Composition-dependent structure evolution of FeVO4 nano-oxide and its visible-light photocatalytic activity for degradation of methylene blue

This work report on the synthesis of the iron orthovanadate oxide (FeVO4) catalysts with various vanadium (V) loading amounts of 10% (FeV-1); 20 wt% (FeV-2); 30 wt% (FeV-3) and 40 wt% (FeV-4). The structure evolution of FeVO4 was studied by using XRD, UV-vis, PL, FTIR, XPS, SEM, EDX, TEM, EIS, Raman and BET surface area techniques. XRD analysis showed that crystal structure and phase formation of FeVO4 to depend on V-metal loadings, and that the various Fe:V ratio showed peaks shifting, which were related to the transformation of Fe2O3 and V2O5 interface into FeVO4 phase with respect to increasing V-metal loadings. The XPS results showed the significant influence of the V-metal loadings on inducing various electronic, redox oxidation states of V3+/V4+/V5+ and Fe2+/Fe3+ and oxygen vacancy defects structure properties of FeVO(4 )catalysts. The physical structure changes confirmed by XRD, XPS and FTIR manifested the tailoring of the optical properties as evidenced by PL and UV-vis with FeV-3 catalyst showing the desirable optics properties. This were determined to give the properties for the efficient photodegradation activity of methylene blue model organic dye of wastewater with its near complete removal with 30 min reaction time. The enhanced productivity photodegradation performance of the hetero-mixed FeVO4 catalysts is ascribed to their enriched visible-light harvesting range and efficient suppression of electrons/holes (e(-)/h(+)) recombination manifested by the effect of Fe:V composition ratio. Moreover, the presence of small quantity of Fe2O3 in predominant FeVO4 could allow efficient e(-)/h(+) separation and transfer by creation of Fe2O3/FeVO4 heterojunction interface. The FeVO4 catalyst showed excellent recyclability and its stable photoactivity under aqueous degradation conditions.