The atomic-scale structure of LaCrO₃-NaTaO₃ solid solution photocatalysts with enhanced electron population

Visible light sensitization of sodium tantalate (NaTaO3), a highly UV-active material, is critical for realizing its practical application in photocatalytic water splitting under solar light. Double doping of a half-filled transition metal together with another metal for cationic charge balance is a promising way of sensitizing NaTaO3 to visible light. One fundamental issue is that the atomic-scale structure of such doubly doped NaTaO3 is not yet fully understood. In this study, we doubly doped NaTaO3 with La3+ and Cr3+ through a solid-state route. The occupation preference of La3+ in a doubly doped system was particularly studied by the extended X-ray absorption fine structure technique. We revealed the substitution of La3+ for Na+, and Cr3+ for Ta5+, forming a LaCrO3-NaTaO3 solid solution. We then showed that doping NaTaO3 with La3+ and Cr3+ appreciably increased the population of electrons photoexcited by either visible light or UV light. Photoactivation of the doubly doped NaTaO3 with visible light produced a population of electrons comparable to that under UV light. The charge compensation scheme of double doping with La3+ and Cr3+ is shown here to be a good option for the sensitization of NaTaO3 to visible light.