463490 Electrochemical Behavior of Ni2bpy(TPTZ)2 Complex on Carbon Paste Electrode Modified with Nanocrystalline ZnO Powder for Usability in Dye-Sensitized Solar Cells
In this study, chemical structure of Ni(II) complex with the mixed N-donor ligands 2,2’-bipyridyl-1,3,5-tripyridyl-striazine (TPTZ) and Bpy was electrochemically determined using different metal/ligand ratios. The square-wave voltammetry (SWV) results on glassy carbon electrode (GCE) confirmed that Ni2Bpy(TPTZ)2complex was stable at pH 7.8 in phosphate buffer. The electrochemical behavior of the complex was investigated using a conventional three-electrode system, consisting of carbon paste (CPE) and ZnO modified carbon paste (ZnO/CPE) working electrodes to understand its possible use as a redox mediator and/or sensitizer in DSSCs.
The mechanisms of the electrode processes were elucidated by using SWV and cyclic voltammetry (CV) techniques. The number of electrons transferred in the electrode processes (n) and transfer coefficients (α) was determined from the effect of frequency on the SW voltammograms. Two reduction peaks were observed on the SWVs at both electrode surfaces whereas a quasi-reversible redox couple appeared corresponding to anodic oxidation of central Ni(II) ion on ZnO powders. The scan rate dependence of the peak currents and potentials showed that electrode process was adsorption controlled. The rate constant for oxidation process was found to be much faster than the reduction one suggesting that electron injection from the excited complex to the ZnO nanoparticles may also be greater than the recombination with the oxidized complex in DSSCs.
It can be concluded that the complex can be employed as a photosensitizer for ZnO powder photoanode as well as the redox mediator in DSSCs used CPE cathode.
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