Insights into the origin of the enhanced electrical conductivity of Pd-Sb2O3 nanoparticles: A combined experimental and theoretical study

Supported metal nanocrystallites play a paramount role in catalysis, electrocatalysis, and gas sensing, among other fields. Although the majority of studies are focused on the modification of the composition, size and morphology of the active metallic phase to meet specific needs, the influence of the properties of the support on the overall behavior of such materials is often neglected. In a previous publication, we described for the first time the use of antimony trioxide (Sb2O3) as a new support material for Pd nanoparticles for the electrochemical oxidation of ethanol in alkaline media. Despite its high catalytic activity, information for the intrinsic fundamental properties of Pd-Sb2O3, such as the electrical conductivity and presence of defects, is still lacking. In this work, we combined both experimental techniques and theoretical simulations to gain further knowledge into some relevant physicochemical properties of the Pd-Sb2O3 system. An increase in electrical conductivity of 1000x is found in the Sb2O3 phase after the deposition of a small amount (4.9% weight) of Pd, which cannot be explained by the metallic phase; rather, oxygen vacancies in the Sb2O3 (as indicated by photoluminescence experiments) are likely the origin of such behavior. Theoretical calculations performed by density functional theory show that oxygen vacancies not only lead to distortion in chemical bonds but also change the overall reactivity of the system, corroborating X-ray photoelectron spectroscopy and electrochemical experiments.