Fabricated S-scheme CoS/CeO2 heterojunction photocatalyst efficiently activates peroxymonosulfate for polyethylene terephthalate plastic degradation: Insight into radicals and electron transfer

Polyethylene terephthalate (PET) plastics are widely utilized, yet they also give rise to significant environmental contamination. In this study, a CoS/CeO2 material with an S-scheme heterojunction was constructed using CoS with CeO2 derived from MOFs and employed for the photocatalytic activation of peroxomonosulfate (PMS) for the degradation of PET. The CoS/CeO2/vis/PMS system demonstrated a degradation rate of up to 95.75 % (weight loss rate) for PET plastic. The performance of this system is much better than that of simple photocatalytic or PMS systems. Photogenerated carriers generated by heterojunctions upon illumination accelerate the fast electron cycling of Co2+/Co3+ through the S-scheme transfer pathway driven by a directional interfacial electric field. This promoted efficient mass transfer in the inhomogeneous phase system (such as SO4 center dot- , e-) and acted as an adsorption activation site for PMS. In-situ X-ray photoelectron spectroscopy (In-situ XPS) and ESR test proved that the electron flow in the heterojunction conforms to the S-scheme mechanism. Density functional theory (DFT) calculations revealed the material of the CoS/CeO2 interface and the successful construction of the modulated electronic structure led to the accumulation of holes on CeO2 and electrons on CoS. Bader analysis on charge density distribution further demonstrated that the formation of the heterojunction decreased the adsorption energy of the PMS on the Co sites, which in turn lowered the energy barrier for the generation of SO4 center dot- . This work would provide a novel solution to the problem of removing plastic pollutants from water, as well as new insight into the construction of S-scheme heterojunctions and the mechanism of photocatalytic PMS activation.