Synthesis of Tellurium Heterostructures by Galvanic Displacement Reaction of Zinc in Alkaline Baths

Tellurium (Te) nanostructures, including nanowires and branched nanorods, were synthesized by galvanic displacement reaction (GDR) of zinc foils in alkaline baths containing TeO32− ions. The dimension, morphology, and crystal structure of the Te nanostructures were controlled by varying the electrolyte composition, pH, and the reaction temperature. For examples, single crystalline Te nanowires were synthesized at low TeO32− concentrations (e.g., 2 mM), whereas 3-D branched nanorods were obtained at higher TeO32− concentrations (e.g., >10 mM) at a fixed pH of 13.1. The diameter of the branches was increased by increasing TeO32− concentration. Solution pH also effected the morphology of Te heterostructures where the pH range from 12.8 to 13.1 yielded branched nanorods whereas higher pH (i.e., 14.7) yielded nanowires at a fixed TeO32− concentration (i.e., 10 mM). Reaction temperature predominately effected on the dimension where the average diameter increased from 49 nm to 200 nm with increasing temperature from 4 °C to 50 °C. Various electrochemical analytical methods including open circuit potential (OCP), linear sweep voltammograms (LSVs) as well as linear potentiodynamic polarizations (LPs) were carried out to understand the underlying reaction mechanism. Based on these analysis, the formation of branched nanorods was attributed to secondary nucleation at the crystal imperfections.