APSUSC 330-2015-10

Structural rearrangement of mesostructured silica nanoparticlesincorporated with ZnO catalyst and its photoactivity: Effect of alkalineaqueous electrolyte concentration

ZnO-incorporated mesostructured silica nanoparticles (MSN) catalysts (ZM) were prepared by the intro-duction of Zn ions into the framework of MSN via a simple electrochemical system in the presence ofvarious concentrations of NH4OH aqueous solution. The physicochemical properties of the catalysts werestudied by XRD,29Si MAS NMR, nitrogen adsorption–desorption, FE-SEM, TEM, FTIR, and photolumine-scence spectroscopy. Characterization results demonstrated that the alkaline aqueous electrolyte simplygenerated abundant silanol groups on the surface of the catalysts as a consequence of desilication toform the hierarchical-like structure of the MSN. Subsequent restructuring of the silica network by thecreation of oxygen vacancies and formation of Si–O–Zn during the electrolysis, as well as formation ofnew Si–O–Si bonds during calcination seemed to be the main factors that enhanced the catalytic perfor-mance of photodecolorization of methyl orange. A ZM prepared in the presence of 1.0 M NH4OH (ZM-1.0)was determined to be the most effective catalyst. The catalyst displays a higher first-order kinetics rateof 3.87 × 10−1h−1than unsupported ZnO (1.13 × 10−1h−1) that prepared under the same conditions inthe absence of MSN. The experiment on effect of scavengers showed that hydroxyl radicals generatedfrom the three main sources; reduced O2at the conduction band, decomposed water at the valence bandand irradiated H2O2in the solution, are key factors that influenced the reaction. It is also noted that therecycled ZM-1.0 catalyst maintained its activity up to five runs without serious catalyst deactivation.