Photocatalytic removal of MB and hydrogen evolution in water by (Sr0.6Bi0.305)2Bi2O7/TiO2 heterostructures under visible-light irradiation.

The pyrochlore-type (Sr 0.6 Bi 0.305) 2 Bi 2 O 7 (SBO) containing Bi3+ and Bi5+ mixed valent states was first investigated as a photocatalyst in our very recent work. To further improve the photocatalytic performance, SBO/TiO 2 heterostructured composites were successfully fabricated using a single-step hydrothermal method. The photocatalytic activity of as-prepared samples was evaluated by the degradation of methylene blue under visible light irradiation and photocatalytic hydrogen generation using water. SBO/TiO 2 composites exhibited remarkably enhanced photocatalytic activity and high stability. The enhancement of photocatalytic performance is attributed to the increase of light absorption and the separation of photogenerated carriers on the interface of SBO/TiO 2 heterostructured composites. • (Sr 0.6 Bi 0.305) 2 Bi 2 O 7 /TiO 2 composites exhibit excellent photocatalytic activity and high stability in photocatalytic removal of MB and hydrogen evolution. • The mechanism of MB photodegradation and photocatalytic generating hydrogen under visible light on (Sr 0.6 Bi 0.305) 2 Bi 2 O 7 /TiO 2 were explored. • The formation of heterojunction should be directly responsible for the enhancement in photocatalytic efficiency of composites. Accelerating the separation efficiency of photoexcited electron-hole pairs with the help of binary heterojunction structure is considered to be a promising approach for significantly enhancing the photocatalytic hydrogen production performance of TiO 2. Providing more (Sr 0.6 Bi 0.305) 2 Bi 2 O 7 (SBO) catalysts to function as active sites of TiO 2 , together with the ability to construct heterojunction structures, is highly desirable for photocatalytic hydrogen evolution and pollutant photodegradation. To achieve this goal, in this work, (Sr 0.6 Bi 0.305) 2 Bi 2 O 7 /P25 (SBO/P25) binary heterojunction catalyst is formed in situ on the TiO 2 surface by a simple one-step hydrothermal method. To evaluate the feasibility of SBO/P25 as a very efficient photocatalyst for degradation of MB and photocatalytic hydrogen evolution, a series of photocatalytic experimental studies were carried out. The experimental result indicated that the existence of heterojunction structure in the SBO/P25 nanocomposites improves the photocatalytic activity of P25. The photocatalytic performance of H 2 evolution from water splitting and MB degradation for an optimal SBO/P25 photocatalyst reached 3.18 mmol g–1 h−1 and 3.42 × 10−2 min−1, respectively, which were 7.40 and 5.26 times higher than those of pure P25, respectively. The significantly improved catalytic capability on SBO/P25 is mainly ascribed to the enhanced visible light absorption and charge transfer in comparison with P25. In addition, SBO/P25 composites have excellent stability and recyclability, showing great potential for application in wastewater treatment and photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]