A novel photodeposition method in the presence of nitrate ions for loading of an iridium oxide cocatalyst for water splitting

IrO2 cocatalysts for water splitting were photodeposited from aqueous solution of (NH4)(2)[IrCl6] or Na-3[IrCl6] in the presence of nitrate ions on La-doped NaTaO3 (denoted as NaTaO3:La) photocatalysts, while metallic iridium particles were deposited in the absence of nitrate ions. The IrO2-loaded NaTaO3:La showed the activity for water splitting 2.5 times higher than the nonloaded NaTaO3:La. In contrast, the steady activity was not obtained for the metallic iridium-loaded photocatalyst, because the back reaction quickly proceeded.