Insight into the effect of the configuration entropy of additives on the Seebeck coefficient

Abstract

Thermogalvanic cells have attracted considerable attention because of their potential to directly convert waste heat into electricity by using redox reactions under continuous operation with a simple, cost-effective design. An increase in the Seebeck coefficient owing to the interactions between the redox ions and the additives has been reported in recent studies. The configuration entropy of the small additives coordinated to a large ion is calculated to analyze the Seebeck coefficient obtained from the entropy difference between the redox pairs. The recently reported increase in the Seebeck coefficient owing to the introduction of guanidinium (Gdm) or urea into the Fe(CN)₆⁴⁻/Fe(CN)₆³⁻ electrolyte is analyzed using the theoretical results. Furthermore, qualitative and quantitative analyses were also performed to determine the influence of the affinity for the additives on the entropy difference of the redox couples and on the Seebeck coefficient. This study also demonstrates the enhancement in the Seebeck coefficient caused by a membrane isolating the binding species into an appropriate hot/cold zone.