Modification of TiO2 by Bimetallic Au-Cu Nanoparticles for Wastewater Treatment

Au, Cu and bimetallic Au–Cu nanoparticles were synthesized on the surface of commercial TiO2 compounds (P25) by reduction of the metal precursors with tetrakis(hydroxymethyl) phosphonium chloride (THPC) (0.5% in weight). The alloyed structure of Au–Cu NPs was confirmed by HAADF-STEM, EDS, HRTEM and XPS techniques. The photocatalytic properties of the modified TiO2 have been studied for phenol photodegradation in aqueous suspensions under UV-visible irradiation. The modification by the metal nanoparticles induces an increase in the photocatalytic activity. The highest photocatalytic activity is obtained with Au–Cu/TiO2 (Au–Cu 1 : 3). Their electronic properties have been studied by time resolved microwave conductivity (TRMC) measurements to follow the charge-carrier dynamics. TRMC measurements show that the TiO2 modification with Au, Cu and Au–Cu nanoparticles plays a role in charge-carrier separations increasing the activity under UV-light. Indeed, the metal nanoparticles act as a sink for electrons, decreasing the charge carrier recombination. The TRMC measurements also show that the bimetallic Au–Cu nanoparticles are more efficient in electron scavenging than the monometallic Au and Cu ones.