Selective Cl-Decoration on Nanocrystal Facets of Hematite for High-Efficiency Catalytic Oxidation of Cyclohexane: Identification of the Newly Formed Cl–O as Active Sites

Understanding the structure–reactivity relationship at the atomic scale is of great theoretical importance for rational design of highly active catalysts, which has long been a central concern in catalysis communities and interface science. Herein, we developed a high-efficiency catalyst for catalytic oxidation of C6H12 by poststructural decoration on well-defined single-crystal facets of hematite. Especially for Cl-decorated {012} facets, the conversion and KA oil selectivity are improved about 3.4 times and 2 times, respectively. A better catalytic performance of the newly formed active site is derived from the charge difference between Cl and the neighboring outmost O atoms, which is affected by the geometric and electronic structures of the original catalyst surface. Based on the experimental results and the theoretical analysis, we concluded that the contribution of various O terminations to Cl-decoration follows the order O(I) > O(III) > O(II). Cl-decorated {001} facets show the highest intrinsic activity, whereas Cl-decorated {012} facets show the best catalytic performance because of their more active sites for Cl-decoration.