Glucose‐hexamethylenetetramine‐derived Co, N Co‐doped Carbon Nanoflowers with Encapsulated Co@Co₃O₄ as Efficient Bifunctional Oxygen Electrocatalyst for Zinc‐air Batteries

Abstract

Developing low-cost, eco-friendly, and efficient bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is an important issue for zinc-air batteries. In this study, HMT-Co/G-700 catalyst with nanoflower structure and Co, N co-doped carbon encapsulated Co@Co 3 O 4 nanoparticles are synthesized from D-glucose, hexamethylenetetramine (HMT), and Co-(NO 3 ) 2 . HMT is presented as the complex to uniformly disperse Co@Co 3 O 4 nanoparticles, dope nitrogen, and create the nanoflower structure. The nanoflower structure enhances high surface area to expose the active sites. The formation of Co 3 O 4 via mild oxidation of Co surface provides oxygen vacancies to adsorb O 2 . HMT-Co/G-700 catalyst exhibits excellent ORR electrocatalytic property, i. e. high onset potential (1.03 V), high half-wave potential (0.83 V), low Tafel slope (85.9 mV dec À 1 ), and superior OER activity. Especially, the HMT-Co/G-700 catalyst assembled rechargeable zinc-air battery present high-power density (111.0 mW cm À 2 ) and long cycle life at 10 mA cm À 2 (576 cycles).