Effect of aluminum reinforcement on the structural, physicochemical, and electrochemical properties of polyaniline-derived polymer/aluminum composites by in situ polymerization

Abstract

We investigated the structural, conductive, and electrochemical properties of polyaniline-derived polymer/pristine aluminum composites by in situ polymerization. This research focused on the conductivity and electrochemical energy storage effects of Al particles used as reinforcing elements in composites and elucidating the interaction of polyaniline on the surface of Al particles by keeping the HCl acid dopant concentration and monomer-oxidant ratio constant. FTIR results revealed that polymerization was successfully synthesized by showing all the characteristic peaks of polyaniline, and the polymer matrix of composites produced in the presence of aluminum was polyaniline. SEM images also showed that Al particles were completely embedded or enclosed in the polymer matrix. Conductivity measurements revealed that the inclusion of Al particles with different mass ratios in the polyaniline matrix resulted in a decrease in conductivity compared to pure polyaniline, and these results were likely due to the thin yet highly stable and electrically-resistant protective oxide (Al2O3) film layer that rapidly formed on the aluminum surface in solution with low HCl concentration. Electrochemical characterizations of polyaniline and composites were investigated by galvanostatic charge discharge, cyclic voltammetry, and electrochemical impedance spectroscopy method. The results showed that composites produced with different aluminum content did not have good supercapacitor properties compared to pure polyaniline, due to the rapidly-forming surface oxide film layer which prevented an effective interaction between the polymer matrix and Al particles. Consequently, the composite has not contributed to the increase in capacitance with aluminum loading by redox reactions at the interfaces with functional groups. This confirms that the aluminum incorporated does not interact with the matrix structures of the composites, but is found in composites with a stable and protective passive oxide film layer that rapidly forms on its surface, thus having higher corrosion protection effectiveness.