Co single atoms and CoO clusters over nitrogen–doped hollow carbon spheres for synergistic oxidation of aromatic alkanes

Single atom catalysts have attracted mountainous attentions in the field of catalysis, owing to their unsaturated coordination environment and maximized utilization of metal atoms. However, single atom catalysts may suffer from low catalytic efficiency toward multistep reactions because of the single active site. Herein, we report a synergistic catalyst (n–Co/CoO@N–HMCS) to solve above problem through supporting Co single atoms (Co–SAs) and CoO clusters (CoO–CTs) on nitrogen–doped hollow carbon spheres for selective oxidation of aromatic alkanes. Among the as–prepared catalysts, 0.03–Co/CoO@N–HMCS exhibits the remarkable catalytic performance, with 96.6% conversion of ethylbenzene and 99.5% selectivity to acetophenone. Density functional theory calculation demonstrates that the synergistic effect between Co single atoms and CoO clusters significantly decreases the energy barrier of cleavage of the C–H bond of ethylbenzene, a rate–determining step for the oxidation of ethylbenzene, so that to accelerate the conversion of ethylbenzene into acetophenone. The strategy is applicable for oxidation of other aromatic alkanes as well.