Oxygen reduction on single crystal platinum electrodes in phosphoric acid solutions

Oxygen reduction reaction has been studied on Pt low index planes in 0.1 M and 85% H3PO4 using hanging meniscus rotating disc electrode technique. The first-order kinetics of O2 reduction reaction was found for all three surfaces in a four-electron process with the first electron transfer rate determining in both 0.1 M and 85% H2PO4 solutions. Catalytic activity for O2 reduction follows the sequence Pt (110)>>Pt (100)>>Pt (111). Structural dependence is predominantly determined by the adsorption of phosphoric acid anions, which is strongly structure-dependent on Pt surfaces.