TiO2as an interfacial-charge-transfer-bridge to construct eosin Y-mediated direct Z-scheme electron transfer over a Co9S8quantum dot/TiO2photocatalyst

The direct Z-scheme heterojunction is an ideal system for photocatalytic H(2)production, which can efficiently separate photogenerated charges and maintain stronger redox ability. Herein, for the first time, a novel direct Z-scheme Co(9)S(8)quantum dots/TiO2(Co(9)S(8)QDs/TiO2) photocatalytic system was constructed in the presence of eosin Y (EY) with TiO(2)as an interfacial-charge-transfer-bridge. The amorphous Co(9)S(8)QDs were successfully anchored on the surface of TiO(2)viaanin situhydrothermal method. The spatial behavior of photocarriers was effectually regulated based on the bandgap-matching theory, which greatly decreased the recombination of the electrons and holes of Co9S8. Most importantly, TiO(2)serving as an interfacial-charge-transfer-bridge can promote the electron transfer of excited-state EY to the valence band of Co(9)S(8)QDs to scavenge its photogenerated holes, causing Z-scheme charge transfer in the intimate interface between Co(9)S(8)QDs and TiO2. As a result, a maximum H(2)production rate of 2813.9 mu mol h(-1)g(-1)was achieved over the 20%Co(9)S(8)QDs/TiO(2)heterojunction, which is 3.3 and 197.5 times greater than that of Co(9)S(8)QDs and TiO2, respectively. A high AQE of 37.4% was obtained at 470 nm for 20%Co(9)S(8)QDs/TiO2. The Z-scheme charge transfer mechanism was confirmed by comparative experiment analysis, time-resolved fluorescence (TRPL) decay, andin situPt photodeposition. The present work provides a novel approach to constructing Z-scheme photocatalytic systems for efficient artificial solar energy conversion.