Catalytic water oxidation using chemically generated Ru(bpy)33+ oxidant

Catalytic water oxidation to evolve O-2 was studied using chemically generated Ru(bpy)(3)(3+) (bpy; 2,2'-bipyridine) oxidant, Ru(bpy)(3)(2+) was oxidized to Ru(bpy)(3)(3+) by suspension of PbO2 powders. In the catalytic water oxidation system composed of the Ru(bpy)(3)(3+) and RuO2 adsorbing Ru-red ([(NH3)(5)Ru-O-Ru(NH3)(4)-O-Ru(NH3)(5)]Cl-6), much higher amount of O-2 evolved than in a homogeneous Ru(bpy)(3)(3+)/Ru-red system. This was ascribed to the suppression of the bimolecular decomposition of Ru-red in the RuO2 matrix. The amount of the O-2 evolved increased with the adsorbed amount of the Ru-red into RuO2, wkereas higher amount of the adsorbed Ru-red resulted in the decrease of the O-2 evolution, which was ascribed to bimolecular decomposition of Ru-red in the RuO2 at higher concentrations. The activity of Ru-red in the RuO2 matrix was analyzed considering a static distance distribution between the nearest-neighboring molecules. The decomposition distance (r(d)) was obtained as 1.25 nm showing that contacting Ru-red molecules undergo bimolecular decomposition without catalysis. (C) 1999 Elsevier Science B.V. All rights reserved.