Galvanically Displaced Ultralong Pb<sub><i>x</i></sub>Se<sub><i>y</i></sub>Ni<sub><i>z</i></sub> Hollow Nanofibers with High Thermopower

A cost-effective process that combines electrospinning and a galvanic displacement reaction was utilized to synthesize ultralong hollow Pb<sub><i>x</i></sub>Se<sub><i>y</i></sub>Ni<sub><i>z</i></sub> nanofibers with controlled dimensions, morphology, composition, and crystal structure. Ni nanofibers were electrospun with an average diameter of 150 nm and were used as the sacrificial material for the galvanic displacement reaction. The composition and morphology of the Pb<sub><i>x</i></sub>Se<sub><i>y</i></sub>Ni<sub><i>z</i></sub> nanofibers were controlled during the reaction by tuning the concentration of HSeO<sub>2</sub><sup>+</sup> in the electrolytes. Hollow Pb<sub><i>x</i></sub>Se<sub><i>y</i></sub>Ni<sub><i>z</i></sub> nanofibers with smooth surfaces were obtained from the low-concentration HSeO<sub>2</sub><sup>+</sup> solution (i.e., 0.01 and 0.05 mM), but the hollow nanofibers synthesized from the high-concentration HSeO<sub>2</sub><sup>+</sup> solution (i.e., 1 mM) have rough outer surfaces with nanocrystal protrusions. The Pb content of the nanofibers’ composition was varied from 3 to 42% by adjusting the HSeO<sub>2</sub><sup>+</sup> concentration. The thermoelectric properties of the nanofiber mats were characterized, and the highest Seebeck coefficient of approximately 449 μV/K at 300 K was found for the Pb<sub>37</sub>Se<sub>59</sub>Ni<sub>4</sub> nanofiber mat.