Role of R in Bi₂RNbO₇ (R = Y, Rare Earth):  Effect on Band Structure and Photocatalytic Properties

We prepared a new series of rare earth photocatalysts, Bi 2 RNbO 7 (R = Y, rare earth), and found that the variation of R ion radius r R 3+ in Bi 2 RNbO 7 led to a change in the band structure and the activity of photocatalytic decomposition of water. The band gap E g increases with increasing r R 3+, while the photocatalytic activity A R 3+ decreases with increasing r R 3+ . The analysis of the E ( r R 3+ ) dependency showed that the position of the 4f band of the R ion in Bi 2 RNbO 7 determines the band gap E g, resulting in the difference in photocatalytic activity.