Validating Electrochemical Active Surface Area Determination of Nanostructured Electrodes: Surface Oxide Reduction on AuPd Nanoparticles

Abstract

Accurate normalization of electrochemical active surface area (ECSA) of nanostructured catalysts and nanoparticles is of utmost importance for catalyst activity determination and comparability. Au x Pd y nanoparticles are a highly interesting example, as electrocatalysts for selective oxygen reduction reaction and alcohol oxidation. Most techniques used today for ECSA determination lack accurate validation for nanostructured electrodes and instead rely on reference values determined for macroelectrodes. This includes ECSA determination for Au x Pd y nanoparticles, most commonly done by potentiodynamic surface oxide reduction. Here we suggest a versatile approach to validate different ECSA determination techniques for nanoparticle-modified or nanostructured electrodes, using surface oxide reduction of Au x Pd y as an illustrative example. Combining this with volume determination by anodic stripping, we electrochemically estimate the NP diameter, which serves as an indication of the accuracy of the obtained ECSA values. Showcasing this for different nanoparticle compositions, we provide experimental conditions for determining Au x Pd y nanoparticle ECSA using surface oxide reduction and compare those to parameters reported for macroelectrodes. The approach we introduce herein can be readily applied to a number of different alloy systems, thus, providing a widely applicable approach to determine electrochemical surface areas and validate the transferability of existing macroelectrode characterization techniques to nanostructured or nanoparticle-modified electrodes.