Catalytic Behaviour of Flame-Made CuO-CeO2 Nanocatalysts in Efficient CO Oxidation

Feng Zhao,Shuangde Li,Xicuo Zha,Yuzhou Deng,Xiaofeng Wu,Renliang Yue,Yunfa Chen,Weiman Li

doi:10.3390/catal9030256

Abstract

CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The inﬂuences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diﬀraction (XRD), N2 adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g−1 × h−1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diﬀuse reﬂectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.

Highlights

Owing to increasingly stringent environmental regulations, the development of materials with high activity as three-way catalysts (TWCs) for removing CO becomes necessary
The flame spray pyrolysis (FSP) method was used for synthesis of CuO-CeO2 mixed oxide catalysts with different nominal CuO to CeO2 mass concentration of 1, 5, 9, 14 and 17 wt %
With the introduction of copper species, the crystallite sizes of the samples become larger stemming from the presence of foreign dopants during the high-temperature particle formation in the FSP process leading to the thermal sintering effect [17]

Summary

Introduction

Owing to increasingly stringent environmental regulations, the development of materials with high activity as three-way catalysts (TWCs) for removing CO becomes necessary. The traditional supported noble metal catalysts (e.g., Pt, Pd and Rh) offer excellent catalytic properties with the low CO oxidation temperature. It is limited for their application due to the cost, easy sintering and coking [1]. Research has focused on the metal oxides for their economy and readily controlling activities [2,3]. The combination of copper oxides (CuOx ) and CeO2 is of great interest as a result of their cooperative redox and catalytic activities [4,5]. The activity of CuOx /CeO2 catalysts is related to the highly dispersed CuOx species, its strong interaction with

Methods

Results

Conclusion