Rotating ring disk electrode studies show that the polarization curves for reduction on platinum in buffered are shifted cathodically relative to those in buffered in the pH range of 8–10, presumably due to chloride ion adsorption. Increased currents at the ring also provide evidence of Cl−‐specific adsorption in this pH range. The calculated rate constant, , for oxygen reduction in weakly alkaline, borate‐buffered solutions shows the inhibiting effect of Cl− ion. Triangular sweep cyclic voltammetry studies provide supporting evidence of chloride adsorption on platinum in the pH range of 8–12.