Transformation of Highly Stable Pt Single Sites on Defect Engineered Ceria into Robust Pt Clusters for Vehicle Emission Control

Abstract

Engineering surface defects on metal oxide supports could help promote the dispersion of active sites and catalytic performance of supported catalysts. Herein, a strategy of ZrO 2 doping was proposed to create rich surface defects on CeO 2 (CZO) and, with these defects, to improve Pt dispersion and enhance its affinity as single sites to the CZO support (Pt/CZO). The strongly anchored Pt single sites on CZO support were initially not efficient for catalytic oxidation of CO/C 3 H 6 . However, after a simple activation by H 2 reduction, the catalytic oxidation performance over Pt/CZO catalyst was significantly boosted and better than Pt/CeO 2 . Pt/CZO catalyst also exhibited much higher thermal stability. The structural evolution of Pt active sites by H 2 treatment was systematically investigated on aged Pt/CZO and Pt/CeO 2 catalysts. With H 2 reduction, ionic Pt single sites were transformed into active Pt clusters. Much smaller Pt clusters were created on CZO (ca. 1.2 nm) than on CeO 2 (ca. 1.8 nm) due to stronger Pt-CeO 2 interaction on aged Pt/CZO. Consequently, more exposed active Pt sites were obtained on the smaller clusters surrounded by more oxygen defects and Ce 3+ species, which directly translated to the higher catalytic oxidation performance of activated Pt/CZO catalyst in vehicle emission control applications.

Fine-tuned local coordination environment of Pt single atoms on ceria controls catalytic reactivity

“…H 2 -TPR technique is a powerful tool to evaluate the dispersion of Pt species as well as the strength of Pt-O-Ce interaction on Pt/CeO 2 based catalysts 39 , 40 . Herein, the H 2 -TPR profiles of Pt/CeO 2 -550, Pt/CeO 2 -700, Pt/CeO 2 -800 were collected to investigate the interaction between Pt single atoms and CeO 2 support (Fig.…”

Oxygen vacancies in a catalyst for VOCs oxidation: synthesis, characterization, and catalytic effects

“…Recently, Liu et al prepared a zirconium-doped CeO 2 (CZO) catalyst rich in oxygen defects by doping zirconium into the lattice of CeO 2 and proved the existence of abundant oxygen vacancies on the surface of the CZO support using this characterization method. 100…”

“…9D, Liu et al used abundant surface defects in zirconium-doped CeO 2 (CZO) carriers to anchor Pt, which improved the dispersion of Pt and made it outstanding in propylene oxidation. 100 He et al found that the oxygen vacancies of CeO 2 could stabilize Pt atoms and proposed that the stabilization mechanism relied on the distortion of the Pt-O-Ce interface formed by the strong metal-carrier interaction to maintain thermodynamic stability. 37 In addition, many studies have accepted oxygen vacancies as Lewis acid sites to compensate for the acidity of catalysts.…”

Leveraging Pt/Ce1–xLaxO2−δ To Elucidate Interfacial Oxygen Vacancy Active Sites for Aerobic Oxidation of 5-Hydroxymethylfurfural

“…The generation of asymmetric oxygen vacancies and their boosted catalytic oxidation activity have been demonstrated on various redox reaction systems. 17−21 The oxygen vacancies on oxides can act as trapping and stabilizing centers for metal atoms and clusters, 22 generating asymmetric interfacial oxygen vacancy sites 23,24 and promoting charge transfer between metal and oxide substrates. 25 It was reported that Pt atoms could be stabilized on oxygen vacancies of CeO 2 through a spontaneous interfacial distortion to form Pt−O−Ce interfacial sites, which were advantageous to the adsorption and activation of O 2 and methanol.…”