Role Platinum Nanoparticles Play in the Kinetic Mechanism of Oxygen Reduction Reaction in Nonaqueous Solvents

Although lithium–oxygen batteries theoretically have high energy density, they are far from becoming viable and practical alternatives to current batteries because the oxygen reduction reaction (ORR) is slow, which limits the applicability of lithium–oxygen batteries, and these power sources require suitable catalysts for optimum performance. Understanding the chemical and electrochemical steps involved in the ORR mechanism is mandatory. This work investigates platinum nanoparticles (Pt-nps) dispersed in graphitized carbon as a positive electrode for lithium–air batteries, characterizes the materials by cyclic voltammetry and galvanostatic cycling, X-ray diffraction, and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and determines the kinetic constants for the reaction mechanism steps with the help of electrochemical impedance measurements and modeling. The electron transfer to oxygen molecules adsorbed onto Pt-nps is the rate-limiting step. Li2O2 is preferentially produced via the electrochemical pathway instead of the chemical disproportionation reaction, leading to a device with improved reversibility and enhanced energy density.