Mono- and Dual-modified Titania with a Ruthenium(II) Complex and Silver Nanoparticles for Photocatalytic Degradation of Organic Compounds

Abstract

Abstract Ruthenium(II) complex with the phosphonate anchoring groups of [Ru(tbbpy)2(4,4′-(CH2PO3H2)2bpy)]2+ (RuIICP2, tbbpy= 4,4′-di-tert-butyl-2,2′-bipyridine) and silver nanoparticles (Ag NPs) were used as single or comodifiers on titania surface. For the dual modified titania, two deposition sequences were applied to obtain Ag/RuIICP2 and RuIICP2/Ag, in which at first ruthenium(II) or silver was deposited on titania, respectively. Diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed the existence of modifiers, and the effect of ruthenium(II) on the properties of Ag NPs regarding their crystallite sizes and oxidation states distributions. Photocatalytic activities of the modified titania were investigated for oxidative decomposition of acetic acid and 2-propanol, and anaerobic dehydrogenation of methanol. Under UV/Vis irradiation for the methanol dehydrogenation, co-modified titania of Ag/RuIICP2 showed the best activity, while for acetic acid degradation, singly modified titania with silver showed the highest activity. In contrary, under visible light irradiation, singly fabricated titania with ruthenium(II) complex possessed the highest photocatalytic performance for 2-propanol oxidation. For all the three tested photocatalytic degradation reactions, Ag/RuIICP2 exhibited better photocatalytic activities than RuIICP2/Ag, indicating the different properties caused by opposite deposition sequences, e.g., DRS indicated the smaller sizes of metal NPs and XPS suggested the binding of ruthenium(II) to Ag NPs for RuIICP2/Ag, which in consequence influenced the overall photocatalytic outcome.