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The oxygen reduction reaction (ORR) is an important process in many fields, including energy conversion (fuel cells, metal–air batteries),[1] corrosion,[2] and biosensing.[3] For fuel cells, the cathodic oxygen reduction is a major factor limiting their performance.[4] The ORR can proceed either through a four-electron process to directly combine oxygen with electrons and protons into water as the end product, or a less efficient two-step, two-electron pathway involving the formation of hydroperoxide ions as intermediate.[4] Oxygen reduction also occurs, albeit too slowly to be of any practical significance, in the absence of an ORR catalyst on the cathode. Platinum nanoparticles have long been regarded as the best catalyst for the ORR and are still commonly used in fuel cells due to their relatively low overpotential and high current density with respect to other commercial catalysts.[5] However, the ORR kinetics on the Pt …