Revealing the crystal phase effect of CeO2 in spinel-based nanocatalysts toward the peroxymonosulfate activation for organics degradation

The composite catalysts with different morphologies (nanorods, nanocubes, nano-polyhedra and nanosphere) of ceria as loadings are prepared by using spinel as the carrier to investigate the crystal plane effect of ceria on the formation of oxygen vacancies in the catalyst and the activation efficiency of peroxymonosulfate (PMS). The results show that the CeO2 nanocubic-based composite (CFOC-C) with more (1 0 0) crystal phase has superior catalytic performance in each individual condition, providing rapid activation of PMS and pollutant degradation. Through characterizations, the largest oxygen vacancy concentration is observed on the CFOC-C surface and the strongest reactive oxygen detection signal is obtained in the CFOC-C/PMS system. Moreover, the more active (1 0 0) crystal phase on the CeO2 surface promotes the electron delocalization at Ce sites, accelerating the adsorption of PMS molecules and the cleavage of O-O bonds, subsequently generating more active species. With levofloxacin as the target, the main degradation intermediates and the degradation pathways in the CFOC-C/PMS system are analyzed in detail. The toxicity estimation results suggest that the toxicity of the degradation products decreases progressively with the reaction.