Structure-Dependent Electrical Double-Layer Capacitances of the Basal Plane Pd(<i>hkl</i>) Electrodes in HClO₄

Abstract

Electrical double-layer capacitance (CDL) measurements are among the key experiments in physical electrochemistry aimed to understand the properties of electrified solid/liquid interfaces. CDL serves as a critical parameter for developing physical models of electrochemical interfaces. Palladium (Pd) electrodes are among the most widely used functional materials in many applications, including (electro)catalysis. In this work, we report on double-layer capacitances of the basal plane Pd(111), Pd(100), and Pd(110) electrodes in aqueous HClO4 electrolytes measured using electrochemical impedance spectroscopy. Importantly, we find that the CDL values estimated at the minima of the capacitance vs electrode potential curves can be correlated with the density-functional-theory (DFT)-calculated adsorption energies for water molecules and the coordination of electrode surface atoms. Our results thus suggest that it might be possible to find simple descriptors of the electrical double layer (EDL) analogous to those used for functional electrode materials. Taken together, such descriptors could be employed for efficient high-throughput screening of various electrode/electrolyte interfaces, such as in supercapacitor and electrocatalytic systems.