Preparation and characterization of Cs1·48Sb0·78PMo11VO40. Application to the photo catalytic oxidation of orange II under solar light

Abstract

Cs1·48Sb0·78PMo11VO40 (CsSbPMoV) was prepared and characterized by many physico-chemical techniques. The spectroscopies 31P MAS-NMR, FT-IR) and X-ray diffraction showed that the salt is pure, of Keggin-type crystallizing in a cubic structure.The UV–Vis spectrum revealed the presence of molybdenum and antimony with mixed valence states, Mo(VI)/Mo(V) and Sb(V)/Sb(III). The optical properties showed two transitions: directly (1.20eV) and indirectly (1.38eV) allowed. The intensity-potential (J- E), plotted in Na2SO4 (0.1 ​M), exhibited a sluggish electrochemical system. The capacitance−2– potential (C−2 - E) curve showed n-type behavior with a flat band potential (Efb) of 0.10 ​V and a conduction band positioned at 4.65 ​eV, below vacuum (−0.1 VSCE), composed mostly of (Mo, Sb) 5s wave functions, negative of the •OH/H2O level. Therefore, CsSbPMoV was successfully tested for theoxidation of Orange II (OII), a hazardous dye, by •OH and O2•radicals under solar light. The discoloration obeys a first order kinetic model with an abatement yield of 68% and a photo catalytic half-life (t1/2) of 60 ​min.