Suppressing Ion Transfer Enables Versatile Measurements of Electrochemical Surface Area for Intrinsic Activity Comparisons.

Correlating the current/voltage response of an electrode to the intrinsic properties of the active material requires knowledge of the electrochemically active surface area (ECSA), a parameter that is often unknown and overlooked, particularly for highly nanostructured electrodes. Here we demonstrate the power of nonaqueous electrochemical double layer capacitance (DLC) to provide reasonable estimates of the ECSA across 17 diverse materials spanning metals, conductive oxides, and chalcogenides. Whereas data recorded in aqueous electrolytes generate a wide range of areal specific capacitance values (7-63 μF/real cm2), nearly all materials examined display an areal specific capacitance of 11 ± 5 μF/real cm2 when measured in weakly coordinating KPF6/MeCN electrolytes. By minimizing ion transfer reactions that convolute accurate DLC measurements, we establish a robust methodology for quantifying ECSA, enabling more accurate structure-function correlations.