Cobalt Diselenide Nanorods Grafted on Graphitic Carbon Nitride: A Synergistic Catalyst for Oxygen Reactions in Rechargeable Li−O2 Batteries

Abstract CoSe 2 nanorods are prepared through a hydrothermal approach and characterized by using various techniques to examine crystallinity, crystallite size, morphology, and defects present within. CoSe 2 is grafted on graphitic carbon nitride (g‐C 3 N 4 ) for oxygen reactions in a non‐aqueous medium. Li−O 2 batteries are assembled in di ‐methyl sulfoxide (DMSO) and investigated for charge‐discharge cycles at various current densities. The Li−O 2 battery with CoSe 2 @g‐C 3 N 4 delivers a discharge capacity of 2158 mAh g −1 at a current density of 0.1 mA cm −2 . The charging potential of the Li−O 2 battery is reduced by 280 mV in a combination of CoSe 2 and g‐C 3 N 4 . Electrochemical impedance spectroscopy of the Li−O 2 battery shows that the charge‐transfer resistance of the CoSe 2 catalyst is reduced from 311 to 181 Ω by adding g‐C 3 N 4 . Tetra‐ethylene glycol dimethyl ether is also used as the electrolyte to ensure better performance in terms of the stability of the cell in comparison to the DMSO electrolyte. Upon illumination of solar light, without any redox mediator, the overpotential of the charging step can be reduced. Under solar light illumination, the charging potential plateau shows a reduction of 330 and 170 mV in CoSe 2 and CoSe 2 @g‐C 3 N 4 samples, respectively.