Solar light sensitized p-Ag2O/n-TiO2 nanotubes heterojunction photocatalysts for enhanced hydrogen production in aqueous-glycerol solution

•Biphasic TiO2 nanostructures were prepared by using hydrothermal and thermal treatment methods.•p-Ag2O/n-TiO2 nanotubes heterojunction govern the improved photocatalytic properties.•Ag2O loaded TiO2 nanotubes produced 26 folds higher H2 production in glycerol solution.•Photocatalytic activity was compared in summer and winter season.

Solar light harvesting nano-heterojunction p-Ag2O/n-TiO2 nanotube catalysts were successfully synthesized by a combination of hydrothermal and wet impregnation methods. The crystal structure and surface morphology analysis revealed that n-TiO2 composed of biphasic anatase-rutile with nano-tubular morphology. The X-ray photoelectron spectrum confirmed the presence of Ti4+ and Ag+ in the form of TiO2 and Ag2O, the results are in good agreement with TEM images. Moreover, DRS UV-Vis spectra and photocurrent density measurements indicated that Ag2O/TiO2 nanotubes have shown strong absorption in visible region and improved current production that indicates the hetero-junction properties. The Ag2O loaded (0.5–2.0 wt%) TiO2 nanotubes showed 26 folds enhanced photocatalytic hydrogen (H2) production in glycerol/water mixture than the standard TiO2 P-25 under solar light irradiation. Interestingly, the catalytic recyclability tests carried out in pure water and glycerol/water mixture exhibited similar rate of H2 production without significant loss in catalytic activity. Furthermore, the photocatalytic activity conducted in summer season exhibited higher rate of H2 production than the experiments conducted during winter season owing to the variation in solar flux. The high rate of H2 production can be attributed to the synergistic functions of 1-D nano-tubular morphology, hetero-junction formed between biphasic TiO2 photocatalyst and visible light active Ag2O as sensitizer. Based on the experimental results, a possible electron-hole transfer mechanism was also proposed.

Graphical abstractNano-heterojunction of Ag2O/TiO2 nanotubes photocatalyst absorbed solar light in UV and visible region results in generation of charge carriers both at valence and conduction band level. The photogenerated charge carriers migrated to the catalyst surface and involve in red-ox reaction produces H2, oxidation of water and glycerol results in H+, intermediates and CO2.Figure optionsDownload full-size imageDownload as PowerPoint slide