Photocatalytic activity of LaTaON₂ powders prepared using an oxide precursor derived from a hydrothermal reaction

Abstract

Plate-like LaTaON₂ was prepared by the nitridation of plate-like LaTaO₄ precursor synthesized by hydrothermal method to improve the photocatalytic activity for H₂ evolution from an aqueous methanol solution under visible light irradiation. LaTaON₂ samples derived from hydrothermal method consisted of only slightly aggregated particles 5–10 μm in size. In contrast, LaTaON₂ samples derived from solid-state reaction method consisted of irregular-shaped and aggregated primary particles 0.5–1.5 μm in size. For photocatalytic H₂ evolution using Pt as a co-catalyst, plate-like LaTaON₂ exhibited higher photocatalytic activity than irregular-shaped LaTaON₂. In addition, ultraviolet-visible diffuse reflectance spectra suggested that plate-like LaTaON₂ had a lower density of defects due to the presence of anion vacancies or reduced Ta⁵⁺ species than irregular-shaped LaTaON₂, as demonstrated by the reduced intensity of absorption at longer wavelengths (λ ＞ 660 nm). Therefore, using a LaTaO₄ precursor synthesized by hydrothermal method, we obtained LaTaON₂ with reducing the density of defects that act as recombination centers for photogenerated carriers.