Determining the Active Surface Area for Various Platinum Electrodes

Various methods, i.e., the adsorption/stripping of adsorbed probe species, such as hydrogen (H), copper (Cu), and carbon monoxide (CO), oxygen and hydroxide (O/OH), potentiostatic CO/H displacement as well as double layer capacitance are exploited to evaluate the electrochemically active surface areas (ECAs) of platinum (Pt) foils, chemically deposited Pt thin film, and carbon-supported Pt nanoparticle electrodes. For the relatively smooth Pt electrodes (roughness factor < 3), the measurements from the stripping of H, Cu, and CO adlayers and CO/H displacement at 0.08 V (vs. RHE) give similar ECAs. With the increase of the surface roughness, it was found that the ECAs deduced from the different methods have the order of CO/H displacement less than the stripping of under potential deposition (UPD) Cu monolayer less than the stripping of the UPD-H adlayer. Possible origins for the discrepancies as well as the applicability of all the above-mentioned methods for determining ECAs of various Pt electrodes are discussed, and the UPD-Cu method is found to be the most appropriate technique for the determination of ECAs of Pt electrodes with high roughness factors or composed of nanoparticles with high dispersion.