TiO2 nanosheets with exposed {001} facets co-modified by AgxAu1−x NPs and 3D ZnIn2S4 microsphere for enhanced visible light absorption and photocatalytic H2 production

A novel Ag_xAu_1−x/ZnIn₂S₄/TiO₂ photocatalyst with high photoactivity under visible light illumination is designed in this work, in which ZnIn₂S₄ displays a 3D flower-like microsphere structure, while TiO₂ nanosheets with highly active {001} facets (TiO₂ NS) are tightly embedded in the interspaces of ZnIn₂S₄ microspheres, and Ag_xAu_1-x nanoparticles (NPs) are loaded on its surface, respectively. The exquisite design of Ag_xAu_1−x/ZnIn₂S₄/TiO₂ makes it possess remarkable superiority in photocatalysis. Firstly, by the dual modification of ZnIn₂S₄ and Ag_xAu_1−x, the Ag_xAu_1−x/ZnIn₂S₄/TiO₂ displays a strong absorption in visible light region, and their absorption region can be modulated by changing the ratio of Ag and Au in Ag_xAu_1-x nanoparticles due to the plasmon coupling effect of Ag and Au. Secondly, the high separation and transfer efficiency of photogenerated carriers is achieved in Ag_xAu_1-x/ZnIn₂S₄/TiO₂ by utilizing TiO₂ as the electron transfer intermediary of ZnIn₂S₄ and Ag_xAu_1−x. All of these make Ag_xAu_1−x/ZnIn₂S₄/TiO₂ exhibit an evident enhancement in the photocatalytic activity of H₂ production. Significantly, the hydrogen production amount and rate of Ag_0.2Au_0.8/ZnIn₂S₄/TiO₂ with 60 wt% ZIS after 10 h are 9862 μmol/g and 986.2 μmol/g/h, which is around 2098 times of pristine TiO₂. The apparent quantum yield of Ag_0.2Au_0.8/ZnIn₂S₄/TiO₂ after 10 h is about 1.47%. Moreover, the cycling test reveals that Ag_xAu_1−x/ZnIn₂S₄/TiO₂ shows the high stability in photocatalytic water spitting. Based on the characterization and photocatalytic results, the proposed photocatalytic mechanism is proposed.