Paper Title
Calcination Temperature on the Photocatalytic Properties of Facile Synthesized Monoclinic Bismuth Vanadate Nanopowders

Abstract
We have synthesized bismuth vanadate (BiVO4) nanostructure by toxic-free, inexpensive co-precipitation method. The BiVO4 nanostructures were derived from bismuth nitrate and ammonia metavanadate as starting precursors and sodium hydroxide (NaOH) was used as stabilizer 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 were studied. The post-calcination treatment strongly induce the crystallization process and produce monoclinic BiVO4 structure with predominant (112) crystallite phases. The absorbance of BiVO4¬¬ show 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 °C and 650 °C) samples. The monotonic shift in characteristic Raman vibration mode at 824 cm-1 with increasing calcination temperature indicates that, 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 m.mol) compared with high temperature calcinated samples (0.48 m.mol).The appreciable quantity of solar fuel O2 generation from low-cost co-precipitation method can be widely implemented in other visible light metal oxide nanostructures. Keywords: Co-precipitation, Bismuth vanadate, Raman, Photoluminescence, oxygen generation