Energy harvesting by neutralization pseudocapacitor obtained from phosphomolybdic acid and poly(3,4-ethylenedioxythiophene)

Abstract

This study proposes the use of pseudocapacitors obtained from self-assembled materials to harvest energy after complete charge/discharge cycles conducted in electrolytic solutions with different pH values. The negative electrode consisted of phosphomolybdic acid (PMA), poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS), and polyallylamine (PAH), whereas the positive electrode comprised electrosynthesized PEDOT. The ability of these electrodes to harvest energy resulted from the partial change in entropy associated with alterations in the proton concentration after neutralization reactions. Investigation of the potentiodynamic profile of the current density and conduction of electrochemical impedance spectroscopy helped to evaluate the practical reversibility of the proton electroinsertion process and to maximize the energy storage efficiency. The electrochemical quartz crystal microbalance data allowed for proposal of a charge compensation mechanism and for assessment of the proton selectivity of the modified electrodes. On the basis of the charge/discharge curves recorded from pH=1 to pH=6, the neutralization pseudocapacitor harvested 30.7kJ per mol of electroinserted proton during H2SO4 solution neutralization, which corresponded to 54.6% of the neutralization enthalpy. Together, these results demonstrated the viable application of this methodology to harvest energy during acid wastewater treatment.