The
solubility of redox molecules is a critical factor that influences
cell performance in redox-enhanced electrochemical capacitors (redox
ECs). Unfortunately, commonly used organic redox molecules have low
solubility in aqueous systems, limiting further performance enhancements.
To solve this issue, a complex and costly synthesis is generally required.
Here, we introduce the concept of a hydrotropic-supporting electrolyte
(HSE) that can function as both a solubility-enhancing hydrotrope
and an ion-conducting supporting electrolyte. Using the HSE, the solubility
of hydroquinone (HQ) and anthraquinone-derivative (AQM-Br) increased
up to 7- and 3-fold, respectively, compared to that in the aqueous
H2SO4 electrolyte. We develop a high-performance
redox EC by implementing a bipolar AQM-Br with p-toluenesulfonic acid as the hydrotrope. Our mechanistic analysis
provides insight into correlating the solute–hydrotrope interactions
and hydrotrope efficiency. This work serves as a guideline for designing
energy-dense redox-active electrolytes and for optimal selection of
the HSE and redox-active electrolyte pairs.
Novel acetal-functionalized indacenodithiophene (IDT)
moieties
were developed in this study. Conductive polymers containing IDT units
are promising candidates for synthesizing high-performance thermoelectric
materials because their high charge-carrier mobility in the amorphous
state has the potential to reduce the thermal conductivity without
affecting its electric conductivity. Nevertheless, IDT-containing
polymers such as poly(indacenodithiophene-co-3,4-ethylenedioxythiophene)
(PIDT-EDOT) exhibit poor conductivity (0.43 S cm–1). Herein, we propose a novel strategy to control the dopant position
near the benzylic position of the polymer backbone via a Lewis acid–base
complex between a novel acetal-functionalized IDT (IDTa) unit and
a dopant, nitrosyl hexafluorophosphate. The PIDTa-EDOT polymer exhibited
an increase in doping efficiency and condensed π–π
stacking, which increased its electrical conductivity. Moreover, PIDTa-EDOT
exhibited a considerably lower thermal conductivity (0.09 W m–1 K–1) than that exhibited by PEDOT:PSS
(0.16–0.39 W m–1 K–1).
This was because of the reduced grain size of the polymer post doping.
Consequently, PIDTa-EDOT exhibited an ∼30-fold increase in
electrical conductivity (12.56 S cm–1) and an ∼6-fold
increase in thermoelectric performance (ZT = 7.57 × 10–3) compared to those exhibited by PIDT-EDOT. Our research offers a
new approach to increase electrical conductivity and decrease thermal
conductivity simultaneously. This ultimately leads to the development
of a high-performance thermoelectric material.
A cost-effective, flexible, and transparent gas barrier has been a main pursuit of research into plastics electronics. However, it is difficult to realize a highperformance gas barrier on a plastic substrate via a solution process at low temperature. Here, by introducing an interfacial photocatalytic reduction between TiO x and graphene oxide (GO) films, a solution-processed and transparent gas barrier film is demonstrated using reduced GO (rGO)/TiO x . A dramatic photochemical reduction of GO occurs at the interface between TiO x and the GO film under ultraviolet irradiation, which allows the fabrication of dense and uniform gas barrier films via a solution process at temperatures below 100 °C. In addition, the closely packed structure in the rGO film results in a decreased water vapor transmission rate (WVTR) of 0.37 g m −2 day −1 even with a thin rGO (<13 nm)/TiO x (7 nm) film, leading to a high transmittance of over 80% in the visible range.
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