Photocatalysis of bifunctional Cr- and Fe-doped CeO2 nanoparticles toward selective oxidation of 5-hydroxymethylfurfural and decomposition of high-density polyethylene

Abstract Oxygen vacancies (Vo) present in CeO2 nanoparticles (NPs) can effectively boost their photocatalytic activity under ultraviolet (UV) light. To improve photocatalytic performance, Cr- and Fe-doped CeO2 NPs with increased Vo were prepared using a simple method of doping Cr and Fe ions into CeO2 NPs, which was confirmed by an in-depth analysis of the structural and electronic changes. Through photocatalytic degradation (PCD) experiments with 5-hydroxymethylfurfural (HMF), we found that the PCD rates of the two doped CeO2 NPs were approximately 1.6 times faster than that of the CeO2 NPs. In addition, the conversion of HMF to 2,5-furandicarboxylic acid (FDCA) using the doped CeO2 NPs occurred only through the mechanism of the selective oxidation to 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), with a conversion efficiency of 40%, exhibiting approximately 3.7 times better efficiency than using CeO2 NPs. Furthermore, we confirmed that the photocatalytic reaction with the two doped CeO2 NPs leads to the degradation of high-density polyethylene (HDPE) through C-H bond breakage in the polymer backbone of HDPE, resulting in the doped CeO2 NPs enhancing the decomposition rate of HDPE microplastics by more than 1.7 times compared to CeO2 NPs.