Efficient water splitting over Na1−xKxTaO3 photocatalysts with cubic perovskite structure

This study improved the photocatalytic activity of NaTaO3 by replacing some Na ions in the 12-coordinate sites with larger K ions. Na1−xKxTaO3 photocatalysts of x = 0–0.2 were synthesized by the sol–gel method. K-doping at x = 0.05 resulted in rectifying the distorted perovskite NaTaO3 to a pseudo-cubic phase as well as significantly promoting the photocatalytic activity. The 180° bond angle of Ta–O–Ta in the pseudo-cubic phase may facilitate the separation of photogenerated charges for effective water splitting. Photoluminescence spectroscopic analysis confirmed that the flattened Ta–O–Ta linkage with K-doping suppresses the recombination of photogenerated charges. Further K-doping (with x > 0.05) leads to impurity formation, which bends the Ta–O–Ta linkage and creates defect states, lowering the photocatalytic activity of the K-doped NaTaO3. This study demonstrates that an appropriate ion replacement to tune the crystal structure can significantly promote electron transport in photocatalysts and thus their activity.