At present, on average 60% of the total energy utilized in diverse industrial and processing activities dissipates as waste heat[1–3].The current goal of reducing carbon dioxide emissions and achieving carbon neutrality requires the adoption of clean, sustainable energy sources, coupled with enhancing energy conversion efficiency[4–6]. A notable portion, exceeding 50%, of heat dispersion in industrial settings emanates from low-grade sources. Reducing fossil fuel consumption and ameliorating the resultant environmental crisis can be facilitated by recovering low-grade heat [7–10]. Thermoelectric (TE) devices offer a viable avenue for recovering low-temperature waste heat by converting it into electrical energy through the Seebeck effect[11–15]. Due to their solid-state operation, along with high stability and durability thermoelectric technology presents opportunities for harnessing usable electricity from waste heat[16–18]. Also, it has the potential to mitigate the escalating energy demand and reduce the challenge of fossil fuel depletion. The efficacy of thermoelectric materials is commonly assessed using the dimensionless figure of merit zT, calculated as zT = S2σT/κ, where S denotes the Seebeck coefficient, σ is electrical conductivity, κ represents thermal conductivity (comprising electronic, lattice, and bipolar components), and T stands for absolute temperature[19–21].Consequently, an optimal thermoelectric material ideally possesses high electrical conductivity and a substantial Seebeck coefficient along with low thermal conductivity[22–24]. Conventional high-efficiency thermoelectric materials like Bi2Te3, GeTe, PbTe/Se, Cu2S/Se, and half Heusler exhibit peak zT values across distinct temperature spectra, primarily dueto variations in their band gaps[25–31]. Notably, the Bi2Te3 system stands out as the leading choice for thermoelectric applications owing to its superior thermoelectric characteristics, Particularly at room temperature[32–35]. Bismuth telluride (Bi2Te3), categorized as a narrow band gap semiconductor, exemplifies these characteristics with its relatively elevated electrical conductivity, significant Seebeck coefficient, and low thermal conductivity within the range of 300–500 K[36–39].
Recently, significant attention has been directed toward enhancing the figure of merit (zT) in Bi2Te3 through the utilization of nanoscale geometrical constraints in one, two, or three dimensions, or by tailoring the shape of nanoparticles[40–42]. This interest stems from both theoretical predictions and experimental findings, which suggest that nano structuring thermoelectric materials hold promise for achieving notable improvements in zT[43–48]. This improvement is attributed to the combination of a high density of states and enhanced phonon scattering which reduces lattice thermal conductivity in nanostructured systems. Despite extensive exploration into the synthesis and assembly of nanostructures of bismuth telluride, such as nanorods, nanowires, nanoparticles, and nanosheets, there is still a need for the development of novel nanostructures of bismuth telluride intermetallic compounds with precise control of their crystalline morphology through straightforward, rapid, and cost-effective methods.
Contemporary efforts are aimed at fabricating nanostructured thin films of Bi2Te3. A variety of techniques have been utilized in the synthesis process, including solvothermal, hydrothermal, pulsed laser deposition, thermal evaporation, and electrodeposition[49–53]. Of these techniques, electrodeposition holds promise for achieving uniform nanostructures of Bi2Te3 owing to its advantageous characteristics, such as synthesis at low temperature, eliminating of the need for a vacuum, high deposition rate, low cost, and the ability to control the composition, structure, and morphology of the synthesized material. This method facilitates precise control of growth rate by varying parameters such as electrolyte concentration, pH, and deposition potential. The potentiostatic approach within electrodeposition stands out for its simplicity and superior control over the rate of various possible electrochemical reactions[39, 40, 54–56].
To fine-tune the properties of Bi2Te3 films for enhancement in thermoelectric performance, the electrodeposition parameters must be optimized. Previous threads of the research reveal an optimized deposition voltage of -400 mV/SCE and an optimum pH of 0.5 for depositing Bi2Te3 films with high Seebeck coefficients and Power factors[57, 58]. Current research is performed to optimize theBi3+ ion concentration in the electrodeposition electrolyte for the best thermoelectric properties of Bi2Te3.The concentration of the Bi3+ ions has been varied from 2.5 mM to 15 mMin steps of 2.5 mM. X-ray diffraction, Phase analysis, EDAX, SEM images, and Cyclic Voltammetry curves of the films have been studied to confirm the deposition of Bi2Te3 with ideal structural, and morphological properties. While Four Probe analysis along with thermal conductivity have been studied for electrical, thermoelectric and thermoelectric properties. The thermoelectric properties of the deposited films indicate an optimum concentration range of Bi3+ for the said purpose.