2. High‐angle annular dark‐field scanning transmission electron microscopy revealed the formation of similar‐sized Pd clusters on Al2O3 and SiO2. In contrast, CO chemisorption analysis indicated a gradual change in the dispersion of Pd (from 0.79 to 0.2) on Pd/Al2O3 and a marginal change in the dispersion (from 0.4 to 0.24) on Pd/SiO2 as the Pd loading increased from 0.27 to 5.5 wt %; these changes were attributed to differences in the metal‐support interactions. Diffuse reflectance infrared Fourier‐transform spectroscopy revealed that fewer a‐top CO species were present in Pd supported on Al2O3 than those in Pd supported on SiO2, which is related to the morphological differences in the metallic Pd clusters on these two supports. Despite the different dispersion profiles and surface characteristics of Pd, O2 titration demonstrated that linearly bound CO (with an infrared signal at 2090 cm−1) reacted first with oxygen in the case of CO‐saturated Pd on Al2O3 and SiO2, which suggests that a‐top CO on the terrace site plays an important role in CO oxidation. The experimental observations were corroborated by periodic density functional calculations, which confirmed that CO oxidation on the (111) terrace sites is most plausible, both kinetically and thermodynamically, compared to that on the edge or corner sites. This study will deepen the fundamental understanding of the effect of Pd clusters on CO oxidation under reaction conditions. O2 titration using in situ DRIFTS was performed on metallic Pd cluster supported on Al2O3 saturated with CO. The most weakly adsorbed a‐top CO adsorbed on terrace site preferentially reacted with oxygen than other CO species. It clearly demonstrated that the CO oxidation is initiated with a‐top CO on terrace sites.