Cobalt diselenide nanorods grafted on graphitic carbon nitride: a synergistic catalyst for oxygen reactions in rechargeable Li-O₂ battery

CoSe₂ nanorods are prepared via hydrothermal approach and characterized by using various techniques to examine crystallinity, crystallite size, morphology, and defects present within. CoSe₂ is grafted on graphitic carbon nitride (g-C₃N₄) for oxygen reactions in a non-aqueous medium. Li-O₂ batteries are assembled in dimethyl sulfoxide (DMSO) and investigated for charge-discharge cycles at various current densities. Li-O₂ battery with CoSe₂@g-C₃N₄ delivers 2158 mAh g⁻¹ discharge capacity at 0.1 mA cm⁻² current density. The charging potential of the Li-O₂ battery is reduced by 280 mV in a combination of CoSe₂ and g-C₃N₄. Electrochemical impedance spectroscopy (EIS) of the Li-O₂ battery shows that charge transfer resistance of CoSe₂ catalyst is reduced from 311 Ω to 181 Ω by adding g-C₃N₄. Tetra-ethylene glycol dimethyl ether also used as electrolyte to ensure better performing in terms of stability of the cell in comparison to DMSO electrolyte. Upon illumination of solar light without any redox mediator, the overpotential of charging step can be reduced. Under solar light illumination, the charging potential plateau shows a reduction of 330 and 170 mV in CoSe₂ and CoSe₂@g-C₃N₄ samples, respectively.