Résumé
One of the important challenges encountered in photocatalysis applications is to fabricate high performance photocatalysts with an easy and low-cost fabrication method and sustaining a slow hole-electron recombination rate. The latter can be achieved by promoting the synergetic effect between noble metals and metal oxides such as titanium oxide (TiO 2 ) . In this work, gold nanostars/TiO 2 (GNS/TiO 2 ) nanocomposites were prepared using the impregnation method. A study of the dependence of the size on the synergetic effect of GNS/TiO 2 nanocomposites was investigated using TiO 2 nanoparticles with an average size of 5 nm and 20 nm, respectively. The structural, morphological, elemental and optical properties of GNS/TiO 2 nanocomposites were studied by X-ray diffraction (XRD), High-resolution transmission electron microcopy (HRTEM), Energy dispersion X-ray (EDX), selected area electron diffraction (SAED), Raman spectroscopy, adsorption/desorption isotherm, and UV-Vis optical spectroscopy techniques. The photocurrent study was performed with different films of GNS/TiO 2 nanocomposites indicating the importance of the size to enhance photocurrents with the presence of GNS.
The photocatalytic activity of the prepared nanocomposites was studied toward the photodegradation of the Naphthol Green B complex dye. 5 nm and 20 nm pure anatase TiO 2 exhibited a very fast degradation of the dye during 19 and 70 minutes with kinetics reaction rate of 0.078 and 0.03 min -1 respectively. By adding GNS, 5 nm and 20 nm GNS/TiO 2 showed shorter photodegradation time of 10 and 15 minutes with kinetics reaction rate of 0.241 and 0.155 min -1 respectively. The latter confirms the strong synergetic effect between GNS and 5nm TiO 2 that may come from its smaller size compared to the 20 nm TiO 2 nanocomposite system. The first principal calculations were performed to study the stability and electronic structures of the Au/TiO 2 composite interface. The interfacial charge properties and the potential drop between the gold and TiO 2 were also studied. The adsorption energies of the Naphthol Green B on the Au/TiO 2 composite interface were also examined.