Au/TiO2(P25)-gC3N4 composites with low gC3N4 content enhance TiO2 sensitization for remarkable H2 production from water under visible-light irradiation

A series of ternary Au/TiO2(P25)-gC3N4 heterostructure photocatalysts with low Au nanoparticle (NP) loading and gC3N4 content were synthesized and evaluated for H2 production from water with a very low amount of sacrificial agent (1 vol%) under solar and visible-light irradiation. The optimized composite, 0.3 wt% Au/TiO2(P25)-gC3N4 (95–5), exhibited a remarkable production rate under visible light (419 μmol−1 h−1 gcatalyst of H2), corresponding to almost twice the cumulated H2 production over 2.5 h as that of the Au/TiO2 (P25) reference. To best of our knowledge, this high of a yield has never been reported for comparable experimental conditions. The highest performing composite was characterized using UV–vis, XPS, UPS, BET, TEM, and TRMC techniques. The performance of the photocatalyst could be correlated to contributions of various phenomena such as effective heterojunction formation of TiO2 with gC3N4 operating in a Z-scheme dynamic allowing TiO2 photosensitization towards visible-light, also leading to new electronic hybrid states, and plasmonic Au/support Schottky junction allowing electronic trapping sites and co-catalytic effects. These contributions resulted in more efficient light harvesting and separation of the charge carriers to enhance visible light driven activity. [Display omitted] •0.3 wt. % Au/TiO2(P25)-gC3N4 (95–5) exhibits the highest H2 yield, 419 μmol−1 h−1 gcatalyst under visible-light.•A small gC3N4 content (5 wt.%) serves to effectively photosensitize TiO2(P25) to the visible-light, supported by TRMC.•Z-scheme heterojunction TiO2(P25)-gC3N4 improved remarkably charge carriers separation and transfer.•Schottky junction of Au/ TiO2(P25)-gC3N4 yield high-quality contact due to homogeneous surface coverage and small size NPs.•Very low quantities of both Au NPs loading and sacrificial agent are used.