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′-(CH 2 PO 3 H 2 ) 2 bpy)] 2+ (Ru II CP2, 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/Ru II CP2 and Ru II CP2/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/Ru II CP2 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/Ru II CP2 exhibited better photocatalytic activities than Ru II CP2/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 Ru II CP2/Ag, which in consequence influenced the overall photocatalytic outcome.

Silver-modified octahedral anatase particles as plasmonic photocatalyst

“…1 c) confirmed anatase form of titania and silver in two crystalline forms: Ag and Ag 2 O. The presence of Ag 2 O is not surprising since silver is easily oxidized, and even when zero-valent silver is formed (under anaerobic conditions), the contact of metallic silver with air results in surface oxidation of silver [46] , [53] , [54] , [55] , [56] . The crystallite sizes of zero-valent silver are shown in Table 1 .…”

Noble metal-modified faceted anatase titania photocatalysts: Octahedron versus decahedron

“…Therefore, various methods have been applied to enhance activity and stability of plasmonic photocatalysis, e.g., by extension of photoabsorption range (light harvesting), i.e., (i) preparation of NPs of various sizes and shapes [ 76 ], (ii) composed of two noble metals (e.g., Au-Ag, Ag-Cu, Ag-Pt, Au-Pd, Ag-Pd) [ [77] , [78] , [79] , [80] , [81] ], or (iii) combined with homogeneous photocatalysts (e.g., Ru complexes) [ 82 , 83 ]. Although, resultant photocatalysts have shown better photoabsorption properties, in many cases a decrease in vis photocatalytic activity has been observed since second modifier works as a recombination center [ [82] , [83] , [84] , [85] ]. Recently, another method of activity enhancement has been proposed, i.e., nano-architecture design of plasmonic photocatalysts, such as deposition of NMNPs in/on the structure of aerogels [ 86 ], mesocrystals [ 87 ] and facetted titania.…”

Noble metal-modified titania with visible-light activity for the decomposition of microorganisms

“… a crystal phase (r: small content of rutile and a: small content of anatase), b crystallite size of the dominant titania phase, c content of electron traps, d specific surface area, e crystallite size of metal NPs, f,g data reported previously in [ 56 – 57 ], respectively. …”