Photocatalysts fabricated by depositing plasmonic Ag nanoparticles on carbon quantum dots/graphitic carbon nitride for broad spectrum photocatalytic hydrogen generation

[Display omitted] •The combination of plasmonic Ag NPs with upconverted PL property from CQDs assists g-C3N4 to improve photocatalytic H2 evolution activity.•The Ag/CQDs/g-C3N4 nanocomposites can utilize broad spectrum to initiate reactions.•The synergistic effect of Ag, CQDs and g-C3N4 contributes to dramatical photoelectrons separation and photocatalytic capability. To make the best and highest use of broad spectrum solar energy remains a tremendous challenge and the main target in the photocatalytic area. A novel promising photocatalyst supported on surface plasmon resonance of Ag nanoparticles (NPs) and upconversion photoluminescence property from carbon quantum dots (CQDs) is reported to improve broad spectrum absorption and photoinduced charge transfer of graphitic carbon nitride (g-C3N4) in the photo-driven H2 production for the first time. Here the new-styled nanocomposites not only have more prominent UV–vis photocatalytic ability, also can harness near-infrared light to trigger hydrogen evolution in aqueous solution. Meanwhile, Ag NPs and CQDs serve as electron-reservoirs, which stimulate the separation of photo-generated electron-holes, enhancing quantum efficiency of g-C3N4. Remarkably, the most notable photocatalytic hydrogen generation as high as 626.93μmolg−1h−1 under visible light, which is about 6.7 and 2.8 times higher than pure g-C3N4 and the best CQDs/g-C3N4 composite respectively, was achieved upon 6mL CQDs/g-C3N4 (6CCN) loaded with 3wt% Ag. Moreover, a facile method is designed to prepare Ag/CQDs/g-C3N4 photocatalysts, and their chemical composition, morphologies, optical properties and stability were characterized methodically.