Evolution of the Atomic Structure of Ceria-Supported Platinum Nanocatalysts: Formation of Single Layer Platinum Oxide and Pt–O–Ce and Pt–Ce Linkages

Abstract

Depending on platinum loading and gas environment vastly different platinum structures in Pt/ceria were observed by Pt L3-edge extended X-ray absorption (EXAFS) and X-ray absorption near-edge (XANES) spectroscopies. Calcination of highly loaded platinum (4 wt %) yielded stacked layers of α-PtO2. The low platinum-loaded sample (2 wt %), obtained by leaching, consisted of a single layer of α-PtO2 bonded to the support by Pt–O–Ce linkages. Reduction of the platinum oxide by exposure to a carbon monoxide and hydrogen (PROX) gas mixture led to complete metal reduction at temperatures above 540 K. Under these conditions platinum–cerium bonds with a distance of 2.4 Å were detected and particles of 0.8 and 0.6 nm for the high-loaded and low-loaded Pt/ceria samples, respectively.

Surface Engineering Protocol To Obtain an Atomically Dispersed Pt/CeO2 Catalyst with High Activity and Stability for CO Oxidation

“…It is clear that both CeO 2 -AA-Pt-cal and CeO 2 -IMP-Pt have a larger white line intensity than Pt foil, which suggests that the Pt species in these two catalysts carry a positive charge. 1,29 To assess the catalytic performance of the CeO 2 -AA-Pt-cal and CeO 2 -IMP-Pt samples, CO oxidation as a model oxidation reaction was performed at a gas hourly space velocity (GHSV) of 30,000 h −1 , using CeO 2 -IMP-Pt-cal (Figure S12) and blank CeO 2 as references (Figure 4a). The CeO 2 nanorods alone exhibited poor catalytic activity for CO oxidation, while CO oxidation over both CeO 2 -AA-Pt-cal and CeO 2 -IMP-Pt commenced at near room temperature (30 °C).…”

“…Herein, we propose a new strategy based on a facile surface engineering protocol using a molecule–surface charge transfer adduct to fabricate atomically dispersed noble metal catalysts, using the Pt/CeO 2 catalyst as a proof of concept. Pt is highly active for many oxidation reactions, including CO oxidation, , CO preferential oxidation reaction in H 2 -rich gases, ,− and three-way catalysis. ,− These reactions usually proceed at an elevated temperature (typically ∼80 °C for preferential oxidation reaction and ∼350 °C or higher for three-way catalysis), and thus it is crucial for Pt-based catalysts to avoid deactivation due to agglomeration of Pt atoms on the support during catalysis observed at these temperatures . Because of its excellent oxygen capacities, abundant surface oxygen vacancies, and easy shuttle between the 3+ and 4+ oxidation states, ceria (CeO 2 ) is considered a promising support for atomically dispersed metal catalysts for oxidation reactions. ,,,, In our proposed synthetic route, a large number of Ce 3+ sites are pre-reduced on the surface of a porous CeO 2 support through the adsorption of the reducing reagent l -ascorbic acid (AA), which enables the trapping of Pt atoms, preventing their migration and aggregation.…”

First-principles study of a new structure and oxidation mechanism of Pt3Zr

“…[15][16][17][18] In particular, Pt is a fascinating catalyst because it effectively promotes the process of ORR. [19][20][21] Recently, the oxidation behavior of Pt 3 Zr (0001) surface was studied by the experiment and rst-principles calculations.…”

Cerium(III) Nitrate Derived CeO2 Support Stabilising PtOx Active Species for Room Temperature CO Oxidation

“…It also should be noted that, the closely related polyatomic Pt−O−Pt bridged Pt 8 O 14 ensemble was identified as a representative base unit in the high‐performance CO oxidation that the Pt/CeO 2 catalysts generated via the restructuring of the single‐atom catalysts . Pt n O m clusters were also proposed as the best model to describe Pt L 3 ‐edge EXAFS spectra of the Pt/CeO 2 catalysts operating in the PROX process …”

“…[14] Pt n O m clusters were also proposed as the best model to describe Pt L 3edge EXAFS spectra of the Pt/CeO 2 catalysts operating in the PROX process. [71] Nevertheless, the main question arising is what factor is responsible for the difference in the CO oxidation light-off curves ( Figure 7A) for the PtO x /CeO 2 catalysts. A notable difference between the local atomic structure of Pt in the catalysts is the enlarged CN of the second coordination sphere (PtÀ Ce/Pt shell) for the "PtO x /CeO 2 -350" (CN = 3.0-4.0) catalyst in comparison with the "PtO x /CeO 2 -220" catalyst (CN = 2.0-3.0).…”