Hydrothermal Synthesis of ZnO–doped Ceria Nanorods: Effect of ZnO Content on the Redox Properties and the CO Oxidation Performance

Sofia Stefa,Michalis Konsolakis,Vasillios Binas,Vassilis N. Stathopoulos,Maria Lykaki,Pavlos K. Pandis

doi:10.3390/app10217605

Abstract

The rational design of highly efficient, noble metal-free metal oxides is one of the main research priorities in the area of catalysis. To this end, the fine tuning of ceria-based mixed oxides by means of aliovalent metal doping has currently received particular attention due to the peculiar metal-ceria synergistic interactions. Herein, we report on the synthesis, characterization and catalytic evaluation of ZnO–doped ceria nanorods (NR). In particular, a series of bare CeO2 and ZnO oxides along with CeO2/ZnO mixed oxides of different Zn/Ce atomic ratios (0.2, 0.4, 0.6) were prepared by the hydrothermal method. All prepared samples were characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction (TPR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). The CO oxidation reaction was employed as a probe reaction to gain insight into structure-property relationships. The results clearly showed the superiority of mixed oxides as compared to bare ones, which could be ascribed to a synergistic ZnO–CeO2 interaction towards an improved reducibility and oxygen mobility. A close correlation between the catalytic activity and oxygen storage capacity (OSC) was disclosed. Comparison with relevant literature studies verifies the role of OSC as a key activity descriptor for reactions following a redox-type mechanism.

Highlights

Cerium oxide or ceria (CeO2 ) is considered one of the most promising metal oxides for numerous catalytic applications, such as catalytic oxidation of CO [1,2,3], NO reduction [4,5,6], water–gas shift reaction [7,8,9,10], reforming reactions [11,12] and soot combustion [13,14,15]
Sci. 2020, 10, 7605 nanocomposites of different shape, ceria nanorods possess enhanced reducibility that is linked to their high population in intrinsic defects and oxygen vacancies
The latter is considered responsible for their superior CO oxidation performance [21]

Summary

Introduction

Cerium oxide or ceria (CeO2 ) is considered one of the most promising metal oxides for numerous catalytic applications, such as catalytic oxidation of CO [1,2,3], NO reduction [4,5,6], water–gas shift reaction [7,8,9,10], reforming reactions [11,12] and soot combustion [13,14,15]. During the past few decades, nanotechnology has made remarkable progress toward the development of ceria nanocomposites with distinct physical and chemical properties, greatly expanding their potential applications in energy and environmental catalysis [19,20]. In this perspective, we recently showed that among ceria. Sci. 2020, 10, 7605 nanocomposites of different shape, ceria nanorods possess enhanced reducibility that is linked to their high population in intrinsic defects and oxygen vacancies. The latter is considered responsible for their superior CO oxidation performance [21]

Methods

Results

Conclusion