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

Abstract

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 PtAl 3 O 5−7 − , which are catalytically active in CO oxidation by molecular O 2 . 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 PtAl 3 O 6 − , 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 PtAl 3 O 7 − , the resulting PtAl 3 O 6 − 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 PtAl 3 O 6 − toward CO. Thus, the large enthalpy in the catalytic reaction (2CO + O 2 → 2CO 2 ) can be distributed much more evenly into several elementary reactions in the Pt−Al−O system than in the pure Al−O system.

Noble‐Metal‐Free Single‐Atom Catalysts CuAl4O7–9− for CO Oxidation by O2

“…This step is the bottleneck of the whole reaction, indicating that Cu + is reluctant to be oxidized to Cu 2+ during O−O dissociation. The behavior of Cu is significantly different from that of NM, which can be oxidized during O−O bond dissociation . Upon the adsorption of a second CO, Cu + is maintained in I6 and then the barrier of O−O bond dissociation decreases to 0.93 eV (I7→TS7→I8→TS8).…”

“…CO oxidation is a type of the best studied reaction and heteronuclear metal oxide clusters are ideal models to reveal the nature of active sites of supported catalysts. Available examples with single NM atoms are AuAl 3 O 3–5 +[12] and PtAl 3 O 5–7 − . Both the single NM atoms and the O .− radical are crucial to drive the catalysis.…”

Reactions of metal cluster anions with inorganic and organic molecules in the gas phase

“…75,86,[89][90][91]93,104,105,116, The importance of spin in determining the reactivity of metal clusters toward molecular oxygen has been emphasized. The ground state of molecular oxygen is spin triplet ( 3 O 2 ), where the majority spin states have a pair of unpaired electrons while the minority states are unfilled.…”

Mechanisms investigation of the WGSR catalyzed by single noble metal atoms supported on vanadium oxide clusters

“…Single‐atom catalysis (SAC), which consists of isolated metal single atoms (SAs) dispersed on support and possess unique chemical and physical properties, has attracted increasing interest in maximizing the use of noble metal atoms and showed high activity and selectivity as a new frontier in heterogeneous catalysis . In many instances, SAC provides not only the highest activities but also remains extremely stable in the course of catalytic reactions, primarily attributed to the strong bonding between the metal single atoms and the corresponding active sites on the support surface.…”