Novel GdTaO4 phase for efficient photocatalytic degradation of organic dye under visible light irradiation: An X-ray spectroscopic investigation

Abstract

The novel GdTaO₄ phase exhibits good photocatalytic activity under visible light irradiation and holds great promise for the removal of organic dyes from industrial wastes. The GdTaO₄ samples were synthesized using the hydrothermal and calcination process with different weight ratios of gadolinium nitrate hydrate (G) and tantalum pentachloride (T), and their structural studies confirmed the formation of the GdTaO₄ (GT) phase. Among the samples, GT-4 (with a weight ratio of 4:1) exhibited the highest photocatalytic activity for the degradation of Methyl Orange (MO) dye under visible light irradiation. To enhance the photocatalytic performance, H₂O₂ was used as a green additive, and the photocatalytic abilities were examined by varying dye types and concentrations. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) revealed the local atomic and electronic structures around Ta and Gd and highlighted the contribution of Gd³⁺ to the GT system, which is a crucial factor in supporting the enhanced photocatalytic performance. Moreover, in-situ XAS at Gd M₅-edge and O K-edge were examined under illumination/dark conditions to explore the electronic structures of photo-excited electron transition in the photocatalytic process. The analytical results provided strong evidence correlating the electronic structure and photocatalytic property of the GT. This study demonstrates that GdTaO₄ exhibits good photocatalytic activity under visible light irradiation, making it a promising new Ta-based photocatalyst for the effective removal of organic dyes from industrial wastes.

Keywords: GdTaO(4); Methyl orange (MO); Photocatalyst; Photocatalytic degradation; X-ray absorption spectroscopy (XAS); X-ray photoelectron spectroscopy (XPS).