CoO@Co and N-doped mesoporous carbon composites derived from ionic liquids as cathode catalysts for rechargeable lithium–oxygen batteries†
The catalytic activity of a cathode material plays a vital role in determining the electrochemical performance of Li–O2 batteries. Herein, N-doped mesoporous carbon-supported CoO@Co nanoparticles are prepared in situ using the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrachlorocobalt ([BMIm]2[CoCl4]) as the precursor with silica as the hard template. The material was characterized by TGA, BET, XRD, TEM, XPS, and H2-TPR. After exposure to air, the species on the surface of the Co is CoO, as verified by XPS. The pore size is about 2 nm, and the CoO@Co nanoparticles were irregularly shaped and sized in the range of 20–300 nm, which may have been due to the aggregation of ultrafine nanoparticles. The existence of an interaction between the CoO@Co nanoparticles and the N-doped support is confirmed by XPS and H2-TPR. The catalyst shows superior activity for oxygen evolution reaction (OER) manifested in its lower charge potential (3.75 V at the current density of 100 mA g−1). Enhanced performances in coulombic efficiency, rate capability, and cycling stability (55 cycles) are also realized. Finally, these improvements, with the exception of the catalytic activity of CoO, may benefit from the interaction between the carbon supporter and the CoO@Co nanoparticles.