Impact of europium doping on bismuth vanadate nanopowder's morphological, optical, and photocatalytic characteristics

Introduction: Organic dyes in wastewater are recognized as critical environmental contaminants, dictating the development of effective remediation strategies. Semiconductor photocatalysts are a promising class of materials for pollutant degradation. Among these, BiVO₄ has emerged as one of the most widely studied materials. However, the restricted separation of photogenerated electron-hole pairs significantly limits their application. Notably, doping Bi-based photocatalysts with rare-earth metals efficiently increases their photocatalytic activity. This work demonstrates a viable, microwave-assisted (MW) route for developing Eu³⁺-doped BiVO₄ nanocatalysts for practical wastewater remediation.

Methods: Nanostructured BiVO₄ and Bi_0.88Eu_0.12VO₄ samples were prepared using a MW method. After 10 minutes of radiation, a yellow powder is produced by MW heating at 170 °C. Photocatalytic activities of the as-prepared samples were determined through the decolorization of Rhodamine B (RhB) under visible light irradiation. In a standard experiment, 50 mL of RhB solution with a 5 ppm concentration was mixed with 40 mg of the sample and subjected to 100 min of irradiation.

Results: The Eu³⁺-doped BiVO₄ has been analyzed using XRD to confirm the presence of a mixture of ms-BiVO₄ and tz-BiVO₄ phases. The crystallite size, calculated using the Debye-Scherrer formula, increases from 16 for BiVO₄ to 55 nm for the Bi_0.88Eu_0.12VO₄ sample. The TEM images show that both samples contain well-crystallized, irregular spheroidal nanoparticles. The FTIR analysis reveals characteristic peaks of undoped BiVO₄ and two additional peaks at 471 and 720 cm⁻¹, which are attributed to Eu-O stretching vibrations. Photocatalytic experiments revealed a decrease in absorbance intensities of RhB at 554 nm. In contrast to the undoped BiVO₄, with a removal efficiency of 81%, the Eu³⁺-doped BiVO₄ sample exhibited higher efficiencies of 97% for Bi_0.88Eu_0.12VO₄.

Conclusions: This integrated green synthesis strategy provides a novel pathway for tailoring the structural and optical properties of Eu-doped photocatalyst, resulting in significantly higher photocatalytic degradation of organic dye RhB under visible light.