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

Abstract

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.