Hydrothermal synthesis, characterization, and photocatalytic degradation of Rhodamine B dye of triazole modified molybdenum oxide

Molybenuym oxide triazole [MoO3(Htrz)(0.5)]; Htrz = 1,2,4 Triazole] (Mo-Htz) was synthesized for the first time by hydrothermal route at 180 degrees C by using heteropolyacid as molybdenum source. The as-prepared material was characterized by X-Ray Diffraction (XRD), UV visible diffuse reflectance, thermal analysis, FT-IR and Raman spectroscopies. The XRD pattern shows narrow peaks and Mo-Htz crystallizes in an orthorhombic symmetry (SG: Pbcm): a/angstrom: 3.933(1), b/angstrom: 13.856(1), c/angstrom: 13.367(4). The crystal structure consists of Mo octahedron bonded to Htz molecules forming a layered structure with double [Mo2O6 (Htrz)](n) chains connected via a corner-sharing connection. Raman spectroscopy shows characteristic peaks of Mo=O, O-Mo-O and O=Mo=O for MoO3. The FT-IR spectrum corroborates the structure of the compound and confirms the existence of Htz and Mo-O bonds. SEM image displays a thin lamellar structure and EDS analysis quantify the elemental composition of a material. The band gap energies change from 2.93 eV (bare MoO3) to 2.95 eV (Mo-Htz) due to synergy effect. The current-potential (J-E) curve plotted in Na2SO4 electrolyte showed a medium hysteresis with electrochemical stability. The n-type semi conductivity, was indicated by negative slope of the capacitance(-2) - potential (C-2 - E) graph and supported by the electrochemical impedance spectroscopy (EIS) under visible light illumination. The conduction band (4.19 eV/-0.56 V-SCE), is formed by the Mo6+: 3d orbital, where excited electrons reduce oxygen into O-2(center dot-) radicals, involved in the Rhodamine B (Rh B) oxidation. An abatement of 60 % was reached by coupling "adsorption/photocatalysis" (5 h) under visible light. The degradation of Rh B follows a first order kinetic with a half-life of similar to 3 h.