STUDY OF THE ELECTROCHEMICAL PROPERTIES OF COMPLEX [Co(py-pz)4Z+ IN IMIDAZOLE-BASED IONIC LIQUIDS USING CYLIC VOLTAMMETRY METHOD

• Main Author: Utari, Riyadini
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/42151
• Institution: Institut Teknologi Bandung

Cobalt-based complexes can be used as redox mediators in DSSC replacing the IJ - 1- redox pairs because they have a reaction involving simple electron transfer, which is one electron and have the potential to reduce corrosives on the cathode metal. Meanwhile, ionic liquids can be used as solvents in DSSC because they have relatively high conductivity, wide potential range, non-flammability and high thermal stability. This characteristic makes ionic liquids have advantages over conventional electrolytes which are a combination of organic solvents and supporting electrolytes. Ionic liquids can be directly used as electrolytes without the addition of other additives. Therefore, a fundamental study of mass tran5fer rates, electrochemical properties and interactions between ionic liquid<i and cobalt complexes is needed before ionic liquids and cobalt complexes are used in DSSC applications. In this study, the study of the electrochemical properties of the tris (2 (!H-pyra:::ole-1-il) pyridine) cobalt (11) or [Co(py-p::)3p+ complex was carried out in various imida:::ole-based ionic liquids, i.e. [bmim}[BF4}, [bmim}[OTj}, [bmim}fNTfi}. [emim}[NTfi] dan [hmzm}[NTjij. Common organic solvents were chosen as a comparison, acetonitrile. The measurement method used was cyclic voltammetry with a variation of the scan rate (20-100 mvs -at variation of temperature (303-323 K). The diffusion coefficients of oxidation and reduction (D) and the electron transfer rate constant (ks) of the complex [Co(py-p:::J;F+ were determined using the Nicholson methods via the Randles-Sevcik equation. The activation energy required by the complex [Co(py-p::)Jp+ for diffusion (ED) and electron transfer (Eks) was determined via the Arrhenius equation. The results showed that based on cyclic voltammogram, the redox reaction of complex [Co(py­ p:::JJP+ was more quasi-reversible in ionic liquids than acetonitrile, indicated by the value of D.Ep in ionic liquids and acetonitril (290--150) mV and 730 mV, respectively. The difference in D.Ep in ionic liquids was caused by the low conductivity of ionic liquids Ionic liquids have advantages over organic solvents, which are higher conductivity, so they do not require supporting electrolytes. However, at low temperatures, the conductivity is usually lower than organic solvents with relatively large supporting electrolytes. The f Co(py-p:::)3F+ complex in acetonitril is more d?ffzcult to undergo oxidation than its reduction. The higher the temperature of the solutions, the rate of diffusion of oxidation and reduction of the complex [Co(py-p )3pwhich was measured more quickly due to the decrease in the viscosity of the solvent. The calculation results show the value of D in ionic liquids is I 00 times smaller than in acetonitrile. D values for the oxidation and reduction of the [Co(py-p )3pcomplex in ionic liquid'! (0.5- I0.5) x 10 8 cm2•s ' and (1-15) x 10 8 cm2 s 1 respectively. D values for the oxidation and reduction of the complex [Co(py-p::)3F+ in acetonitril (398-680) x IO 8 cm2 s 1 and (81I -II90) x I os cm2•s 1 respectively. The d[fference in the values of D oxidation and reduction due to the d[fferent Co2 + and Co3- radii after undergoing electron tramfer. Eo values of complex oxidation in ionic liquids and acetonitril was (-18.2- 60) kJmol -1 and 2I.6 k.Imoi- 1 respectively. The Eo reduction value of the complex in ionic liquids and acetonitril is smaller than the oxidation Eo values re5pectively (-12.6-55.2) k.Imol 1 and I5.8 kJmol 1 A lower ED value indicates that the complex [Co(py-p::)3] 2+ is easier to diffuse towards the electrode surface. This is consistent with the data D reduction value that was greater than the D oxidation value. The value of ks in the reaction [[Co(py-p::)3J2" 3+ in ionic hquids ((6.3-I2.3) x I0 -6 cm xwas smaller than acetonitril (53.4 x 10- 6 cm•s. The value of ks and ED wass influenced by the viscosity of the solvent and the type of cation/anion of the ionic liquid.