Facile synthesis of nanostructured monoclinic bismuth vanadate by a co-precipitation method: Structural, optical and photocatalytic properties

We report the synthesis of bismuth vanadate (BiVO₄) nanostructure by atoxic-free, inexpensive co-precipitation method. The BiVO₄ nanostructures were derived from bismuth nitrate and ammonia metavanadate as starting precursors and sodium hydroxide (NaOH) were used as stabilizers for tuning the morphology (nanorod, nanospheriod and nanoparticulate). The influence of post-calcination treatment (450, 550 and 650 °C) on structural, optical and photocatalytic properties of BiVO₄ was studied. The post-calcination treatment strongly induces the crystallization process and produce monoclinic BiVO₄ structure with predominant (112) crystallite phases. The absorbance of BiVO₄ shows broad coverage of visible light wavelength region up to 550 nm, which is appreciable for solar light driven photocatalysis. Among the different calcinated samples, anisotropy rod-shape BiVO₄ (calcinated at 450 °C) shows high optical absorbance than other treated (550 and 650 °C) samples. The monotonic shift in characteristic Raman vibration mode at 824 cm^-1 with increasing calcination temperature indicates that the V-O bond length is affected by Bi³⁺ diffusivity. The PL spectra of these samples explore the intrinsic defects present in BiVO4, and found to be high in high temperature calcinated samples. The photocatalytic property of resultant BiVO₄ samples was evaluated in oxygen generation with Ag⁺ donors. As a result of reduced defects and high optical absorbance, the BiVO₄ calcinated at 450 °C showed high photocatalytic oxygen yield (1.02 mmol) compared with high temperature calcinated samples (0.48 mmol).The appreciable quantity of solar fuel O₂ generation from the low-cost co-precipitation method can be widely implemented in other visible light metal oxide nanostructures.