Shape-Controlled Synthesis of Palladium Nanostructures from Flowers to Thorns: Electrocatalytic Oxidation of Ethanol

The study focuses on facile shape-controlled deposition of rose, splintery, chrysanthemum flower, and thorn-like structures of palladium on indium-tin-oxide substrates. The hierarchical variation in morphologies from roses to thorns is attributed to a rational choice of the applied potential. This study involved investigating the influence of the precursor concentration, nature of the electrolyte, and deposition time on the morphological patterns. The shape-dependent electrocatalytic performance of these structures for oxidation of ethanol is demonstrated using cyclic voltammetry and electrochemical impedance spectroscopy. The onset potential, active surface area, mass activity, and exchange current density are investigated, and the results indicate that the catalytic activity of thorn-like morphologies is superior to that of the other shapes. The structural growth mechanism of the thorns deduced via scanning electron microscopy reveals the progression from spheres to thorns via cotton wools. The directional growth patterns via transmission electron microscopy indicate that the nanospikes of each thorn exhibit growth with the main branch of the (200) plane and the side branches along the (111) direction.