Developing printable thermoelectric materials based on graphene nanoplatelet/ethyl cellulose nanocomposites

Abstract

Thermoelectric (TE) materials have drawn a lot of attention as a promising technology to harvest waste heat and convert it into electrical energy. However, the toxicity and expense of inorganic TE materials along with high-temperature fabrication processes have limited their application. Additionally, the reduction of raw material resources, such as metals and petroleum is another limiting factor. Hence, developing low-cost, stable, and easily-created TE materials from renewable resources is attracting more and more interest for a wide range of applications including the internet of things and self-powered sensors. Herein, an efficacious processing strategy to fabricate printable TE materials has been developed with Ethyl cellulose (EC), a non-conducting polymer, as the polymer matrix and with Graphene nanoplatelets (GNPs) as fillers. EC, one of the cellulose’s derivatives, has been widely used as a binder in the printing pastes. The conductive pastes with different filler contents have been fabricated. The weight ratio of GNPs and EC were ranged from 0.2 to 0.7. These conductive pastes have been deposited by blade coating on glass substrates. The electrical conductivity of the composites has increased polynomially as the filler content increased, whereas the Seebeck coefficient did not change significantly with the increased electrical conductivity. The highest electrical conductivity at room temperature (355.4 S m−1) was obtained for the ratio of 0.7. This ratio also had the maximum power factor value. Moreover, a 3D structure form (cylindrical pellet) from the highest conductive paste was also fabricated. The proposed technique demonstrates an industrially feasible approach to fabricate different geometries and structures for organic TE modules. So, this approach could provide a good reference for the production of high efficiency, low-temperature, lightweight, low-cost, TE materials.

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

“…The electrical conductivity has an increasing trend with GNPs content. This trend can be explained by the formation of a GNPs network inside the polymer 9 . Moreover, the Seebeck coefficient increases, as the filler content increases.…”

“…So, thick PEDOT:PSS layers are advantageous in TE applications 7,8 . Although there are some reports of thick film or bulk form of organic TE materials 9 , it is still challenging to develop a thick or bulky high-performance PEDOT:PSS material [10][11][12][13] . The challenge relies on the limited control of their morphology and structure 8 .…”

“…The electrical properties of GNPs/paper samples without the PEDOT:PSS layer as a function of GNPs content are presented in Fig 4a . The electrical conductivity has an increasing trend with the increase of the filler content since the conductive filler network has begun to form between the diverse nanoflakes 9 . In particular, it improves from 3.4 mS/cm to 84.7 S/cm when the filler content increases from 4% to 50%, respectively.…”

Advances in carbon‐based thermoelectric materials for high‐performance, flexible thermoelectric devices

“…Studies on composites consisting of graphene and other conductive polymers such as polyvinyl acetate, polypyrrole, and polyvinylidene fluoride are still ongoing 122–125 . Recently, Mardi et al 120 reported GNPs/ethyl cellulose nanocomposites for TE. Ethyl cellulose is a nonconducting polymer that is a cheap, abundant, green, and biocompatible material.…”

“…Furthermore, the maximum output powers of 16.2 and 40.1 nW were generated from the pellets at temperature differences of 20.5 and 32.3 K, respectively. The authors have taken the first step of using easily processable, low‐cost, and sustainable polymers in TE materials for commercialization in the future 120 . The TE properties of carbon allotropes (CNT, graphene) that were discussed above are summarized in Figure 12.…”