Feature ArticleFacile synthesis of tube-shaped Mn-Ni-Ti solid solution and preferable Langmuir-Hinshelwood mechanism for selective catalytic reduction of NOx by NH3

•A self-templated Mn-Ni-Ti tube-shaped solid solution is fabricated.•Strcuture defect of materials is adjusted by the Mn/Ni/Ti ratio.•Mn/Ni co-decoration leads to the weakened competitive adsorption of NH3 with NO.•L-H mechanism is the preferential pathway for N2 generation.

We present a tube-shaped Mn-Ni-Ti solid solution for the selective catalytic reduction of NOx with NH3 (NH3-SCR) through a facile self-templated urea-homogeneous precipitation method, which leads to the fine dispersion of the MnOx and NiOx active species in the TiO2 lattice. The ratio of Mn/Ni/Ti is an important factor to affect the crystallinity of Mn-Ni-Ti solid sulotion, and the catalyst with a Mn/Ni/Ti ratio of 2/3/5 (Mn2-Ni3) exhibits the significant structure distortion. The abundant surface defects induce more generation of Mn4+ species, surface adsorbed oxygen and Lewis acid sites, and acclerate the adsorption and activation of NO molecules. The appropriate Mn/Ni ratio inhibits the competitive adsorption of NH3 with NO, and facilitates the Langmuir-Hinshelwood (L-H) mechanism to form N2, which acts as a much more rapid pathway in comparison to the parallel one following Eley-Rideal (E-R) mechanism. The readily occurence of L-H mechanism significantly improves the SCR performance of catalyst.

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