Fig. 4. Time course of water splitting activity of 5 × 5 cm² TiO₂/CoOOH/RhCrO_x/SrTiO₃:Al sheet in panel reactor. Reaction conditions: photocatalyst, 20 mg; reaction solution, 1 mm deep distilled water; reaction temperature, 291 K; light source, AM 1.5G solar simulator. Asterisk symbols (*) indicate interruption of the illumination for two days.