Effect of Cation on Dye Regeneration Kinetics of N719-Sensitized TiO2 Films in Acetonitrile-Based and Ionic-Liquid-Based Electrolytes Investigated by Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) in the feedback mode has been used to investigate the kinetics of dye regeneration on cis-di(thiocyanato)-bis(2,2'-bipyridyl-4,4 ''-dicarboxylate) ruthenium(II)-sensitized TiO2 photoelectrochemical electrodes in contact with room temperature ionic liquids electrolytes. Acetonitrile based electrolytes were used for comparison. The data are analyzed with the help of a revised model for relating steady state approach curves in the SECM feedback mode to an effective rate constant for the dye regeneration process. This effective rate constant summarizes the effect of electron transfer kinetics, mass transport of the mediator inside the porous electrode, and recombination processes. We found a remarkable dependence of the dye regeneration on the nature and concentration of deliberately added cations.