Catalytic CO Oxidation on Single Pt-Atom Doped Aluminum Oxide Clusters: Electronegativity-Ladder Effect

• Published in: Journal of physical chemistry. C Vol. 119; no. 27; pp. 15414 - 15420
• Main Authors: Li, Xiao-Na, Yuan, Zhen, Meng, Jing-Heng, Li, Zi-Yu, He, Sheng-Gui
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.07.2015
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.5b04218

Single platinum-atom catalysts exhibit extraordinary activity in a large number of reactions. However, a consensus regarding the molecular origin of Pt catalysis is far from being reached. Here, benefiting from the study of atomic clusters, we propose the Electronegativity-Ladder (E-Ladder) effect to account for the origin of Pt catalysis. The concept was obtained from the study of single Pt-atom doped aluminum oxide clusters PtAl3O5–7 –, which are catalytically active in CO oxidation by molecular O2. The undoped aluminum oxide clusters, however, cannot drive such a catalytic cycle. The reactions have been identified by mass spectrometry and density functional theory calculations. The key to drive the cycle lies in the unique structure of PtAl3O6 –, in which the Pt atom that is not fully oxidized can coexist with the highly oxidative oxygen-centered radical (O–•). After the oxidation of one CO by PtAl3O7 –, the resulting PtAl3O6 – can also oxidize a second CO. The E-Ladder effect originates from the well-fitting electronegativity of the Pt atom (2.28) in between that of the Al atom (1.61) and the O atom (3.44), and this effect promotes the generation of an unpaired electron localized O–• radical, which results in the oxidative nature of PtAl3O6 – toward CO. Thus, the large enthalpy in the catalytic reaction (2CO + O2 → 2CO2) can be distributed much more evenly into several elementary reactions in the Pt–Al–O system than in the pure Al–O system.