Investigation onto the performance and mechanism of visible light photodegradation of methyl orange catalyzed by M/CeO2 (M=Pt, Ag, Au)

In this paper, M/CeO2 (M=Pt, Ag, Au) photocatalysts were prepared and used for visible light degradation of methyl orange (MO) with H2O2 as a sacrificial reagent. Utilizing X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), N2 physical adsorption (BET), X-ray photoelectron spectroscopy (XPS), photocurrent characterization and electrochemical impedance spectroscopy, etc., the structure, morphology, chemical state, and optical properties of the catalyst were investigated. The effects of the amount of catalyst, the initial concentration of methyl orange, the pH value of the solution and the number of reuses on the photocatalytic degradation efficiency of MO were studied. The results showed that under optimized reaction condition of 15 mg 2Pt/CeO2 catalyst, the initial concentration of MO was 20 mg/L, pH=5, the reaction time was 195 min and the amount of H2O2 was 0.2 mL, the degradation percentage of MO reached 75.8%. The main active species of photodegradation are hydroxyl radicals and superoxide radicals, which was determined by free radical capture experiments and combined electron spin resonance (ESR). The photocatalytic mechanism based on work function difference and electron transfer was also discussed in detail.