Architecturing CoTiO3 overlayer on nanosheets-assembled hierarchical TiO2 nanospheres as a highly active and robust catalyst for peroxymonosulfate activation and metronidazole degradation

Catalytic performance of a heterogeneous cobalt-based catalyst for advanced oxidative process (AOP) correlates tightly with its structure and composition. The main objective of this study is to maximize the utilization and accessibility of cobalt sites while enhancing their activity and stability through rational structural and composition designs, and thus to achieve an excellent performance for heterogeneous peroxymonosulfate (PMS) activation. To this end, a novel CoTiO 3 /TiO 2 composite (CTT), composed of CoTiO 3 overlayer on nanosheets-assembled hierarchical TiO 2 nanospheres, was elaborately designed and synthesized. The resulting CTT possessed certain features including CoTiO 3 -rich surface, large surface area (114.8 m 2  g −1 ), and highly open porous channels, which afforded sufficient accessible active sites against undesirable particle agglomeration and shedding. Moreover, cobalt sites of CTT exhibited a higher activity toward PMS than those of Co 3 O 4 due to the composition-induced distinct adsorption nature, easy electron transfer, and strong bond-weakening ability. Benefitting from the unique combination of structural and compositional advantages, CTT manifested remarkable catalytic efficiency, low cobalt leaching (0.078 mg L −1 ), and excellent reusability in activation of PMS for degradation of the emerging antibiotic pollutant metronidazole (MNZ). The potential degradation pathway for MNZ and the catalytic mechanism were further elucidated. The design strategy proposed in this study may provide a new opportunity for future development of high-performance heterogeneous cobalt-based catalysts in remediation of aquatic environment.