A hollow core-shell TiO2/NiCo2S4 Z-Scheme heterojunction photocatalyst for efficient hydrogen evolution
Constructing heterojunctions have received significant attention in photocatalysis because of their efficient separation of photogenerated carriers and improving light utilization efficiency. Bimetallic sulfides (e.g. NiCo 2 S 4 ) are applied in electrocatalysis and supercapacitors that can be coupled with TiO 2 to form a heterojunction . Owing to the staggered energy band arrangement between TiO 2 and NiCo 2 S 4 , the establishing of a Z-scheme heterojunction between them is expected to enhance the carrier separation efficiency and reduce the sulfide photo-corrosion. However, the application of NiCo 2 S 4 in photocatalysis and studies on the mechanism of the TiO 2 /NiCo 2 S 4 Z-scheme heterojunction have seldom been reported. In this work, we obtained a hollow core-shell TiO 2 /NiCo 2 S 4 Z-scheme photocatalyst through a solvothermal method for photocatalytic hydrogen evolution (PHE). The PHE rate of the optimized TiO 2 /NiCo 2 S 4 -0.3 is 8.55 mmol g − 1 h − 1 , approximately 34 times higher than pure TiO 2 , 94 times higher than pure NiCo 2 S 4 . The remarkable photocatalytic activity can be ascribed to the hollow structure and the in-situ constructed Z-scheme heterojunction. The photogenerated charge transfer mechanism is revealed by hydroxyl radical trapping experiments and electron paramagnetic resonance (EPR) characterization. The in-situ construction of the Z-scheme heterojunction not only enhances the efficiency of separating the photogenerated carriers but also reduces the photo-corrosion of NiCo 2 S 4 . This study proposes an effective strategy for the design of TiO 2 -based Z-scheme heterojunctions and the application of NiCo 2 S 4 in photocatalysis .
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