Mn Co Mixed Oxide Nanosheets Vertically Anchored on H 2 Ti 3 O 7 Nanowires: Full Exposure of Active Components Results in Significantly Enhanced Catalytic Performance Jian-Wen Shi,* [a] Zhaoyang Fan, [a] Chen Gao, [a] Ge Gao, [a] Baorui Wang, [a] Yao Wang, [a] Chi He,* [b] and Chunming Niu [a] 1. Introduction Nitrogen oxides (NO x , x = 1,2) emitted from the combustion of fossil fuels are attracting more and more concern because of their serious negative effects on the atmosphere, such as acid rain, photochemical smog, greenhouse effect, and ozone de- pletion. [1, 2] Selective catalytic reduction (SCR) with NH 3 is con- sidered as the state-of-the-art technology to eliminate NO x emissions from coal-fired power plants. [3, 4] As the commercial- ized catalysts, V 2 O 5 -WO 3 (MoO 3 )/TiO 2 has remained the most ef- fective in the last few decades. [5, 6] However, the narrow opera- tion temperature window (300–400 8C) and the toxicity of V 2 O 5 bring about increasing concerns about not only energy con- sumption but also environmental pollution. [7, 8] Thus, more and more researchers have shifted their focus to the development of low-temperature vanadium-free de-NO x catalysts. [9–11] So far, numerous explorations have found that several transi- tion metal oxides (TMOs) show great potential to lower the re- action temperature and broaden the operation temperature window, among which the manganese oxides (MnO x ) remarka- bly outperform the others in terms of the low-temperature de- NO x performance and have environmental benign charac- ters. [12, 13] However, pure MnO x catalysts still suffer from serious challenges owing to the low surface area, poor water tolerance and thermal stability. Constructing MnO x -based composite oxides by mixing with the other metal oxides is considered as an effective strategy to overcome these shortcomings. Based on this, Mn-Ce, Mn-Fe, and Mn-Ti composite oxides have been developed for the SCR of NO x , and remarkable achievements have been made. [14–21] In recent years, Mn Co composite oxides have attracted considerable attention owing to their ex- cellent de-NO x performances. Moreover, it is well known that the morphology and structure of catalysts play an important role in their catalytic performance in addition to the desirable compositions. [22–24] Therefore, Mn Co composite oxides with different morphologies and structures, such as nanocages, [25] micro/nanospheres, [26–28] porous structures, [29] ordered mesopo- rous structures, [30] polyporous network structures, [31] have been successfully developed for the SCR of NO x . Even Mn Co com- posite oxides loaded on different supports, such as reduced graphene oxide (rGO), [32] TiO 2 , [33, 34] ZSM-5, [35] have also been ex- plored for the application of SCR de-NO x . From the view of taking full advantage of the active ingredient of the catalysts, The full exposure of active ingredients plays an important role in the enhancement of catalytic performance. In this work, a series of novel catalysts, Mn Co mixed oxide nanosheets with ultrathin thickness (about 3.5 nm) and different Mn/Co ratios (0.52, 0.69, and 1.52) vertically anchored on a support (H 2 Ti 3 O 7 nanowires), are rationally developed. This unique structure not only fully exposes the active ingredients of the Mn Co mixed oxides, but also is very favorable for the diffusion and transfer of gas molecules through the space between these standing nanosheets. As expected, the developed catalysts (MnO x -CoO y / H 2 Ti 3 O 7 , MnCoTi), especially MnCoTi-2 with the Mn/Co molar ratio of 0.69, present excellent low-temperature selective cata- lytic reduction (SCR) performance, high N 2 selectivity, superior water tolerance and stability. The relative turnover frequency (TOF) value over MnCoTi-2 at 100 8C is as high as 9.25  10 4 s 1 under the gas hourly space velocity (GHSV) of 200 000 h 1 , which is rarely reported among Mn-Ti, Mn Co, and Mn Co-Ti mixed oxide catalysts. The results of in situ diffuse reflectance infrared Fourier transform spectroscopy suggest that the coor- dinated NH 3 , NH 4 + ions, adsorbed NO 2 , and bidentate nitrate are the reactive species and the Eley–Rideal and Langmuir– Hinshelwood mechanisms can be simultaneously involved on the surface of the MnCoTi-2 at a relatively low temperature (90 8C). [a] Prof. Dr. J.-W. Shi, Z. Fan, C. Gao, G. Gao, B. Wang, Y. Wang, Prof. Dr. C. Niu Center of Nanomaterials for Renewable Energy State Key Laboratory of Electrical Insulation and Power Equipment School of Electrical Engineering Xi’an Jiaotong University Xi’an 710049 (P.R. China) E-mail : jianwen.shi@mail.xjtu.edu.cn [b] Prof. Dr. C. He Department of Environmental Science and Engineering School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 (P.R. China) E-mail : chi_he@xjtu.edu.cn Supporting Information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.org/10.1002/cctc.201800227. This manuscript is part of a Special Issue on the “Portuguese Conference on Catalysis” based on the International Symposium on Synthesis and Catalysis (ISySyCat). ChemCatChem 2018, 10, 2833 – 2844  2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 2833 Full Papers DOI: 10.1002/cctc.201800227