On the nature of adsorbed species on platinum single-crystal electrodes

The dependence of voltammetric currents on multiple parameters (concentration, pH, temperature, etc) has become a primary source of information in interfacial studies of noble metal electrodes. Peak potential, charge, and width are intimately related to surface structure and reactivity. However, this interpretation usually neglects the complexity of the redox processes involved. For the so-called hydrogen adsorption region in platinum, anion competitive adsorption plays an important role that is usually overlooked. While charge displacement already demonstrated decades ago the existence of anion adsorption contributions, only recently a combination of several surface-sensitive techniques has proven unambiguously the presence of OH adsorbed on step sites at potentials much lower than usually considered. This information must not be neglected when analyzing the properties of complex catalysts, such as those composed of nanoparticles, since it is of great importance for understanding its overall reactivity, comparing with computational results, and performing coulometric analysis.