N-Doped Defective Carbon Layer Encapsulated W₂C as a Multifunctional Cathode Catalyst for High Performance Li-O₂ Battery

The sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) restricts the practical application of Li-O₂ batteries. The design and facile synthesis of cathode catalysts with high activity on both ORR and OER are desired. In this study, an ultrathin N-doped defective carbon layer-encapsulated W₂C hybrid (W₂C@NC) which has been successfully synthesized through a facile in-situ pyrolysis and reduction of WO₃@g-C₃N₄ shows a high activity on ORR, OER and even the decomposition of the undesired Li₂CO₃ as a multifunctional cathode catalyst for Li-O₂ batteries. The cells catalyzed by W₂C@NC show a much higher initial capacity of 10976 mAh g⁻¹, lower overpotential and longer cycle life, which can be largely attributed to the synergistic effect of W₂C nanoparticles and the ultrathin defective N-doped carbon layers. The unique architecture not only accelerates the electron and Li⁺ conduction but also provides more active sites, which lead to the large enhancement of the electrocatalytic performance. In addition to the high activity on both ORR and OER, W₂C@NC also shows a high catalytic function on the decomposition of the undesired side product of Li₂CO₃. This study offers some new insights into the design and synthesis of novel high performance cathode catalyst for Li-O₂ battery.