Real surface area measurements of Pt3Co/C catalysts

An error analysis for real surface area (Am) measurements of Pt3Co/C catalysts is presented. The real surface area was measured by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), desorption of underpotential deposited hydrogen (Hupd) and CO-stripping voltammetry. All measurements were carried out after an electrochemical activation by cyclic voltammetry in perchloric acid. The real surface area decreases in the sequence Am(XRD) ∼ Am(HRTEM) > Am(CO-stripping) ∼ Am(Hupd). HRTEM provides the highest reliability of the investigated methods. The electrochemical methods are questionable for Pt3Co/C catalysts. They yield surface areas which are 23–30% lower than determined by HRTEM. The surface coverage of adsorbed H and CO is apparently lower on Pt3Co compared to Pt nanoparticles. Cyclic voltammetry of Pt3Co/C in alkaline electrolyte suggests that the surface of acid leached Pt3Co nanoparticles consists of pure Pt.