The Interfacial Effect on the Open Circuit Voltage of Ionic Thermoelectric Devices with Conducting Polymer Electrodes

Abstract

Organic‐based energy harvesting devices can contribute to a sustainable solution for the transition to renewable energy sources. The concept of ionic thermoelectrics (iTE) has been recently proposed and motivated by the high values of thermo‐voltage in electrolytes. So far, most research has focused on developing new electrolytes with high Seebeck coefficient. Despite the major role of the electrode materials in supercapacitors and batteries, the effect of various electrodes on energy harvesting in iTE devices has not been widely studied. In this work, the conducting polymer poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is investigated as the functional electrodes in iTE supercapacitors. Through investigating the thermo‐voltage of iTEs of the same electrolyte with varying composition of PEDOT electrodes, it is identified that the different PSS content greatly affects the overall thermo‐induced voltage coefficient, Seff (i.e., effective thermopower). The permselective polyanion in the electrode causes cation concentration differences at the electrode/electrolyte interface and contributes to an interfacial potential drop that is temperature dependent. As a result, the overall thermo‐voltage of the device possesses both an interfacial and a bulk contribution. The findings extend the fundamental understanding of iTE effect with functional electrodes, which could lead a new direction to enhance the heat‐to‐electricity conversion.

Interfacial Effect Boosts the Performance of All‐Polymer Ionic Thermoelectric Supercapacitors

“…This results in the potential step at the interface demonstrated previously. [ 16 ] It is also possible that the contact of the ion gel with PEDOT:PSS triggers some internal reorganization in PEDOT:PSS and PVDF‐HFP to minimize the surface energy, thus resulting in an interfacial dipole. We thus propose a potential profile in the device under the temperature gradient as illustrated in Figure 3b‐ii, where both the ionic Seebeck effect and Donnan exclusion interfacial effect would add their contribution to enhance the total thermovoltage.…”

“…In our recent work, we discovered that the ionic‐electronic mixed conductor based on the polymer blends poly(3,4‐ethylendioxythiophene):polystyrene sulfonate (PEDOT:PSS) can provide an additional contribution as electrodes in ITESCs. [ 16 ] PEDOT is a p‐doped π‐conjugated polymer that conduct electronic charge carriers, while PSS is an ionic conductor transporting cations. PEDOT:PSS acts as an electrode by connecting the electrolyte to the external circuit through its electronic conduction.…”

3D cellulose fiber networks modified by PEDOT:PSS/graphene nanoplatelets for thermoelectric applications

“…This additive improves the electrical properties of PEDOT:PSS 17 . Moreover, we introduced a cross-linking agent 3-glycidoxypropyltrimethoxysilane (GOPS) to the conductive polymer solution which improves the chemical stability and promotes the environmental stability of PEDOT:PSS without significantly affecting the electrical properties 13,18,19 . Indeed, the composites show excellent stability of their electrical properties even after three months at ambient conditions, and high flexibility suitable for fabricating self-supporting layers, which can be easily transferred onto curved, and bendable surfaces.…”

Thermally Chargeable Supercapacitor with 3D Ti3C2Tx MXene Hollow Sphere Based Freestanding Electrodes

“…[22][23][24] TCSC devices requiring no special charge circle or equipment compensate for the lack of the energy storage harvested by the TE, accomplishing the fabrication of selfpowered devices. Thermoelectric devices that determine the Seebeck coefficient are mainly divided into electronic conductors and ionic conductors [25][26][27] types. The latter one has attracted a lot of attention because of the higher Seebeck coefficient than electronic conductors by several orders in magnitude.…”