Stability of La dopants in NaTaO₃ photocatalysts

Doping NaTaO_³ with La typically results in increased photocatalytic activity. The photocatalytic activity of La-doped NaTaO₃ should therefore be sensitive to the photostability of the La species being doped. Unfortunately, the photostability of the La species in NaTaO₃ is not fully known. Herein, we perform an in-depth study on the photostability of the La species. Advanced characterization techniques, including X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS), are employed to clarify the chemical state and local structure of the La species in NaTaO₃. Our findings show that the examined La-doped NaTaO₃ can be effectively reused for six consecutive runs without a significant loss of its photocatalytic activity for the decomposition of recalcitrant organic compounds under UV light. The reusability of La-doped NaTaO₃ is proposed to be due to the photostability of the La species. The La species are photostable because their oxidation state is unaltered and their structure in the host NaTaO₃ is well preserved.