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 TiO ₂ 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.