Investigating Pt Atom Addition to Gas Phase Ce₂O_n Clusters Using Photoionization Efficiency Spectroscopy and Density Functional Theory

Abstract

Photoionization efficiency spectra for PtCe2O n (n = 0–1) clusters were recorded and compared with simulations based on density functional theory to determine adiabatic ionization energies (IE) and verify cluster structures. Calculated structures were also presented for PtCe2O2–5, though no comparison with experiment was made due to nondetection of these species in the mass spectrum. The IEs of PtCe2 and PtCe2O were determined to be 4.59 and 4.55 eV, respectively. The calculated IEs for PtCe2O2–5 sharply rise to >5.95 eV, coinciding with the HOMO of the clusters being lower energy Pt 6s-like, Ce 4f-like, and Pt 5d-like orbitals, from the higher energy Ce 6s-like HOMOs of PtCe2O0,1. The sharp increase in IE also explains the lack of PtCe2O2–5 ionization products observed in the experiment, though photodissociation is found to be a less likely possibility. As the level of oxidation in the clusters increased the charge on the Pt atom in the cluster became more positive, representing a transition from Ce → Pt to Pt → Ce charge transfer. This transition coincided with the formation of the first Pt–O–Ce structural motif and the sharp decrease in O bond dissociation energy in PtCe2O3. PtCe2O4 and PtCe2O5 each possess a second Pt–O–Ce site formed with the latter also having a sharp increase in calculated IE to 7.71 eV due to the low-energy Pt localized 5d-like HOMO.

Ionization Energies and Ground-State Structures of Neutral Lan (n = 2–14) Clusters: A Combined Experimental and Theoretical Investigation

“…The PIE spectra for La 9 and La 10 are wider in width and exhibit oscillatory behavior which could be due to the presence of multiple low-lying geometrical isomers in the thermally excited molecular beam, each having a different ionization threshold. A theoretical consideration of all potential PIE transitions, like it was done for small clusters of PtCe 2 and PtCe 2 O, 35 would help better understand these spectra. We have fitted the experimental data to a single curve, though to extract the VIE, ignoring the oscillatory part.…”

Electronic Structure of Heteronuclear Cerium-Platinum Clusters

“…Mixed cerium-platinum materials are found in an interesting array of applications ranging from catalysis to magnetic materials and heavy fermion conductors. The report from Bruix et al more than a decade ago, which detailed how strong interactions between Pt nanoparticle catalysts and CeO 2 support material resulted in enhanced activity toward the water-gas shift reaction, was followed by numerous studies geared toward characterizing the catalyst-support interactions. − In addition, Ce-doped Pt, Pt-doped ceria, − and CeO 2 nanostructure-supported single Pt atoms , have shown desirable properties as catalysts. In a closely related vein, research on Pt nanoparticles on defect-rich surfaces, , and the interactions of other metals, like Au, when supported on ceria, − has also been conducted.…”

Lanthanide Oxides: From Diatomics to High-Spin, Strongly Correlated Homo- and Heterometallic Clusters

“…Mixed Ce x V x′ O y + clusters have been studied by Asmis and co-workers using vibrational predissociation spectroscopy, which showed how the reducibility of Ce 4+ is an important factor governing the promoting role of ceria as a catalyst support material . Photoionization efficiency studies on transition metal-doped cerium oxide clusters, MCe x O y have shown how charge accumulation by the M centers evolves with cerium cluster oxidation ( y ). − Mixed Ce–Pt oxide clusters were also probed by Ray et al using anion PE spectroscopy . Mafuné and co-workers’ reactivity studies on mixed Ce x V x′ O y + showed O 2 desorption and preferential oxidation states of +4 and +5 .…”