Relevance of IR Spectroscopy of Adsorbed CO for the Characterization of Heterogeneous Catalysts Containing Isolated Atoms

Meunier, Frédéric

doi:10.1021/acs.jpcc.1c06784

Cited by 71 publications

(60 citation statements)

References 64 publications

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“…As shown in Figure , all samples only showed a peak located around 2090 cm –1 , which we assign to CO adsorbed on isolated Pt 2+ cations (i.e., Pt single atoms). ,, We recognize that other authors have reported CO-IR bands assigned to CO-Pt isolated species in Pt/ceria, ranging from 2088 to 2095 cm –1 . − It has also been suggested that definitive assignment of the adsorbed CO band can only be performed with samples that have very low Pt loading (0.05 wt %) since higher loadings can lead to the formation of sub-nanometer clusters . Meunier has described the challenges in unambiguously assigning IR bands. We note that our assignment of the band in Figure is based not just on the peak position but the physical characteristics of the CO band as well.…”

Section: Resultssupporting

confidence: 57%

“…20−23 It has also been suggested that definitive assignment of the adsorbed CO band can only be performed with samples that have very low Pt loading (0.05 wt %) since higher loadings can lead to the formation of sub-nanometer clusters. 24 Meunier 25 has described the challenges in unambiguously assigning IR bands. We note that our assignment of the band in Figure 8 is based not just on the peak position but the physical characteristics of the CO band as well.…”

Section: ■ Results and Discussionsupporting

confidence: 52%

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Designing Ceria/Alumina for Efficient Trapping of Platinum Single Atoms

Pham

DeLaRiva

Peterson

et al. 2022

ACS Sustainable Chem. Eng.

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Cerium oxide (ceria) has been shown to be very effective at trapping platinum atoms due to formation of stable surface complexes at step edges, where coordinatively unsaturated cerium cations are present. But ceria loses its effectiveness when heated to high temperatures due to loss of surface area and growth in particle size associated with sintering of the oxide. Being a rare earth, and with limited supplies worldwide, it is important to develop methods to improve the effectiveness of ceria as a catalyst support. Here, we explore the performance for trapping Pt atoms when the ceria is supported on a high surface area alumina carrier. This helps create a more sustainable catalyst formulation, especially if we can retain the high dispersion of Pt seen on ceria supports. For this work, we studied the atom trapping efficacy of ceria/alumina samples with increasing ceria content (8−50 wt %) and contrasted the behavior with pure ceria. Electron microscopy reveals that when dispersed on alumina, ceria is present in the form of crystalline nanoparticles and isolated cerium ions. These two forms of ceria differ markedly in their ability to trap Pt atoms. Atomically dispersed cerium is present in the form of Ce 3+ cations on alumina; however, this form of ceria is not effective for trapping Pt atoms. Our results show that the atom-trapped Pt resides primarily on crystalline ceria nanoparticles. CO oxidation was used as a probe reaction to evaluate the performance of these Pt AT / ceria-alumina catalysts. We conclude that over the range of ceria loadings we investigated, 50% ceria/alumina represents the optimal catalyst support for achieving high surface area and atom trapping efficiency while helping reduce the total ceria content in this catalyst system.

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Section: Resultssupporting

confidence: 57%

Section: ■ Results and Discussionsupporting

confidence: 52%

Designing Ceria/Alumina for Efficient Trapping of Platinum Single Atoms

Pham

DeLaRiva

Peterson

et al. 2022

ACS Sustainable Chem. Eng.

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“…This difference is significant, but not as large as in a previously reported study, where FWHM was ~10, 25, and 40 cm −1 for CO adsorbed on metallic Pt [41]. The broadening of CO adsorption peak is presumably attributable to inhomogeneity of adsorption sites and can be related to different sizes of metallic particles [42].…”

Section: Co-driftscontrasting

confidence: 49%

Local Structure of Pd1 Single Sites on the Surface of PdIn Intermetallic Nanoparticles: A Combined DFT and CO-DRIFTS Study

et al. 2021

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Local structure of Pd1 single sites on the surface of Pd1In1 intermetallic nanoparticles supported on α-Al2O3 was investigated by the combination of CO-DRIFTS spectroscopy and DFT. CO-DRIFTS spectra of PdIn/Al2O3 catalyst exhibit only one asymmetric absorption band of linearly adsorbed CO comprising two peaks at 2065 and 2055 cm−1 attributable to CO molecules coordinated to Pd1 sites located at (110) and (111) facets of PdIn nanoparticles. The absence of bridged or hollow-bonded CO bands indicates that multipoint adsorption on PdIn nanoparticles is significantly hindered or impossible. DFT results show that on (110) facet multipoint CO adsorption is hindered due to large distance between neighboring Pd atoms (3.35 Å). On (111) facet multipoint CO adsorption on surface palladium atoms is impossible, since adjacent Pd atoms are located below the surface plane.

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“…This band may be assigned to CO adsorbed on partially oxidized Pt. Several authors have proposed that CO could bound strongly to PtOx species and be unreactive [9,27,38], although the exact nature of the sites, e.g., single Pt cation or PtOx clusters, is still debated, as discussed in a recent review [31]. The main linear CO band on the Pt/alumina sample can thus be assigned to two different Pt species, one oxidized (2085 cm −1 ) and one reduced (ca.…”

Section: Resultsmentioning

confidence: 99%

“…The samples used here exhibits a more complex IR signal than those reported in previous studies [6,30], indicating the presence of various metallic and cationic Pt species. It must be stressed that the present study did not aim at determining the exact nature of the bands observed, particularly those located around 2090 cm −1 on Pt/CeO 2 , the assignment of which is still controversial [31]. The effect of the presence of molecular oxygen will also be assessed.…”

Section: Introductionmentioning

confidence: 94%

Stability of Pt-Adsorbed CO on Catalysts for Room Temperature-Oxidation of CO

et al. 2022

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A large signal of gas-phase CO overlapping with those of adsorbates is often present when investigating catalysts by operando diffuse reflectance FT-IR spectroscopy. Physically removing CO(g) from the IR cell may lead to a fast decay of adsorbate signals. Our work shows that carbonyls adsorbed on metallic Pt sites fully vanished in less than 10 min at 30 °C upon removing CO(g) when redox supports were used. In contrast, a broad band assigned to CO adsorbed on oxidized Pt sites was stable. It was concluded that physically removing CO(g) at room temperature during IR analyses will most likely lead to changes in the distribution of CO(ads) and a misrepresentation of the Pt site speciation, misguiding the development of efficient low-temperature CO oxidation catalysts. A tentative representation of the nature of the Pt phases present depending on the feed composition is also proposed.

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Relevance of IR Spectroscopy of Adsorbed CO for the Characterization of Heterogeneous Catalysts Containing Isolated Atoms

Cited by 71 publications

References 64 publications

Designing Ceria/Alumina for Efficient Trapping of Platinum Single Atoms

Designing Ceria/Alumina for Efficient Trapping of Platinum Single Atoms

Local Structure of Pd1 Single Sites on the Surface of PdIn Intermetallic Nanoparticles: A Combined DFT and CO-DRIFTS Study

Stability of Pt-Adsorbed CO on Catalysts for Room Temperature-Oxidation of CO

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