Interface dynamics of Pd–CeO2 single-atom catalysts during CO oxidation

Abstract

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Controlling Multiple Active Sites on Pd−CeO2 for Sequential C−C Cross‐coupling and Alcohol Oxidation in One Reaction System

“…For Pd 1 À CeO 2 , the bands at 2,130 cm À 1 and 2,095 cm À 1 are observed from the linearly adsorbed CO on ionic Pd in different conditions of oxygen coordination. [36][37][38] The band from linearly adsorbed CO blue-shifted to 2,090 cm À 1 and 2,085 cm À 1 in Pd NC À CeO 2 and Pd NP À CeO 2 , which confirms the reduced character of their surface Pd. Moreover, the bands from bridged CO on Pd (1,959 cm À 1 and 1,966 cm À 1 ) and threefold CO on Pd (1,887 cm À 1 ) gradually evolved in the DRIFT spectra of Pd NC À CeO 2 to Pd NP À CeO 2 .…”

“…Interestingly, this shoulder peak decreased in the XPS spectra of Pd NP À CeO 2 . Since previous studies have underlined the formation of Ce 3 + species at PdÀ CeO 2 interface sites, [22,38] the difference in Ce 3d XPS spectra of PdÀ CeO 2 catalysts implies the change in the amount of PdÀ CeO 2 interface sites on Pd 1 À CeO 2 , Pd NC À CeO 2 , and Pd NP À CeO 2 . Therefore, the ratio of Ce 3 + to Ce 4 + was calculated by peak deconvolution of Ce 3d XPS spectra for quantitative comparison of Ce 3 + species.…”

A minireview on the synthesis of single atom catalysts

“…For instance, Muravev et al used two methods, the traditional impregnation and flame spray pyrolysis, to synthesize Pd 1 /CeO 2 catalysts. 169 For both of the two Pd 1 /CeO 2 catalysts, there were no Pd or PdO clusters on the surface of CeO 2 (as evidenced by HAADF-STEM, Fig. 15 ).…”

Synchrotron-radiation spectroscopic identification towards diverse local environments of single-atom catalysts

“…Muravev et al compared the interface dynamics of two singleatom Pd/CeO 2 catalysts fabricated by conventional impregnation marked as 1PdRods and one-step ame spray pyrolysis (FSP) as 1PdFSP respectively for low-temperature CO oxidation. 138 In situ NAP-XPS demonstrates the appearance of small PdO x clusters at 336.1 eV and even metallic Pd at 335.4 eV in 1PdRods while absence in 1PdFSP under 2 mbar pressure conditions including CO and O 2 , showing the structural stability owing to stronger metal-support interactions (MSIs) by FSP (Fig. 11a and b).…”