Electrochemical Properties of Al Doped Polypyrrole Composite Polymer: Mott-Schottky Approximation and Density Functional Theory

Polypyrrole and Al doped polyprrole thin films were synthesized by electrochemical deposition method. FTIR spectroscopic studies confirm the formation of PPy and Al:PPy thin films. From the FESEM crosssectional images, film thickness were measured as 393.9 and 425.0 nm for the PPy and Al doped PPy thin film, respectively. Electrochemical properties of the deposited polymers are studied by Mott-Schottky analysis and electrochemical impedance spectroscopy. The calculated acceptor concentration is 5.03 × 1018 m−3 and 5.14 × 1018 m−3 for PPy and Al:PPy thin film, respectively. EIS analysis are performed to find out the effect of aluminum doping on PPy matrix. An equivalent circuit model is fitted to the EIS data to understand the behavior of coating/electrolyte interface and to determine the values of the circuit elements. Time-dependent self-consistent field and density functional theory based on CAM-B3LYP level with 6-311G(d,p) basis set are used to compute electronic properties such as HOMO and LUMO energies, ionization potential, electron affinity, electronegativity, hardness, softness. Electronic energy levels of the synthesized polymers are represented using the results of Mott-Schottky studies, and the frontier energy levels are also illustrated in this energy diagram to give more detailed explanation.