Effective mineralization of organic dye under visible-light irradiation over electronic-structure-modulated Sn(Nb 1−x Ta x ) 2 O 6 solid solutions

A series of Sn(Nb 1− x Ta x ) 2 O 6 solid solutions were successfully synthesized as novel visible-light-active photocatalysts. The characterizations of powder X-ray diffraction and UV–vis absorption spectrum indicate that these solid solutions possess continuous changes in the crystallography features and optical band gaps, and are therefore a group of continuous solid solutions. Their photocatalytic properties were evaluated via methylene blue (MB) photodegradation. The Sn(Nb 0.8 Ta 0.2 ) 2 O 6 sample showed the best photocatalytic performance, full mineralization ability, and an excellent stability. After 120 min of irradiation, the degradation and mineralization percentages of MB over Sn(Nb 0.8 Ta 0.2 ) 2 O 6 reached 99.5% and 98.9%, respectively; in addition, the degradation ratio remained at 97% after five-cyclic test. The further study on the active species and the theoretical calculation based on density functional theory helped to clarify the mechanism of the photodegradation reaction. On this basis, we propose the strategies to design high-performance photocatalysts employed in hole-dominated and electron-dominated photocatalytic applications, respectively.