Selective Growth of a Discontinuous Subnanometer Pd Film on Carbon Defects for Li-O₂ Batteries

A high charge overpotential and poor cycle stability are the limiting factors in lithium-oxygen (Li-O₂) batteries, causing poor round-trip efficiency and cell failure. Many types of electrocatalysts have been explored to facilitate the oxygen evolution reaction (OER). However, even with the application of catalysts, it is still difficult to achieve stable operation as the carbon electrode (especially the defects) easily undergoes side reactions. To achieve high stability and round-trip efficiency, the rational design of OER catalysts and stable carbon electrodes are required. Herein, we employ a wet impregnation chemistry method to form a thin layer of palladium nanoparticles on the surface of carbon, which largely suppresses the side reaction through a selective coating on the carbon defect sites. Simultaneously, the Pd films serve as an electrocatalyst enabling the OER reaction with a very low overpotential. This rational design improves overall cell efficiency and extends the cycle life of the lithium-oxygen battery.