Microstructure and Thermoelectric Characterization of Composite Nanofiber Webs Derived from Polyacrylonitrile and Sodium Cobalt Oxide Precursors

Abstract

We report the microstructure and thermoelectric properties of composite nanofiber webs, which were fabricated by dual-electrospinning of polyacrylonitrile (PAN) and sodium cobalt oxide (NaCo2O4) precursor solutions with different input compositions and following heat-treatment at 600–900 °C for simultaneous carbonation and calcination. The SEM and EDS mapping images revealed that PAN-derived carbon nanofibers (CNFs) and NaCo2O4-based ceramic nanofibers coexisted in the composite nanofiber webs and that their relative contents could be controlled by the input compositions. The Seebeck coefficient increased from ~26.77 to ~73.28 μV/K and from ~14.83 to ~40.56 μV/K with increasing the relative content of NaCo2O4 nanofibers in the composite nanofiber webs fabricated at 700 and 800 °C, respectively. On the other hand, the electrical conductivity of the composite nanofiber webs increased with the decrement of the relative content of NaCo2O4 nanofibers as well as the increment of the heat-treatment temperature. Owing to the opposite contributions of NaCo2O4 nanofibers and CNFs to the Seebeck coefficient, electrical conductivity and thermal conductivity, a maximum power factor of ~5.79 μW/mK2 and a figure of merit of ~0.01 were attained for CNF/NaCo2O4-based composite nanofiber webs fabricated at 45 wt% input composition of NaCo2O4 and at heat-treatment of 700 °C.

Synthesis and characterization of conjugated PVA/PANi blend doped with functionalized Graphene for Thermoelectric Applications

“…It is clear that all prepared films are n-type semiconductors due to the negative Seebeck coefficient. However, the negative (-) sign identifies the type of the charge carrier, not the Seebeck coefficient value [38]. The figure shows that the Seebeck coefficient increases steadily with the temperature increasing for all the prepared samples.…”

New Progress on Fiber-Based Thermoelectric Materials: Performance, Device Structures and Applications

“…The Ag nanowire/PEDOT: PSS-coated yarns exhibited a high conductivity of ~320 Scm −1 and excellent robustness after washing, which was attributed to a strong electrostatic interaction between the PEDOT: PSS coating and the silk [ 108 ]. In addition, PAN and NaCo 2 O 4 can be fabricated into composite nanofiber webs by dual electrospinning [ 109 ]. At a fabrication temperature of 700 °C, the Seebeck coefficient of composite nanofiber web increased from ~26.77 to ~73.28 μVK −1 with the increase in relative content of nanofibers [ 109 ].…”

“…In addition, PAN and NaCo 2 O 4 can be fabricated into composite nanofiber webs by dual electrospinning [ 109 ]. At a fabrication temperature of 700 °C, the Seebeck coefficient of composite nanofiber web increased from ~26.77 to ~73.28 μVK −1 with the increase in relative content of nanofibers [ 109 ]. Furthermore, PEDOT: PSS/Te NW/CuTe nanocomposite [ 110 ], Sb 2 Te 3 /PAN yarn [ 111 ], and other hybrid fibers were researched to explore a high-performance TE fiber.…”

Regulating Na Occupation to Introduce Non-Fermi-Liquid States of NaxCoO2 for Enhanced Water Oxidation Activity

“…We notice another strongly correlated electron system, the layered sodium cobalt oxide (Na x CoO 2 ), has been reported as a high-efficient OER catalyst recently. − This material is discovered in the 1970s, with anomalously high thermopower, , superconductivity when intercalated with water, , unexpected metal–insulator transition, and its NFL states. , The lattice is composed of stacked layers of edge-sharing CoO 6 octahedra with inserted Na ions, where the charge carriers are confined in unusually narrow spaces, driving the system toward new quantum phases . In the CoO 2 slabs (without Na), each octahedrally coordinated Co atom is quadrivalent (Co 4+ : t 2g 5 e g 0 ), and the material is speculated to be a Mott insulator due to strong on-site Coulomb interactions.…”

“…We notice another strongly correlated electron system, the layered sodium cobalt oxide (Na x CoO 2 ), has been reported as a high-efficient OER catalyst recently. 19−21 This material is discovered in the 1970s, 22 with anomalously high thermopower, 23,24 superconductivity when intercalated with water, 25,26 unexpected metal−insulator transition, and its NFL states. 27,28 The lattice is composed of stacked layers of edge-sharing CoO 6 octahedra with inserted Na ions, where the charge carriers are confined in unusually narrow spaces, 25 2 .…”