Facile construction of a dual-Z-scheme TiO2/CaTi4O9/CaTiO3 heterojunction photocatalyst with superior photocatalytic performance for hydrogen production and Cr(VI) reduction

Ti-based semiconductors the eco-friendly materials. Here, using n-tetrabutyl titanate and calcium acetate as raw materials, a dual- Z -scheme TiO 2 /CaTi 4 O 9 /CaTiO 3 heterojunction was facilely constructed via the solvothermal combination with calcination route. The obtained samples were intensively characterized by some physicochemical methods such as TG, XRD, FT-IR, SEM , TEM, XPS, UV–Vis DRS, PL , N 2 physisorption-desorption, and electrochemical tests. The optimum TiO 2 /CaTi 4 O 9 /CaTiO 3 photocatalyst fabricated at a solvothermal temperature of 160 °C and calcination temperature of 700 °C shows high efficiency for H 2 production, which was 11, 5, and 1.6 times higher than that of rutile-phase TiO 2 , CaTiO 3 and commercial P25(TiO 2 ), respectively. The Cr(VI) reduction rate over TiO 2 /CaTi 4 O 9 /CaTiO 3 was 3.3, 5.2, and 3.1 times higher than those of rutile-phase TiO 2 , CaTiO 3, and commercial P25, respectively. The superior photocatalytic performance is attributed to the strong redox ability of carriers excited by wide band gap semiconductors and the unique dual- Z -scheme which largely promotes carrier separation.