Fabrication and a detailed study of an La3+-doped BiVO4 nanophotocatalyst for environmental remediation

Abstract

The treatment of a water pollutant, methylene blue (MB) dye, by an advanced oxidation process via the fabrication of a novel photocatalyst, La ion-doped BiVO₄ (La:BiVO₄), is presented in this work. La:BiVO₄ photocatalysts containing 1, 3, 5, 10, and 20 mol% La content were prepared with a nanosheet microstructure by the hydrothermal method. These photocatalysts were characterized using X-ray diffraction, UV-vis, Raman, FTIR, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The La:BiVO₄ photocatalyst exhibited a monoclinic scheelite structure with crystallite sizes below 30 nm. The photocatalytic activity of the photocatalysts was evaluated by degrading the methylene blue (MB) dye under visible light irradiation. The photocatalyst with 1 mol% La showed 93.4% MB degradation within 300 min of irradiation, following first-order reaction kinetics with a rate constant of 0.02076 h⁻¹. The enhanced activity was attributed to the reduced charge-transfer resistance due to the optimum band gap. Scavenging experiments showed that the photogenerated electrons are the dominant reactive species in degrading the MB dye over other radicals. The La:BiVO₄ photocatalyst demonstrated satisfactory performance under neutral pH conditions and exhibited excellent recyclability and structural stability over multiple uses of photocatalytic cycles. Thus, the La:BiVO₄ nanosheet photocatalyst possesses efficient capability to degrade the methylene blue dye, and hence, it is a novel environmental remediation material.