Enhanced photocatalytic hydrogen production on Au/TiO2-CeO2 through the formation of oxygen vacancies

TiO 2 -CeO 2 (TC) materials superficially modified with Au nanoparticles (AuNPs) were prepared using the sequential deposition-precipitation with urea method. EDS revealed the effective deposition of Ce and Au and a well-distributed CeO 2 phase on TiO 2 . STEM-HAADF showed proximity between the TiO 2 and CeO 2 phases and the formation of AuNPs with a size of 3.6 ± 0.7 nm. The TiO 2 band gap (E g ) decreased slightly with the increase in the CeO 2 concentration. For the TC materials, XPS confirmed a slight increase in the Ti 3+ concentration and the predominant presence of Ce 3+ , which increased the oxygen vacancies (OVs). Furthermore, the AuNPs were mainly composed of Au 0 (80.2 %). XPS and photoelectrochemical characterizations revealed higher valence band-edge energy after the CeO 2 and AuNP incorporation, making proton reduction in the material more thermodynamically favorable. As for the hydrogen evolution reaction, the TC material with optimal Ce loading of 0.9 wt% increased the photocatalytic hydrogen production rate to 2.3 mmol g −1 h −1 , 20 % higher than that of pristine TiO 2 . Additionally, adding 0.7 wt% of AuNPs led to a substantial improvement in hydrogen photocatalytic production, reaching 10.7 mmol g −1 h −1 . This enhancement was ascribed to the ability of AuNPs to act as electron traps, reducing the electron-hole recombination. Photoelectrochemical characterization showed a decrease in the flat-band potential upon incorporation of CeO 2 and AuNPs, which could also be associated with the formation of OVs. AuNPs on the surface improved the stability of the electrons in the CB through the formation of a Schottky junction. • Au/TiO 2 -CeO 2 samples were prepared by sequential deposition-precipitation with urea. • TiO 2 -CeO 2 materials showed a decrease in band gap values compared to bare TiO 2 . • Optimal amount of oxygen vacancies related to Ce 3+ formation enhanced photoactivity. • Increase in the conduction band energy-edge produced a favored proton reduction. • AuNPs increased photoactivity by stabilizing electrons in the conduction band.