Synthesis of Porous Carbon‐coated Cobalt Catalyst through Pyrolyzing Metal–Organic Framework and their Bifunctional OER/ORR Catalytic Activity for Zn‐Air Rechargeable Batteries
Yunseung Kuk, Sheraz Ahmed, Ho‐Jung Sun, Joongpyo Shim, Gyungse Park
Abstract
A metal–organic framework (MOF) was synthesized using 4,4′‐stilbenedicarboxylic acid (H 2 SDA) in dimethylformamide (DMF). Carbon‐coated Co (C@Co) catalysts were prepared by the direct calcination of Co 3 (SDA) 3 (DMF) 2 MOF crystals at various temperatures. The highest surface area of the C@Co catalyst is obtained at 600 °C which can further be increased by the ball mill operation. The X‐ray photon spectroscopy and X‐ray diffraction analysis proved the formation of metallic Co in the carbon matrix at temperatures over 500 °C, while Co 3 O 4 formation was observed at 500 °C. Furthermore, the graphitic properties of the Co particles were analyzed by Raman spectroscopy. The durability of the carbon‐coated Co catalysts derived from MOFs (C@Co catalysts) was analyzed by the cycle test (charge/discharge at 20 mA/cm 2 per 2 h) and was retained over 350 h. These catalysts showed remarkable stability for both ORR (oxygen reduction reaction) and OER (oxygen evolution reaction), comparable to that of Co 3 O 4 and Co metal powder in alkaline solution.