Morphology control of Co3O4/CeO2 heterojunctions toward efficient peroxymonosulfate activation for trichloroethylene removal: Effect of oxygen precursors

In this study, a series of X-Co3O4/CeO2 heterostructure was successfully synthesized through sol-gel followed by calcination and was utilized for the highly efficient activation of peroxymonosulfate (PMS) for degrading trichloroethylene (TCE) in aqueous solutions. The effect of different oxygen precursors (e.g. citric acid, barbituric acid and oxalic acid) on the catalytic efficacy of Co3O4/CeO2 was comprehensively investigated. The CA-Co3O4/CeO2 composites synthesized using citric acid as the oxygen precursor featured an abundance of through-hole structures and oxygen vacancies, which served as catalytic sites for the activation of PMS and the subsequent degradation of TCE. Concurrently, the fully exposed Ce/Co bimetallic particles demonstrated substantial synergistic catalytic activity. The combination of 0.1 g/L CA-Co3O4/CeO2 and 0.5 mM PMS resulted in the removal of 97.5 % of TCE; under identical conditions, only 91.3 % and 85.4 % of TCE were removed using BA-Co3O4/CeO2/PMS and OA-Co3O4/CeO2/PMS systems, respectively. However, all were significantly better than the Co3O4/PMS and CeO2/PMS systems. The valence conversion between Ce(III) and Ce(IV) on the catalyst surface acts as an electron donor, enhancing the catalytic activity of active cobalt species, with Ce-O-Co serving as an electron channel to accelerate the process. Quenching experiments and electron spin resonance experiments show that the removal of TCE in the oxidized system proceeds via a dual-track pathway of radicals and non-radicals. Furthermore, the CA-Co3O4/CeO2/PMS oxidation system demonstrated broad pH stability and significant tolerance to aqueous environments. This study offers novel strategies for the morphological design of cobalt oxides and their varied applications in advanced oxidation processes. [Display omitted] •Different oxygen precursors can effectively affect the intrinsic structure of Co3O4/CeO2 and further influence its catalytic activity.•The cheese-like porous architecture in CA-Co3O4/CeO2 provides domain-limited access for its activation of PMS and degradation of TCE.•The CA-Co3O4/CeO2/PMS system exhibits exceptional environmental adaptability and degrades TCE by radical and non-radical pathways.