Study of the enhanced visible-light-sensitive photocatalytic activity of Cr2O3-loaded titanate nanosheets for Cr(VI) degradation and H2 generation

Visible-light-sensitive titanate nanosheets (TNSs) were synthesized with Cr2O3 successfully loaded and well dispersed on Cr(III)-TNSs by a one-step hydrothermal method for enhanced photocatalytic activity. As in our previous reports, the as-prepared samples clearly exhibited a porous flake-like structure with a large specific surface area (300-400 m(2) g(-1)). Accompanied with the hydrothermal growth of the TNSs, the loaded Cr2O3 not only influenced the layered structure of the TNSs, but also brought about a remarkable enhancement of the visible-light response and the separation of photogenerated carriers. The XPS fitting results indicated that the Cr ions mainly existed in the trivalent form and caused a change in the binding states towards Ti and O. Based on the evaluation of the photocatalytic activity, it was found that the Cr(III)TNSs obtained a significant improvement for RhB and K2Cr2O7 (Cr(VI)) degradation under visible-light irradiation, which was attributed to retarding the charge recombination and the effective electron transfer from Cr2O3 to TNSs. The better photocatalytic activity was obtained with an optimal content (0.5 at%) of Cr3+, and the degradation rate (K-app) was 2.9-fold and 4.1-fold, respectively, as compared to TNSs. The samples were also evaluated in photocatalytic H-2 generation with the photodeposition of Pt nanoparticles as cocatalysts. The results showed that the visible-light H-2 production rate of Pt-0.25/Cr(III)-TNSs (0.25 wt% of Pt) was observably enhanced under the efficient sacrificial agent/water system, giving a relatively high H-2 generation rate of 473 mu mol h(-1) g-1 at 0.5 at% of Cr3+ content. The cyclic tests demonstrated the good stability and recycling performance of the samples. Alternative mechanisms for the visible-light-sensitive photocatalytic activity were also proposed.