Poly(3,4‐Ethylene Dioxythiophene)/Poly(Styrene Sulfonate) Electrodes in Electrochemical Cells for Harvesting Waste Heat

Abstract

Low-grade waste heat can be harvested using electrochemical cells. However, the high cost of commonly used platinum electrodes limits their application. In this study, we report that poly(3,4-ethylene dioxythiophene)/poly(styrene sulfonate) (PEDOT/PSS) films as an attractive alternative to platinum electrodes, as they show a lower charge transfer resistance. Using ferricyanide/ferrocyanide as the electrolyte, the PEDOT/PSS-based thermoelectrochemical cell with dimensions of 5 cm  5 cm  2 cm delivered a maximum power output of 300 μW with 1 Ω loading at a temperature difference of ca. 30 K, which is sufficient for driving an array of light emitting diodes and Bluetooth humidity/temperature sensors for wireless communications. Furthermore, PEDOT/PSS offers the advantage of compatibility with insoluble redox couples such as Prussian blue analog materials, which facilitates determining the temperature-dependent redox potential of different materials. The appropriate combination of redox couples enables realizing thermally regenerative electrochemical cells. Power could be generated during an environmental temperature change; however, the temperature difference between different electrodes does not need to be maintained for these cells.

All-polymer wearable thermoelectrochemical cells harvesting body heat

“…Electrolyte systems were p-type: CMC-K 3/4 FeCN 6 , and n-type: PVA-FeCl 2/3 , respectively, with a system temperature difference (ΔT) of 10°C (T H = 35°C & T C = 25°C). Owing to the open and porous structure ( Figure 2 B) as well as the good wettability of PEDOT:PSS ( Wang et al., 2020 ), the thermocell made from the 3D printed PEDOT:PSS electrode exhibited an enhanced thermoelectrochemical performance compared to PEDOT:PSS film with increasing current from 8.2 A m −2 to 13.0 A m −2 and power density from 12.2 mW m −2 to 25 mW m −2 for n type and 15.2 A m −2 to 27.5 A m −2 and power density from 30.2 mW m −2 to 70 mW m −2 for p type ( Figures 2 C and 2D). In addition, the use of 3D electrodes also increases the open voltage compared to the 2D film electrode from 5.86 mV to 6.90 mV in n type device and from 7.40 mV to 9.21 mV in p type device.…”

“…For example, poly (3,4-ethylenedioxythio-phene): polystyrenesulfonate (PEDOT:PSS), one of the most popular CPs, has been reported to provide attractive alternative to platinum electrodes ( Yuk et al., 2020 ). Owing to a low charge transfer resistance, films of PEDOT:PSS showed performance that was comparable to carbon-based materials for a thermocell application ( Wang et al., 2020 ). However, current PEDOT:PSS electrodes are generally in a thin film form prepared via techniques including drop-casting ( Wang et al., 2020 ), ink-jet printing ( Perinka et al., 2013 ), and screen printing ( Sinha et al., 2017 ), in which the penetration of electrolyte, ion transfer rate and ion accessible surface area are greatly limited.…”

“…Owing to a low charge transfer resistance, films of PEDOT:PSS showed performance that was comparable to carbon-based materials for a thermocell application ( Wang et al., 2020 ). However, current PEDOT:PSS electrodes are generally in a thin film form prepared via techniques including drop-casting ( Wang et al., 2020 ), ink-jet printing ( Perinka et al., 2013 ), and screen printing ( Sinha et al., 2017 ), in which the penetration of electrolyte, ion transfer rate and ion accessible surface area are greatly limited. As a result, it is hard to further increase the performance (especially the current & power output) of the thermocell using these electrode configurations.…”

Unconventional Thermoelectric Materials for Energy Harvesting and Sensing Applications

“…Recently, Wang et al demonstrated a PEDOT:PSS-based thermo-electrochemical cell using ferricyanide/ferrocyanide as the electrolyte. This device delivered a maximum power output of 300 μW, with a 1 Ω loading at a temperature difference of 30 K; additionally, this device powered an array of light-emitting diodes and Bluetooth humidity/temperature sensors for wireless communication . Furthermore, they investigated the electrochemical properties of insoluble redox couples such as Prussian blue (PB) analogue compounds by hybridizing them with PEDOT:PSS via ball milling, drop-casting on a polystyrene mold, and heating at 70 °C for 24 h. In this work, they combined nickel ferrocyanide (NiHFC) with Fe 2+ /Fe 3+ using a cation separator (Figure a) and PB with K 3 Fe­(CN) 6 /K 4 Fe­(CN) 6 using an anion separator (Figure b).…”

3D‐Printed Wearable Electrochemical Energy Devices

“…Apart from carbon and carbon‐composite materials, conductive polymers are attracting interest as electrode materials for wearable thermocells owing to their low cost, light weight, ease of preparation, and most importantly, their flexibility. [ 101 ] Commonly used conductive polymers include polyaniline (PANI), polypyrrole (PPy), and poly(3,4‐ethylenedioxythiophene) (PEDOT). [ 112 ] PANI and PPy involve extensive synthesis processes while their conductivity and potential range are much lower than those of PEDOT, which limits their broader applicability.…”