Photochemical hydrogen evolution from aqueous triethanolamine solutions sensitized by binaphthol-modified titanium(IV) oxide under visible-light irradiation

Abstract

Surface modification of titanium(IV) oxide (TiO 2 ) powders with 1,1'-binaphthalene-2,2'-diol (bn(OH) 2 ), having two phenolic hydroxyls and atropisomeric chirality, in refluxed ethanol led to the formation of a deep yellow-colored surface complex, giving visible-light absorption at a wavelength below ca. 550-600 nm.Quantitative analyses of the surface complex revealed that absorption intensity at 450 nm in diffuse reflection measurement was almost proportional to its amount and that its amount depended strongly on the amount of surface hydroxyl groups of TiO 2 but not on the crystal structure of TiO 2 , anatase and rutile. The bn(OH) 2 complexation was also applied to platinized TiO 2 to drive photocatalytic molecular hydrogen (H 2 ) evolution from 1 deaerated triethanolamine solutions under visible-light irradiation at a wavelength even longer than 540 nm. The photonic efficiency of the photocatalytic reaction at 450 nm was estimated to be 0.02% for bn(OH) 2 -modified TiO 2 (JRC-TIO-3) loaded with 0.1 wt% of platinum. On the basis of these experimental results, the reaction mechanism, which involves visible-light excitation of the surface complex, injection of electrons from the complex to TiO 2 , and migration of the electrons to platinum deposits, where reduction of H + takes place to give H 2 , was elucidated.

Preparation of Dihydroxy Naphthalene/TiO2Complex via Surface Modification and Their Photocatalytic H2Production Performances Under Visible Light

“…Among the literatures reported Pt/TiO 2 catalyst for H 2 production, the optimal Pt contents were mainly in the region of 0.1-2 wt %. 15,23,36,39 However, in this investigation, no obvious H 2 production increase was observed when the Pt content beyond 0.02 wt %. This optimal Pt content is much lower than that in the previous reports, indicating such Pt loaded dihydroxy naphthalene/TiO 2 system can dynamic decrease the noble metal content which is beneficial to decrease the cost.…”

“…22 However, only a few literature reported on the photocatalytic H 2 production by organic modified TiO 2 -based catalyst. 23 Ikeda et al 23 reported the photochemical hydrogen evolution from aqueous triethanolamine solutions sensitized by binaphthol-modified TiO 2 loaded with 0.1 wt % Pt under visible light. They proposed that visible-light excitated the surface complex, inject the electrons from the complex to TiO 2 , and migrate the electrons to platinum deposits, where reduction of H + takes place to give H 2 .…”

“…31,32 It has been reported that Ti-OH reacts with a phenolic groups of organic compounds, such as catechol, 33 salicylic acid, 34 and binaphthol, 35 to form Ti-O-C bonds on the TiO 2 surface. It is therefore possible that the TiO 2 surface is modified by the formation of Ti-O-C bonds rather than by physical adsorption of dihydroxy naphthalene.…”

Degradación Fotocatalítica de Contaminantes Orgánicos Presentes en Agua Residual de la Industria Litográfica mediante Oxido de Bismuto(NI)/Oxido de Titanio (Bi2O3/TiO2)

“…Con el fin de aumentar su actividad, una de las estrategias es la generación de nuevas especies oxidantes bajo el rango visible y evitar la recombinación de par electrón/hueco, fenómeno indeseable en los procesos fotocatalíticos. Lo anterior se puede lograr a través del dopado con metales de transición u otro elemento dopante, y el uso de semiconductores acoplados (Ikeda et al, 2003;Iliev et al, 2003;Gurunathan, 2004). Ejemplos de sistemas semiconductores acoplados que han sido utilizados para tal fin son CdS/TiO2 (Li et al, 2010), ZnO/TiO2 (Ge et al, 2009), SnO2/TiO2 (Hou et al, 2007), SiO2/TiO2 (Cetinkaya et al, 2013), Fe2O3/TiO2 (Banisharif et al, 2015, Galeano et al, 2013, entre otros, y mostraron adecuados niveles de degradación de varios compuestos orgánicos.…”

Photocatalytic Activities of TiO2 Modified by Poly(fluorene- co-bithiophene) under Visible Light

“…It should be pointed out that the simple physical absorption of the dyes on the surface of TiO 2 is not tight enough because the dyes are always readily dissolved in water, the change in degradation induced by change of pH value of the reactive solution was linear with the concentration of dye adsorbed onto TiO 2 [14] A costly way is to synthesize the modified TiO 2 with chemical bond formation between dye and TiO 2 [15,16]. We developed another simple way of using conjugated polymers Poly(fluorene-co-thiophene)s (PFT) as photosensitizer [17] and attracted wide attention [18].…”