Composite Aerogel of Electropolymerized Polyaniline and SWCNTs with High Thermoelectric Performance

Abstract

Aerogels are promising in the preparation of high-performance thermoelectric (TE) materials due to their ultralow thermal conductivity. However, the TE performance of aerogels remains unsatisfactory. Herein, polyaniline/single-walled carbon nanotubes (PANI/SWCNT) composite aerogel with high thermoelectric performance is synthesized through dynamic three-phase interfacial electrochemical polymerization of aniline and subsequent physical mixing of PANI with SWCNTs followed by liquid nitrogen quenching and freeze-drying. By adjusting the content of SWCNTs, the PANI/SWCNT aerogel (50 wt% SWCNTs) achieves a high power factor (PF) of 73.33 ± 2.03 μW m −1 K −2 . The ultralow thermal conductivity of around 2.30 × 10 −2 W m −1 K −1 for the composite aerogel is superior to that of most conventional organic TE materials, rendering an excellent figure of merit (ZT) value of ≈0.95 at room temperature and great potential in improving TE performance of organic and organic/inorganic composites. Thermal treatment of the composite aerogel further enhances the PF to 96.28 ± 1.89 μW m −1 K −2 . This work provides an effective method in the formation of PANI/SWCNT TE composites and it puts forward insights into the preparation of other high-performance TE composites.

Compositing Nanostructured Polyaniline with Single-Walled Carbon Nanotubes for High Thermoelectric Performance

“…The formation of aggregations and bigger bundles, however, suggests poor dispersion of SWCNTs overloading above 50 wt%, which results in low conductivity and Seebeck coefficient. This is in line with the outcomes shown in Figure 4 as well [29]. Moreover, the electrical conductivity and Seebeck coefficient are interdependent; for example, the conductivity increased, and the Seebeck coefficient decreased through the enhancement of doping level [41].…”

“…With the introduction of SWCNTs, the characteristic peak of PANI can also be detected in the PANI-DMSO/ SWCNT composite films, but the broad peak at 19.6 °has been converted into conventional characteristic peaks at 17.4 °and 20.4 °, respectively. Meanwhile, the weakening for the peak at 20.4 °and sharpening for the peak at 25. particles and SWCNTs by the presence of SWCNTs [29]. In addition, the rising peak at 22.8 °representing a periodicity caused by π-π stacking of PANI/SWCNT-linked structures further confirms the existence of stronger interface interaction, hence improving TE performance effectively by facilitating carrier transport.…”

“…Notably, the Raman peaks of SWCNTs dominate that of the PANI/SWCNT composite, from which it can be inferred that the fundamental backbone of the composite films is composed of SWCNTs. And after pressing, the decline in the intensity of the typical peaks at 1640 cm -1 and 1490 cm -1 (Figure 6(c)), the blue shift of Gband, and the increment of the G/D ratio (Figure 6(d)), suggest stronger π-π-conjugated interaction between PANI and SWCNTs [29,46]. Furthermore, the temperature-dependent variation in the TE properties of PANI-DMSO/SWCNT composite films is investigated in the range of 25-145 °C (Figure 7(a)).…”

“…XRD is used to characterize the crystal structures of PANI-CK, PANI-CYH, PANI-CCl4, PANI-MB, PANI-DCM, and PANI-DMSO. The pristine PANI powders have three characteristic peaks that appear at about 2θ = 14:6 °(the repeat unit of the PANI chain), 20.4 °(the periodicity perpendicular to the polymer backbone chains), and 25.5 °(the periodicity parallel with the polymer backbone chains) [28,29]. The three characteristic peaks mentioned above correspond to (011), (020), and (200) crystal planes of PANI in sequence [30].…”

Advances in Thermoelectric Composites Consisting of Conductive Polymers and Fillers with Different Architectures

“…Carbon nanotubes, including single-walled carbon nanotubes (SWCNTs) with a diameter of 1–2 nm formed by curling a layer of graphene and multi-walled carbon nanotubes (MWCNTs) with a diameter range of several to hundreds of nanometers formed by curling multilayers of graphene, possess high conductivity, stretchability, and tenacity, demonstrating great potential as flexible TE materials confirmed by theoretical prediction and experimental results ( Figure 8 ) [ 66 , 67 ]. Because of the unique structure of CNTs, they have obvious advantages in using charge transfer doping to adjust the charge carrier density, as well as excellent electrical and mechanical properties and large specific surface area, thus providing new ideas and directions for the development and preparation of high-performance flexible TE materials and devices [ 46 , 68 , 69 ]. In past decades, CNTs have evolved into the mainstream fillers in TE composites following these reasons: (1) high electrical conductivity to enhance TE efficiency; (2) large specific surface areas to form highly efficient interface; (3) ability to coat polymers on their surface to reduce thermal conductivity; (4) carbon-based TE composites with flexibility, environmental friendliness, biocompatibility, and low-cost [ 8 , 70 , 71 , 72 ].…”