STRUCTURAL AND COMPOSITIONAL EFFECTS OF CELLULOSE NANOFIBER–GRAPHENE/BI₂TE₃ NANOCOMPOSITE FILMS FABRICATED BY ELECTRODEPOSITION

Abstract

Cellulose nanofiber (CNF) is a naturally derived nanomaterial known for its low thermal conductivity, making it an eco-friendly candidate for thermoelectric applications. This study explores the development of a CNF–graphene/Bi₂Te₃ nanocomposite thermoelectric material fabricated via electrodeposition using a three-electrode potentiostat setup. Electrolyte solutions containing nitric acid, bismuth-telluride ions, graphene, and varying CNF concentrations (0.5–2.0 g/L) were prepared to investigate CNF incorporation. The resulting films exhibited uniform distribution of CNF and graphene, with CNF content reaching up to 7.17 wt%. The Bi/Te atomic ratio remained stable (within 3.0 % of the stoichiometric Bi₂Te₃ phase), and the average grain size was reduced by ~35 % compared to pristine Bi₂Te₃ , enhancing phonon scattering and electron mobility. X-ray diffraction (XRD) confirmed the rhombohedral Bi₂Te₃ (R3-m) structure with characteristic (1010), (015), and (110) peaks. No CNF or graphene peaks were detected, indicating successful incorporation without the formation of separate crystalline phases. Increasing CNF content reduced and broadened the (1010) peak, with crystallite size decreasing from 32.2 nm to 21.3 nm (CNF–III). A slight shift toward higher 2θ in CNF–III suggests interfacial strain and hybrid structural interactions. These structural modifications—grain refinement, disrupted long-range crystallinity, and interfacial effects—are expected to enhance thermoelectric performance by reducing lattice thermal conductivity and improving charge transport. The CNF–graphene/Bi₂Te₃ hybrid film thus demonstrates strong potential for next-generation thermoelectric materials.