Mild generation of surface oxygen vacancy on CeO2 for improved CO2 photoreduction activity.
The vacancy defects of semiconductor photocatalysts play a key role in enhancing their photocatalytic CO2 reduction activity. In this work, CeO2 was chosen as a model catalyst and oxygen vacancy was introduced at its surface by facile and mild oxalic acid treatment followed by moderate heating in N2. Such a treatment resulted in much increased ratio of Ce3+/Ce4+ in CeO2, and the oxygen vacancy-enriched CeO2 showed remarkably enhanced photocatalytic activity in CO2 reduction, with CO being the dominant reduction product, of which the yield was about 8 times that on the pristine CeO2. In-situ FT-IR spectra showed that carbonates strongly adsorbed on the photocatalyst surface might be the main obstacle to maintaining the high CO2 reduction activity and stability of CeO2 with O vacancy.