β-FeOOH nanorod bundles with highly enhanced round-trip efficiency and extremely low overpotential for lithium-air batteries.

β-FeOOH nanorod (NR) catalysts prepared by ultrasonic-irradiated chemical synthesis enabled lithium-air cells to have high round-trip efficiency and extremely low overpotential as well as an outstanding rate capability. Good catalytic activities of the β-FeOOH NR bundle could be ascribed to its crystal structure, which consists of 2 × 2 tunnels formed by edge- and corner-sharing Fe(O,OH)6 octahedra as well as to its one-dimensional morphology, which makes the configured electrode highly porous, indicating that the -OOH-based catalyst can be a good substitute for oxide-base catalysts in lithium-air batteries. The ultrasonic-irradiated chemical synthesis suggested here may be a good solution to optimize the morphology of catalyst materials for maximum catalytic activity.