Photodynamics of NaTaO₃ Catalysts for Efficient Water Splitting

Electrons photoexcited in catalysts based on NaTaO₃ were observed by time-resolved infrared (IR) absorption spectroscopy. The electrons excited by 266-nm pump pulse exhibited a monotonic absorption of mid-IR light. The recombination kinetics of the excited electrons with holes was monitored in a vacuum as a function of time delay ranging from 100 ns to 1 s. When the Na content and La dopant were optimized to achieve high activity in the steady-state reaction of water splitting, the recombinative decay was hindered to increase the amount of electrons. The electrons were transferred to NiO ultrafine particles, loaded as a cocatalyst, within 1 μs following the pulse excitation. Exposing the catalysts to water vapor affected the electron decay and efficient electron transfer to water via the cocatalyst was evidenced.