Proportionality between electrochemical thermopower and mass fraction in PEDOT:PSS / AC model binary supercapacitor electrodes

Abstract

Recent progress in electrochemical waste heat harvesting technology has drawn attention owing to its high thermopower, typically > 1 mV/K, leading to high heat-to-electricity conversion efficiency. One of the key merits is that it can adopt chemistry and manufacturing techniques from already existing supercapacitors. However, they typically require electrodes in composite forms and the rule that determines the electrochemical thermopowers of such composites remains unknown to this date. This work experimentally demonstrates that the electrochemical thermopower of the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) / activated carbon (AC) model composite electrode is proportional to mass fraction of the respective constituents. This rule imposes a ceiling in the electrochemical thermopower of composites, where the largest thermopower among the constituents is the maximum that the composite can possibly achieve. This proportionality rule can serve as a design guideline for electrochemical heat harvesters deriving from supercapacitors in the future.