The coverage control and electric desorption kinetics of polypyridyl ruthenium dye molecule fixed on the interface of nanoporous TiO2

This paper conducted researches on electric desorption kinetics, desorption mechanism and quantitative desorption of the adsorbed polypyridyl ruthenium based dye on the surface of nanoporous TiO2 film under negative potential. Change external negative potential to obtain the relationship between dye desorption amount of sensitized-TiO2 film and potential. After the negative potential exceeds about −0.5 V, amount of dye left on the surface of TiO2 film decreases rapidly. According to the pseudo-first-order kinetic equation, dye desorption rate kd under potential of −0.6 V is 6.92 × 10−3 s−1. Research the relationship between the amount of desorbed dye and the potential duration, ionic concentration in supporting electrolyte solution as well as film thickness. It implies that the amount of adsorbed dye can be accurately controlled. Based on the measurement and analysis of the adsorption property of desorbed dye through UV-Visible absorption spectroscopy, there is no change of number of absorption peaks of the desorbed dye or no occurrence of new peak, while the absorption peak position of the desorbed dye shows a blue shift. Cyclic voltammetry is used to research the TiO2/dye/electrolyte interface and TiO2/electrolyte interface, and analyze the influence of dye desorption on the cyclic voltammetric response. Two possible dye desorption mechanisms are provided: one is the fracture of ester bond between dye and TiO2 under negative potential; another is the electrostatic repulsion desorption mechanism. Work in this paper is of theoretical guiding significance for compounding new dyes, defining assembly mechanism of dye, enhancing the stability of solar cell, and improving solar cell efficiency.