Fabricating yolk–shell structured CoTiO3@Co3O4 nanoreactor via a simple self-template method toward high-performance peroxymonosulfate activation and organic pollutant degradation

As one of the newly emerging heterogenous catalysts for peroxymonosulfate (PMS) activation, complex hollow structured nanoreactors with multilevel interiors can significantly enhance the catalytic performance and manifest great potentiality in organic pollutant degradation. Herein, a novel yolk–shell structured CoTiO3@Co3O4 nanoreactor was synthesized via a simple self-template method using amorphous TiO2 nanospheres as template and CoCl2·6H2O as cobalt source, respectively. Owing to the remarkable structural advantages and unique space confined effect, the as-synthesized CoTiO3@Co3O4 nanoreactor exhibited a high efficiency for PMS activation, enabling 100% removal of rhodamine B (RhB; 50 mg L−1) in a short period of time, with a rate constant (0.1993 min−1) much higher relative to those of CoTiO3 (0.0246 min−1) and Co3O4 (0.0150 min−1). Moreover, this catalyst showed a low cobalt leaching (0.080 mg L−1) while keeping almost unchanged catalytic activity in the cyclic degradation processes. Based on ESR analysis and quenching experiments, the possible catalytic mechanism was proposed. The mineralization degree was found to be 79.5% in the RhB degradation process via TOC analysis. LC/MS was employed to identify the intermediates and corresponding degradation pathway was elucidated. Besides, CoTiO3@Co3O4 nanoreactor was revealed to be also highly efficient in activating PMS for degradation of several other recalcitrant organic pollutants. This work may be suggestive to the design and synthesis of advanced complex hollow nanoreactors for environmental remediation.