  In this study, a complete study of the effect of hydrothermal reaction
temperatures on the synthesis and physical properties of V2O5 using the green
facile mild hydrothermal method has been performed with six different
temperatures 100 {\deg}C to 200 {\deg}C, in the step of 20 {\deg}C. . The XRD
pattern confirm the stable orthorhombic crystal structure of the synthesized
samples at all reaction temperatures. The SEM and TEM images demonstrate the
particle-like morphology, and these characterizations affirmed that the
particles size became larger with the increase of reaction temperatures. The
FTIR analysis is employed to study the functional groups, and the obtained
results are consistent with the XRD analysis. The bandgap has been estimated at
various reaction temperatures using UV-vis diffuse reflectance spectra (UV-DRS)
and was found to be varied 2.09 eV to 2.15 eV that are suitable range to absorb
a significant amount of visible light. The photocatalysis of methylene blue
(MB) with synthesized samples has been accomplished to investigate
photocatalytic efficiency. The pure V2O5 synthesized at lower reaction
temperature (100 {\deg}C) possess a lower bandgap and, accordingly, higher
photocatalytic efficiency.
