Structural, electronic and optical features of molybdenum-doped bismuth vanadium oxide

Abstract

Molybdenum (Mo)-doped bismuth vanadium oxide (BiVO4) powders were prepared by a sol–gel method. X-ray diffraction (XRD) patterns and micro-Raman vibrational bands confirm the monoclinic scheelite phase. Molybdenum doping of BiVO4 matrix was confirmed from XRD by higher angle 2θ shift of the characteristic peak (−121) and from Raman showing lower frequency shift of dominant band from 831 to 822cm−1 which corresponds to V–O symmetric stretching mode. EPR investigations confirmed the substitution of Mo in the crystalline sites of monoclinic BiVO4. SEM analysis showed spherical shaped particles around 100–200nm with weak agglomerated particles. Homogeneous presence of molybdenum in BiVO4 matrix was confirmed from STEM analysis. Diffuse reflectance spectra showed higher absorption in the range of 550–850nm and optical band gap energies were calculated by using the Kubelka–Munk formula, i.e, 2.46eV for 2wt% Mo–BiVO4 and 2.48eV for undoped BiVO4. This confirms that, Mo–BiVO4 particles have almost the same energy band gap but induce higher absorption in the visible light region as compared to undoped material.