A Polyaniline-Deposited Nonplatinum Metal as a Potentiometric Sensor—An Inexpensive Alternate to Conventional Platinum for Some Potentiometric Redox Reactions

For the purpose of employing an inexpensive alternative to conventional platinum for use by upper-division as well as graduate students, polyaniline (PANI)-deposited stainless steel (SS) and mild steel (MS) electrodes are described as indicator electrodes for potentiometry and potentiometric titrations of some redox reactions. PANI is deposited on the nonplatinum metal by electrochemical polymerization of aniline using cyclic voltammetric technique. Alternate methods to produce the PANI electrodes are also suggested. The electrodes respond to concentration changes of hydroquinone (H₂O), Fe²⁺/Fe³⁺, and Fe(CN)₆]^4–/Fe(CN)₆]^3– in HCL electrolytes, and the potential variation with concentration follows the Nernst relationship. Under identical experimental conditions, the response time of the PANI/SS, PANI/MS, and Pt electrodes for a change in concentration of Fe³⁺ in a mixed electrolyte of Fe²⁺ and Fe³⁺ is found to be about 20 s. Neutralization reaction of HC1 versus NaOH, redox reaction of Fe²⁺ and Ce⁴⁺, and redox reaction of Fe²⁺ and KMnO₄ in several concentrations in the range from 1 mM to 100 mM are carried out using the PANI/SS, PANI/MS, and Pt indicator electrodes. The performance of the PANI/SS and PANI/MS electrodes is as good as that of the Pt at all concentration levels of the titrations. The electrodes can be reused for several titrations by storing them in an acid electrolyte for a long period of time. Thus, the conventional inert Pt or Au can be substituted for by using a PANI-deposited nonplatinum reactive metal as a potentiometric sensor for redox titrations.