Enhanced Performance of Ceria-Based NO_x Reduction Catalysts by Optimal Support Effect

Abstract

CeO-based catalysts have attracted widespread attention in environmental-protection applications, including selective catalytic reduction (SCR) of NO by NH, and their catalytic performance is often intimately associated with the supports used. However, the issue of how to choose the supports of such catalysts still remains unresolved. Herein, we systematically study the support effect in SCR over CeO-based catalysts by using three representative supports, AlO, TiO, and hexagonal WO (HWO), with different acidic and redox properties. HWO, with both acidic and reducible properties, achieves an optimal support effect; that is, CeO/HWO exhibits higher catalytic activity than CeO supported on acidic AlO or reducible TiO. Transmission electron microscopy and X-ray diffraction techniques demonstrate that acidic supports (HWO and AlO) are favorable for the dispersion of CeO on their surfaces. X-ray photoelectron spectroscopy coupled with theoretical calculations reveals that reducible supports (HWO and TiO) facilitate strong electronic CeO-support interactions. Hence, the excellent catalytic performance of CeO/HWO is mainly ascribed to the high dispersion of CeO and the optimal electronic CeO-support interactions. This work shows that abundant Brønsted acid sites and excellent redox ability of supports are two critical requirements for the design of efficient CeO-based catalysts.

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