Sulfated CeO2-TiO2 as H2 evolution photocatalyst: Synergic effects of heterojunction and sulfation on catalyst performance

• The heterojunction between CeO 2 and TiO 2 was achieved by sol-gel method. • Acid treatment introduced brønsted acid sites and lewis acid sites on the surface of CeO 2 -TiO 2 composites. • Lewis acid sites promoted the separation of the photogenerated carriers . • Brønsted acid sites enhanced H 2 O adsorption and provided protons for photocatalytic H 2 production. • The high photocatalytic H 2 -evolution performance was ascribed to the synergetic effects of heterojunction and acid impregnation. SO 4 2− /CeO 2 /TiO 2 composite oxides are successfully fabricated via sol-gel method and impregnation process for photocatalytic H 2 production. The characterization results from XRD, FTIR and TEM revealed that the heterojunctions were formed by the formation of Ti-O-Ce bond across the SO 4 2− /CeO 2 /TiO 2 interface, which was contributed significantly to separation of photo-generated carriers. Py-FTIR spectra and XPS results indicated that Lewis acid and Brønsted acid sites were formed over the surface of SO 4 2− /CeO 2 /TiO 2 composite, which was owing to SO 4 2− coordinated to the metal on the sample surface. The induced Lewis acid sites could enhance the separation of photogenerated carriers, and Brønsted acid sites could provide protons for photocatalytic H 2 production. In addition, the Lewis acidity could facilitate the shift of conduction band minimum to a more negative value, which improves the photocatalytic H 2 production capacity of SO 4 2− /CeO 2 /TiO 2 . The results of photocatalytic H 2 production revealed that SO 4 2− /CeO 2 /TiO 2 composite exhibits superior photocatalytic activity compared to bare CeO 2 , TiO 2 and CeO 2 -TiO 2 composite. Notably, it achieves the average H 2 yield rate of 6295.2 μmol· g −1 h −1 over a period of 5 h. Combine the results of spectra analysis and photocatalytic activity H 2 evolution, it can be concluded that the synergetic effects of heterojunction structure of CeO 2 /TiO 2 composite and acid impregnation promoted the photocatalyst activity.