MOF-Derived Nanoporous Carbon As an Efficient Bifunctional Oxygen Electrocatalyst for Erzabs

Abstract

Zinc-air batteries are cost-effective batteries that possess a high energy density (1086 Wh Kg -1 ), compared to other conventional battery systems. In order to improve the electrochemical performance of electrically rechargeable zinc-air batteries (ERZABs), an effective bifunctional oxygen electrocatalyst is required. Hence, the development of non-noble metal bifunctional catalysts for ORR and OER is of prime importance. The transition metal-based catalysts have increasing demand since they are promising alternatives, in terms of cost and durability, to noble metal catalysts. Metal-organic frameworks (MOF) based catalysts show high catalytic activity due to adjustable pore size, ultra-high surface area, and structural designability [1] .Increasing porosity can augment the catalytic activity by increasing the surface area, thereby enhancing the ORR kinetics. In the present work, a CFZ-NPC (CoFeZn-MOF derived nanoporous carbon) was synthesized via hydrothermal method and investigated as a bifunctional catalyst for rechargeable zinc-air batteries [2] . The catalyst shows a high electrochemical activity towards oxygen reduction reaction with a half-wave potential of 830 mV vs. RHE and a comparable oxygen evolution activity (overpotential of 379 mV vs. RHE at 10 mA cm -2 ) with IrO 2 (Over potential of 377 mV at 10 mA cm -2 ). The binder-free CFZ-NPC air electrode when applied into a Zinc-air battery system, delivers a low charge-discharge potential gap of 862 mV at 5 mA cm -2 . Interestingly, the catalyst possesses an excellent electrochemical performance in the electrically rechargeable Zn-air battery over 1000 cycles at selected DOD for 157 h with a specific capacity of 890 mAh g (Zn) -1 without much efficiency drop. Financial support from Department of Science and Technology, Govt. of India under research grant number DST/TMD/MECSP/2K17/20 is gratefully acknowledged References; [1] Ren, Shuangshuang et al. 2020. “Bifunctional Electrocatalysts for Zn-Air Batteries: Recent Developments and Future Perspectives.” Journal of Materials Chemistry A 8(13): 6144–82. [2] Tang, Jing et al. 2016. “Bimetallic Metal-Organic Frameworks for Controlled Catalytic Graphitization of Nano porous Carbons.” Nature Publishing Group (April): 1-8.