Postsynthetic incorporation of catalytically inert Al into Co3O4 for peroxymonosulfate activation and insight into the boosted catalytic performance

Herein, we reported postsynthetic incorporation of generally believed catalytically inert Al3+ ion into the lattice of commercial Co3O4 to form a series of Al doped Co3O4 (ACO) catalysts, and demonstrated that the Al incorporation with suitable concentration could induce a surprising boost in activation of peroxymonosulfate (PMS). Unlike conventional direct synthesis that might lead to the formation of bimetallic spinel oxides in an uncontrollable manner, the presented method could produce ACO catalysts with almost unchanged particle size and morphology, which was beneficial for a reliable assess on the composition-dependent catalytic performance to avoid possible misjudgment caused by other factors. More importantly, the Al incorporation could not only promote the adsorption affinity and electron transfer ability of Co to PMS but also facilitate the OO bond cleavage of the adsorbed PMS, thereby leading to an enhanced catalytic ability. As a result, the optimal ACO (Co2.98Al0.02O4) exhibited a high degradation efficiency with a rate constant (0.127 min−1) 2.6-folds that of pure Co3O4 (0.049 min−1) in PMS activation for degradation of metronidazole (MNZ). Besides, Co2.98Al0.02O4 manifested low cobalt leaching (≤79 μg L–1). Both degradation pathway and catalytic mechanism were proposed comprehensively, and the superb reusability of Co2.98Al0.02O4 was also confirmed. This study enriches the current synthesis methodology for bimetallic spinel oxides and provides new insights into inert metal-promoted heterogeneous cobalt-based catalysis for robust advanced oxidation processes.