Electrocatalytic trends on IB group metals: The oxygen reduction reaction

The rotating ring disk method (RRDE) is applied to investigate the oxygen reduction reaction (ORR) on Cu(111), Ag(111) and Au(111) single crystal surfaces in alkaline and acidic media. Independently of the pH of solution, we found that at low overpotentials the order of activity increases from Cu(111) to Ag(111) to An(111). At high overpotentials, however, Cu(111) and Ag(1 11) are much more active than An(111). An interpretation of the variation in activity is presented based on the premise that the rate of the ORR is controlled by two factors: a chemical-dependent part, Delta G(theta)(*) = Delta G(0)(*) + gamma Delta G(Theta)(0) Theta(ad), and the pre-exponential part which is determined by the adsorption of spectator species (Theta(ad)) and the availablitiy of bare metal sites, i.e., the (1- Theta (ad)) term.