Electrochemical activity of polyaniline based on mixed dopants and cation movement toward high pH region

Two kinds of polyaniline (PANi) films have been comparatively studied for their electrochemical activity in HCl/NaCl aqueous electrolyte. A standard film of PANi/NMP was prepared by casting PANi from N-methyl pyrrolidone (NMP) solution. The other film of PANi/DBS was prepared from PANi dissolved in mixed solution of dodecylbenzene sulfonic (DBS) and dichloroacetic acids. The PANi/NMP film increased in the weight and volume upon oxidation, indicating anion movement. The weight uptake measured by quartz crystal microbalance and strain were approximately agreed with the number and volume of doped anions (Cl−) estimated from cyclic voltammogram. On the other hand, PANI/DBS film increased in the weight upon reduction. The correspondence between weight uptake and electronic charges during reduction indicated Na+ movement. Although the PANi/NMP showed electrochemical activity at pH < 2, the PANi/DBS was active up to pH5. Namely, the large DBS anion was immobilized in PANi network, resulting in cation movement and higher pH activity.