Visible-light-sensitized production of hydrogen using perfluorosulfonate polymer-coated TiO2 nanoparticles: An alternative approach to sensitizer anchoring

Abstract

TiO2 sensitized by derivatized ruthenium bipyridyl complexes has been intensively investigated as a tool to utilize visible light. This article describes an alternative approach to attaching ruthenium complex sensitizers at the TiO2/H2O interface, which is a much simpler and more efficient way to produce hydrogen. The surface of TiO2 particles are simply coated with perfluorosulfonate polymer (cation-exchange resin: Nafion), and then Ru(bpy)(3)(2+) (as a cationic form), whose bipyridyl ligands are not functionalized with carboxylic acid groups, are bound within the Nafion layer through electrostatic attraction. The visible-light-induced production of H-2 on Nf/TiO2 using simple Ru(bpy)(3)(2+) as a sensitizer is far more efficient than that on Ru(dcbpy)(3)-TiO2, upon which many sensitized photoelectrochemical conversion systems are based. Effects of various experimental parameters such as pH, concentration of Ru(bpy)(3)(2+), Nafion loading, and the kind of TiO2 were investigated. Under optimized conditions, the H-2 production rate was about 80 mu mol/h, which corresponds to an apparent photonic efficiency of 2.6%. The roles of the Nafion layer on TiO2 in the sensitized H, production are proposed to be twofold: to provide binding sites for cationic sensitizers and to enhance the local activity of protons in the surface region.