Controllable morphology of Pd-loaded potassium tantalates with high catalytic performance for ethylene glycol electrooxidation

Abstract In this work, potassium tantalates (KxTaxO3x, x=1 or 2) with different crystal structures and morphologies are synthesized with a one-step hydrothermal method. The concentration of the KOH reactant played a crucial role in controlling the morphology of KxTaxO3x. When the concentration of KOH is low, an octahedral pyrochlore (K2Ta2O6) is obtained. In contrast, the cubic perovskite (KTaO3) is obtained at high KOH concentrations. Pd nanoparticles loaded onto K2Ta2O6 and KTaO3 (Pd/K2Ta2O6, Pd/KTaO3) electrocatalysts are then prepared with reflux reduction in ethanol. X-ray photoelectron spectroscopy results imply that the loading palladium is in the main Pd° form. The electrocatalytic activity of the Pd/K2Ta2O6 and Pd/KTaO3 electrocatalysts is investigated using cyclic voltammetry (CV) toward ethylene glycol (EG) oxidation in an alkaline medium. The CV results show that Pd/K2Ta2O6 and Pd/KTaO3 electrocatalysts modified glassy carbon electrodes have excellent catalytic activity for EG electrooxidation in an alkaline medium, superior to that of commercial Pd/C (10%). The enhancement of their electrocatalytic activity was owing to the synergistic reaction between Pd and KxTaxO3x. In addition, the electronic structure of the Pd/K2Ta2O6 and Pd/KTaO3 electrocatalysts was assessed using density functional theory. The calculation results indicated that electron transfer occurred in the complex region of Pd and KxTaxO3x.