Oxygen clusters anchoring Co ions in hollow tungstic acid spheres to promote the generation of singlet oxygen for New Coccine degradation

In this study, distinctive hollow spheres assembled by interlaced tungstic acid nanosheets (H2WO4) are synthesized through a facile self-template method. Cobalt ions were strongly coordinated with the oxygen cluster in tungstic acid, successfully preparing the Co/H2WO4 composite for use as a peroxymonosulfate (PMS) activator. Owing to the synergistic effect between oxygen clusters and Co active component as well as the interlaced nanosheets-shells with hollow interior in Co/H2WO4, the composite exhibits appealing degradation performance, achieving 100% degradation of New Coccine (NC) in 40 min. The cavities from interconnected nanosheets and hollow interior can not only provide large areas for Co2+ loading, but also assist the significant improvement of reaction contact efficiency during the degradation processes. It was found that non-free radical of singlet oxygen (1O2) is the major reactive oxygen species playing a critical role in high-efficiency degradation of NC, comparing with generated hydroxyl radicals (center dot OH) and superoxide (O2 center dot-). The Co/H2WO4/PMS system also shows strong resistance to inorganic ions and pH during the degradation. This study offers a new strategy for effectively designing H2WO4 materials with novel morphological structure and provides a reference for designing highperformance catalyst in water treatment.