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 TiO 2 surfaces have been investigated. Langmuirian binding constants for FTO and TiO 2 are estimated to be 3 × 10 6 M −1 and 4 × 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 TiO 2 -adsorbed dye. Degradation of the Z907 dye affects the electron hopping conduction at the FTO–TiO 2 interface.