Au nanoparticles assembled on palygorskite: Enhanced catalytic property and Au-Au2O3 coexistence

Au nanoparticles were assembled on palygorskite (PAL) to form Au/PAL nanocomposites via a deposition-precipitation method. Samples were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and gas chromatography (GC). Results indicated that Au nanoparticles, with a particle size of 2-7 nm, were uniformly immobilized on the surface of PAL with the coexistence of Au and Au2O3. Ortho-dichlorobenzene (o-DCB) was first fixed on Au2O3 then completely oxidized to CO2, H2O, HCl by metallic Au. The reaction rate of o-DCB was approximately second order with calculated activation energy of -3.4 kJ/mol, while the reaction order of O-2 was zero order under sufficient oxygen. The catalytic activity could reach 99% at a Au/(Au + Au2O3) molar ratio of 0.83, three times of that without PAL support. Mechanism for enhanced catalytic activity under Au-Au2O3 coexistence system was discussed. (C) 2013 Elsevier B.V. All rights reserved.