Modulating the Dispersion of Ce on CeO<sub>2</sub>/TiO<sub>2</sub> Catalysts for Efficient NH<sub>3</sub>–SCR of NO
Nan Jiang, Jiawei Yang, Yirui Yang, Gao Hui Wu, Kaili Ma, Xiuwen Wang, Qiuhui Qian, Qing Tong, Wei Tan, Lin Dong
Abstract
CeO 2 –TiO 2 catalysts have been intensively investigated for their promising application prospect in the selective catalytic reduction of NO by NH 3 (NH 3 –SCR of NO). However, the optimal dispersion of CeO 2 on CeO 2 –TiO 2 catalysts is still controversial. In this work, using TiO(OH) 2 and TiO 2 as supports and different Ce precursors, TiO 2 -supported CeO 2 with a controllable dispersion was prepared. It was uncovered that hydroxyl groups on TiO(OH) 2 could facilitate the even dispersion of Ce (high dispersion, Ce/Ti–H), while the impregnation of cerium oxalate onto TiO 2 would result in the generation of highly crystalline CeO 2 (low dispersion, Ce/Ti-L), even with a low CeO 2 loading of 5 wt %. When cerium nitrates were impregnated onto TiO 2, slightly crystalline CeO 2 (moderate dispersion, Ce/Ti-M) was successfully fabricated. The NH 3 –SCR activity on the prepared CeO 2 /TiO 2 catalysts followed an order of Ce/Ti-M > Ce/Ti–H > Ce/Ti-L, suggesting that small CeO 2 particles on TiO 2 could better facilitate the proceeding of the NH 3 –SCR reaction. According to the results of the mechanism study, the superior redox capability of Ce/Ti-M enabled efficient activation of reactants, thus achieving the best NH 3 –SCR activity. This study provided a strategic framework for the design of high-performance catalysts by precisely engineering the dispersion of active species at the nanoscale.