Improved lithium oxygen battery performance by addition of palladium nanoparticles on manganese oxide nanorod catalysts

The need for an alternative electrocatalyst to replace Pt-based noble materials is a major concern of the Li-air battery technology. In this work, alpha-MnO2 nanorods are synthesized by a simple hydrothermal technique and are modified with palladium (Pd) nanoparticles to form Pd-deposited alpha-MnO2 (Pd/alpha-MnO2) nanostructures. The physical characteristics of the thus prepared materials are analyzed by X-ray diffraction (XRD), SEM, and Brunauer-Emmett-Teller (BET) techniques. These analyses confirmed the successful synthesis of 8 similar to 10-nm-sized Pd nanoparticles deposited on 82 similar to 85-nm-sized alpha-MnO2 nanorods. The catalytic activities of the synthesized Pd/alpha-MnO2 nanostructure for oxygen reduction reaction and evolution reaction were studied by measuring linear sweeping voltammograms in aqueous solution. The as-prepared material exhibited high electrocatalytic activities which were comparable to that of the commercial Pt/C catalysts. The Pd/alpha-MnO2 nanostructures were then examined as a bifunctional electrocatalyst in the air cathode of Li-air batteries in non-aqueous media. The Li-air batteries fabricated with the Pd/alpha-MnO2 catalyst deliver a high discharge capacity with low overpotential compared to the other batteries without Pd deposition or any catalyst.