Efficient photocatalytic oxygen activation by oxygen-vacancy-rich CeO2-based heterojunctions: Synergistic effect of photoexcited electrons transfer and oxygen chemisorption

Photocatalytic molecular O2 activation has a broad prospect for generation of reactive oxygen species, but many of these conversions are unsatisfactory due to the poor oxygen adsorption capacity and low carrier utilization. To solve these problems, oxygen-vacancy-rich CeO2-based heterojunctions were constructed to improve oxygen chemisorption and photoexcited electrons transfer. The results of X-ray photoelectron spectroscopy, Raman and electron paramagnetic resonance tests suggested that there were abundant oxygen vacancies on the surface of the CeO2, which can act as oxygen adsorption sites to accelerate the chemisorption of O2. Density functional theory (DFT) calculations, electrochemical and photochemical analyses proved that photogenerated electrons transferred from AgI to CeO2 on the AgI/CeO2 heterojunction interface, which inhibited the recombination of charge carriers and thus generated more electrons to facilitate the activation of O2. Profiting from the excellent photocatalytic oxygen activation performance, the pseudo-first-order degradation kinetics constant of tetracycline by the AgI(5%)/CeO2 was about 3 times and 47 times higher than that of CeO2 and AgI, respectively. And AgI(5%)/CeO2 can completely inactivate Escherichia coli (E. coli) within 8 min under visible light irradiation. Moreover, we also explored the degradation pathway of tetracycline and the inactivation mechanism of E. coli. This work is expected to inspire more wonderful research on improving the molecular O2 activation efficiency from different aspects.