TiO 2 interpenetrating networks decorated with SnO 2 nanocrystals: enhanced activity of selective catalytic reduction of NO with NH 3 † Minjun Chen,‡ a Jianping Yang,‡ ab Yong Liu, c Wei Li, c Jianwei Fan, * ac Xianqiang Ran, a Wei Teng, a Yu Sun, d Wei-xian Zhang, a Guangming Li, * a Shi Xue Dou b and Dongyuan Zhao c Highly branched TiO 2 interpenetrating network architectures deco- rated with SnO 2 nanocrystals were fabricated through a sacrificial- template approach for selective catalytic reduction of NO with ammonia. Such unique architectures demonstrate outstanding cata- lytic activity for NO conversion (90%), high N 2 selectivity (100%), good stability and strong resistance to SO 2 and H 2 O poisoning over a broad temperature range (75–325  C). 1. Introduction Nitrogen oxides (NO x ) are major precursors to the formation of photochemical smog, acid rain, and ozone holes. 1 Selective catalytic reduction (SCR) of NO x with ammonia in the presence of oxygen is an effective and most widely used technology for the removal of NO x from stationary and mobile sources. 2,3 At present, the common catalysts for SCR are V 2 O 5 /TiO 2 compos- ites promoted with WO 3 or MoO 3 . 4–7 Although considerable efforts have been made to develop metal oxide composites as SCR catalysts, a key shortcoming for large-scale industrial applications is the relatively high operating temperature (e.g., 300–400  C) for most SCR catalysts. 8,9 Therefore, it is highly desirable to develop efficient catalysts for low-temperature SCR. To overcome this drawback, a variety of catalysts and supports have been synthesized for low-temperature SCR. Previous reports have demonstrated that some metal oxide composites present high catalytic activity for SCR. 10–12 For example, SnO 2 -modied metal oxide catalysts show promising advantages for practical applications in the removal of NO x at low-temperatures and in the presence of SO 2 . 13,14 As a matter of fact, Sn 4+ presents the strong Lewis acidity, which favors chemical adsorption of NH 3 on the surface and forms the NH 3 –Sn bond. 15 Moreover, it should be pointed out that the high surface area of SnO 2 -doped metal oxide catalysts is bene- cial for enhanced catalytic activity. 16 On the other hand, TiO 2 , 17,18 ZrO 2 , 19 Al 2 O 3 (ref. 20) and SiO 2 (ref. 2) are also considered as the supports due to the high surface area, stability and environmentally benign properties. Among metal oxides, anatase TiO 2 with excellent dispersity and good resis- tance to SO 2 poisoning is regarded as the best support material for NO abatement. 21,22 Specically, it is found that the morphologies of TiO 2 supports are critical to the catalytic activity of metal oxide-doped TiO 2 . 23 Interpenetrating networks with dendritic interlaced structures can offer highly branched joints, vast approachable surface areas and reactive sites. Such unique features provide a signicant platform to design metal oxide composites for highly efficient catalysis and energy storage. Nonetheless, until now, there have been few reports on the synthesis of SnO 2 nanocrystal decorated TiO 2 inter- penetrating network structures. Reports on using SnO 2 -doped TiO 2 for SCR of NO and presenting high activity over a broad temperature range are also limited. In this work, we demonstrate an efficient sacricial-template approach for constructing anatase TiO 2 interpenetrating network architectures with highly branched structure and large specic surface area. By this approach, TiCl 4 pre-seeded SiO 2 opals are utilized as the template and TiF 4 aqueous solution as titanium species under hydrothermal treatment, and the TiO 2 interpenetrating network architectures are nally obtained aer reacting and selective etching of SiO 2 opals in NaOH aqueous solution. Additionally, SnO 2 nanocrystals can be decorated into the TiO 2 interpenetrating network architectures with unchanged morphology, mesoporous structure and high a College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, P. R. China. E-mail: fanjianwei@tongji.edu.cn; ligm@tongji.edu.cn; Tel: +86-21-65982658 b Institute for Superconducting & Electronic Materials, Australian Institute of Innovative Materials, University of Wollongong, Innovation Campus, Squires Way, North Wollongong, NSW 2500, Australia c Department of Chemistry, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, P. R. China d Shanghai Tongji Clearon Environmental-Protection Equipment Engineering Co., Ltd, Shanghai 200092, P. R. China † Electronic supplementary information (ESI) available. See DOI: 10.1039/c4ta05503a ‡ These authors contributed equally to this work. Cite this: DOI: 10.1039/c4ta05503a Received 15th October 2014 Accepted 1st December 2014 DOI: 10.1039/c4ta05503a www.rsc.org/MaterialsA This journal is © The Royal Society of Chemistry 2015 J. Mater. Chem. A Journal of Materials Chemistry A COMMUNICATION Published on 01 December 2014. Downloaded by University of Wollongong on 11/12/2014 06:14:00. 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