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

3 years ago

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

Ru Shi Liu, Chaolun Liang, Wuzong Zhou, Wen Sheng Chang, Yao Chong Hu, Anirudha Jena, Tai Feng Hung, Surender Kumar, Ho Chang

CoSe2 nanorods are prepared through a 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 di-methyl sulfoxide (DMSO) and investigated for charge-discharge cycles at various current densities. The Li−O2 battery with CoSe2@g-C3N4 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−O2 battery is reduced by 280 mV in a combination of CoSe2 and g-C3N4. Electrochemical impedance spectroscopy of the Li−O2 battery shows that the charge-transfer resistance of the CoSe2 catalyst is reduced from 311 to 181 Ω by adding g-C3N4. 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 CoSe2 and CoSe2@g-C3N4 samples, respectively. Pore-fection: The composite of g-C3N4 with CoSe2 provides a new class of material as a bifunctional catalyst for oxygen reactions in Li−O2 batteries. A reduction of the overpotential can be ascribed to the synergistic catalysis by both components, as shown in the picture. The presence of g-C3N4 facilitates electron transfer, which can free-up clogged pores of the electrode material from oxygen reactions.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/celc.201700909