Charge-redistribution-induced new active sites on (0 0 1) facets of Α-Mn₂O₃ for significantly enhanced selective catalytic reduction of NO_x by NH₃

Crystal facets usually play an important role in the catalytic activity of inorganic single crystals. In this work, two α-Mn₂O₃ single crystals with an octahedron (exposed with (1 1 1) facet) and a truncated octahedron (exposed with both (1 1 1) and (0 0 1) facets) were successfully prepared by a simple solvent-thermal reaction, and their catalytic activities were evaluated by the selective catalytic reduction (SCR) of NO_x with NH₃. The results show that the catalytic performance of the α-Mn₂O₃ single crystal with a truncated octahedron was enhanced in comparison with the α-Mn₂O₃ single crystal with an octahedron by the exposure of a small fraction of (0 0 1) facets. This can be attributed to the new active sites created by charge redistribution on the surface of the (0 0 1) facets, which provides more adsorption sites, facilitating the further adsorption and reaction of NH₃ and NO molecules, and thereby enhancing the catalytic performance. This work should provide new insight into the understanding of crystal-facet-dependent reactivity and important guides for the design and preparation of SCR catalysts with high activity.