Europium (III) doped bismuth telluride decorated on carbon-based materials for enhancing thermoelectric performance

Abstract

Scalable synthetic approach for superior performance of thermoelectric (TE) materials is a crucial step for the TE technology progress. Herein, reduced graphene oxide (RGO), carbon nitride (g-C 3N4) and europium (Eu) are utilized as additives to bismuth telluride (Bi2Te3) matrix to prepare various novel nanocomposites (NCs): (RGO@Bi1.8Te3Eu0.2) and (RGO-g-C3N4@Bi1.8Te3Eu0.2) with an enhanced TE performance. The novel NCs were synthesized via solvothermal method, physiochemically characterized and consolidated into pellets of 1 mm thickness to measure their TE properties. The new additives potentially affected the physicochemical and TE properties of Bi2Te3. Nanostructured hexagonal nanoplatelets with 12.5 nm thickness were observed by scanning and transmission electron microscopy (SEM and TEM) of the synthesized Bi2Te3. This thickness shrinked to 5.7 and 5.2 nm upon the formation of (RGO@Bi1.8Te3Eu0.2) and (RGO-g-C3N4@Bi1.8Te3Eu0.2) NCs, respectively. Energy dispersive X-ray Spectroscopy (EDS) of NCs proved the existence of Bi, Te, C, Eu and N atoms. Raman and Fourier-transform infrared (FT-IR) spectra confirmed the NC formation that led to narrowing the energy band gap of Bi2Te3 as displayed by UV–Vis spectra. Brunauer–Emmett–Teller showed specific surface area expansion of Bi2Te3 from 6.78 to 19.00 and 16.75 m2g-1 of (RGO@Bi1.8Te3Eu0.2) and (RGO-g-C3N4@Bi1.8Te3Eu0.2) NCs, respectively. The electrical conductivity of Bi2Te3 rose by 56 and 69 times, whereas its thermal conductivity significantly dropped by 1.6 and 1.7 times upon (RGO@Bi1.8Te3Eu0.2) and (RGO-g-C3N4@Bi1.8Te3Eu0.2) NCs formation. Owing to extra channels of carrier transfer and phonon scattering induced by NCs heterointerfaces. Novel combination of carbon-based materials and Eu with Bi2Te3 matrix boosts its TE performance resulting in a worthy candidate for power generation applications at room-temperature.