Experimental and first-principles DFT study on oxygen vacancies on cerium dioxide and its effect on enhanced photocatalytic hydrogen production

• Oxygen vacancies create Ce (III) to shorten the band gap and enhance the visible light absorption.
• (111) plane is a superior position to enhance photocatalytic activity.
• Oxygen vacancies and Ce (III) on the surface affects the band gap.
• Cerium dioxide calcined under 400 °C shows superior photocatalytic activity.

Experimental and computational (DFT) approaches were carried out to investigate oxygen vacancies on cerium dioxide. Computational result indicates oxygen vacancies can shorten the band gap of CeO2 and enhance the absorption for visible light because Ce (III) created by generation of oxygen vacancies is easier for excitation than Ce (IV) under same irradiation. The order of calculated band gap for Ce16O31, (111) < (113) < (133), and the absorption data suggests that (111) plane may be the most ideal position for oxygen vacancies to enhance photocatalytic activity. The result has been tested and verified by experimental study, including UV–Vis spectra, XPS, XRD and PL. The enhanced hydrogen productions of CeO2 samples, from 34.8 μmol to 63.0 μmol, are 2.0–3.5 times as high as that of commercial CeO2 (17.8 μmol).