Abstract:
Three semiconductor metal vanadates FeVO4, BiVO4, and LaVO4 were synthesized. To improve the thermal catalytic and photocatalytic activity of highly efficient metal vanadate FeVO4, nanocomposites of
FeVO4 and graphitic C3N4 were prepared. Nanocomposites were prepared via thermal annealing method
by varying the composition of FeVO4 and g-C3N4. Catalysts were characterized by a series of complementary combination of powder X-ray diffraction, thermogravimetric analysis, N2 adsorption-desorption,
scanning/transmission electron microscopy, energy dispersive X-ray analysis, Fourier transform infrared
spectroscopy, diffuse reflectance ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy,
photoluminescence, and photoelectrochemical techniques. Catalysts were investigated in the liquid
phase oxidation of benzene, phenol, hydroquinone, naphthalene, anthracene, toluene, ethyl benzene,
di-phenyl methane, and p-xylene under conventional thermal condition and visible light irradiation condition. Kinetic and thermodynamic parameters (such as k, Ea, H, G, and S) were calculated for the
benzene hydroxylation by varying the reaction parameters under thermal catalytic condition. In order
to confirm the active species responsible for the thermal catalytic and photocatalytic processes, UV–vis,
fluorescence, cyclic voltammetry, and radical scavenging experiments were carried out with the help
of suitable probe molecules. Based on the results obtained, reaction mechanism was proposed, and the
structure-activity relationship was established. The catalyst was magnetically separated and recycled
with negligible loss in the activity which is important for the sustainable heterogeneous catalysis. The
developed catalytic process has the potential for the sustainable synthesis of a wide range of industrially important fine chemicals. Such a unique and detailed investigation of comparative study between
thermal catalysis and photocatalysis using FeVO4/g-C3N4 nanocomposite will be highly useful to design
optimum catalyst for an appointed catalytic reaction.
