Sensitivity of CO oxidation toward metal oxidation state in ceria-supported catalysts: an operando DRIFTS-MS study

Abstract

The oxidation of carbon monoxide has been studied on pristine CeO 2 , Rh-CeO 2 , and Pt-CeO 2 powders prepared in one step by solution combustion synthesis (SCS). The reaction was cycled between an oxygenrich and a CO-rich feed with regard to the stoichiometric conditions. CO 2 production was monitored by mass spectrometry, while the surface species were probed by operando DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy). Whereas the reaction starts above 150°C on CeO 2 and Rh-CeO 2 and does not depend on the state of the surface (oxidized or reduced), the reaction on Pt-CeO 2 shows strong dependency on the initial state and substantial activity is achieved at much lower temperatures with the CO-rich feed. We relate this result to the change in the oxidation state of Pt via strong interaction with ceria.

Exploiting Synergies in Catalysis and Gas Sensing using Noble Metal‐Loaded Oxide Composites

“…Vibrational spectroscopies, like DRIFTS and Raman spectroscopy, are commonly used to gain insights into the surface chemistry of active materials. In catalysis DRIFTS is applied to investigate the adsorption of reactants on or the poisoning of the active sites at the catalyst surface and the restructuring of catalyst materials . Demoulin et al .…”

“…By studying the CO oxidation over Pt/Al 2 O 3 catalysts with in situ / operando DRIFTS it was possible to directly correlate the catalytic activity to the adsorption characteristics of CO, the structure of the Pt particles, the surface species and the evolving reaction products (cf. Figure ) . In a very recent in situ and operando study we employed complementary microscopic and spectroscopic techniques (in situ environmental transmission electron microscopy (ETEM) & operando XAS) and encountered a highly dynamic structural behavior of Pt nanoparticles on ceria, with dramatic consequences for the CO light‐off.…”

Transformation of a Pt–CeO2 Mechanical Mixture of Pulsed‐Laser‐Ablated Nanoparticles to a Highly Active Catalyst for Carbon Monoxide Oxidation

“…There, the oxidation state of platinum, its dispersion, and microstructure substantially depend on the reaction medium used for the catalyst treatment . A variety of platinum states is formed through a strong chemical interaction with the support (SMSI effect), so that platinum can be in cationic states and in different metallic cluster species . The interaction of metallic platinum particles with ceria, studied in many publications, was shown to increase the catalytic activity per platinum atom in comparison, for example, with the Pt/Al 2 O 3 catalyst .…”

Uncovering the 3 D Structure of Combustion‐Synthesized Noble Metal‐Ceria Nanocatalysts

“…According to the powder XRD analysis previously reported, the freshly prepared Pt‐CeO 2 sample exhibited the expected fluorite structure of standard CeO 2 (space group F m m , #225) with a lattice parameter of 5.4123 Å and an average crystallite size of 27 nm (both determined from Rietvield refinement); no Pt phase was discernable on the diffractograms recorded in ambient conditions. Other analyses of this sample using HRTEM, Raman spectroscopy, IR spectroscopy of adsorbed CO and X‐ray photoelectron spectroscopy, have been reported elsewhere …”

“…Other analyses of this sample using HRTEM, Raman spectroscopy,I Rs pectroscopy of adsorbed CO and X-ray photoelectron spectroscopy,have been reported elsewhere. [3,41,42] Using the BET method, as pecific surface area of 25 m 2 g À1 was derived from the N 2 physisorption isotherm shown in Figure 1. The isotherm is of II/IV composite type with aH 3h ysteresis loop and quasi vertical parallel branches at high pressure.…”