Adsorption and redox chemistry of cis-RuLL'(SCN)(2) with L=4,4'-dicarboxylic acid-2,2'-bipyridine and L'=4,4'-dinonyl-2,2'-bipyridine (Z907) at FTO and TiO2 electrode surfaces

The electrochemical and spectroelectrochemical properties of the sensitizer dye Z907 (cis-RuLL'(SCN)(2) with L=4,4'-dicarboxylic acid-2,2'-bipyridine and L'=4,4'-dinonyl-2,2'-bipyridine) adsorbed on fluorine-doped tin oxide (FTO) and TiO2 surfaces have been investigated. Langmuirian binding constants for FTO and TiO2 are estimated to be 3 x 10(6) M-1 and 4 x 10(4) M-1, respectively. The Ru(III/II) redox process is monitored by voltammetry and by spectroelectrochemistry. For Z907 adsorbed onto FTO, a slow EC-type electrochemical reaction is observed with a chemical rate constant of ca. k = 10(-2) s(-1) leading to Z907 dye degradation of a fraction of the FTO-adsorbed dye. The Z907 adsorption conditions affect the degradation process. No significant degradation was observed for TiO2-adsorbed dye. Degradation of the Z907 dye affects the electron hopping conduction at the FTO-TiO2 interface.