Facile synthesis of g-C3N4/TiO2/CQDs/Au Z-scheme heterojunction composites for solar-driven efficient photocatalytic hydrogen

A simple strategy has been reported for the construction of Z-scheme heterojunction, using precious metal (Au)-carbon quantum dots (CQDs)-graphite carbonitride (g-C3N4)/titanium dioxide (TiO2) superposition. These components maximize the efficiency of resulted composite, including the local surface plasmonic resonance effect of the precious metal, the conversion photoluminescence (PL) characteristics of CQDs, and the doping characteristics of g-C3N4/TiO2 complementary materials. The composition, morphology, and photoelectric properties of the composites are characterized. It is found that the nano-Au particles and CQDs are evenly dispersed on g-C3N4/TiO2, and the composite material has effective e(-)/h(+) pairs separation, excellent electron transfer, reasonable band gap width, and good visible light utilization ability. Subsequently, the catalytic decomposition of water by the composites under the simulated solar drive exhibited excellent hydrogen production performance, which proves the effectiveness of our proposed material design strategy. Besides, the reaction and photocatalytic mechanism of the material preparation are discussed, and a possible catalytic mechanism has been proposed. Finally, we found that the excellent photocatalytic performance of our catalyst is due to the Z-scheme heterojunction and the associated advantages of respective components.