Theoretical guidance and experimental confirmation on catalytic tendency of M-CeO₂ (M = Zr, Mn, Ru or Cu) for NH₃-SCR of NO

Abstract

Herein, we demonstrate that the degrees of catalytic performance of M-CeO₂-based catalysts (M=Mn, Cu, Ru or Zr) for an ammonia selective catalytic reduction (NH₃-SCR) of nitric-oxide (NO) can be estimated using three theoretical terms; (i) an oxygen vacancy formation energy of a catalyst, (ii) an adsorption energy of NO and (iii) an adsorption energy of NH₃. Those terms predict the trend of the catalytic performance as the order; Mn–CeO₂ > Cu–CeO₂ > Ru–CeO₂ > Zr–CeO₂ > CeO₂. To verify the theoretical prediction, the catalysts were synthesized and tested their performances on the NH₃-SCR of NO reaction. The normalized NO conversion rates at low temperatures (100–200 °C) were measured for Mn–CeO₂, Cu–CeO₂, Ru–CeO₂, Zr–CeO₂ and CeO₂ as 2.61–7.46, 1.30–6.82, 0.73–3.02, 0.81–3.31 and 1.55–2.33 mol s⁻¹ m⁻², respectively. In addition, a concept of a structure-activity relationship analysis shows a strong relationship between theoretical and experimental results. Consequently, an application of predicting the catalytic performance of catalysts from theoretical calculations prior the catalyst synthesis is useful in catalyst design and screening that can reduce time and cost.

Keywords:

• DFT
• cerium oxide
• nitrogen oxide
• energy-activity relationship, decomposition

Acknowledgment

P.M. would like to thank the National Natural Science Foundation of China (NSFC) Research Fund for International Young Scientists FY 2016 (21650110450). The authors acknowledge the support of the National Basic Research Program of China (973 Program, 2014CB660803) and the Shanghai Municipal Education Commission (14ZZ097) and the Professional and Technical Service Platform for Designing and Manufacturing of Advanced Composite Materials (Shanghai) 16DZ2292100. All calculations were done at Nanoscale simulation laboratory, National Nanotechnology Center (NANOTEC), Thailand.