Mechanism of Oxygen Reduction Reaction on Transition Metal–Nitrogen–Carbon Catalysts: Establishing the Role of Nitrogen-containing Active Sites

Using molecular probes that have unique spectral signatures and have strong selective binding to the potential active sites allows elucidating the mechanism of different reactions. The mechanism of oxygen reduction reaction in metal–nitrogen–carbon (MNC) catalysts has been studied by using a bisphosphonate complexing agent, which improves the selectivity of ORR by blocking the protonated and hydrogenated nitrogen that are catalyzing the partial reduction of oxygen to hydrogen peroxide. A combination of theoretical, electrochemical and spectroscopic with focus on near-ambient pressure X-ray photoelectron spectroscopy is used to directly probe the competition between binding of oxygen and molecular probe to the surface of MNC catalyst and to identify the role of different types of nitrogen in the mechanism of ORR.