Highly reactive N,N′-carbonyldiimidazole-tailored bifunctional electrocatalyst for oxygen reduction and oxygen evolution

Abstract

The rational design and synthesis of an efficient bielectrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) by tuning the chemical composition, structure and the catalytic sites of the hybrid materials is always of a great challenge. In this work, an innovative strategy based on the highly active N,N′-carbonyldiimidazole (CDI) is described to one-pot synthesis of a novel precursor for bifunctional O2-electrocatalyst. The coordination of Co2+ with the in situ generated ligands imidazole and carbonate results in ultrafine cobalt carbonate (CoCO3)-involved cobalt-based zeolitic imidazole framework (CoCO3/Co-ZIF). Owing to the presence of ultrafine CoCO3, carbonization of CoCO3/Co-ZIF at 800 °C under N2 atmosphere endows the pyrolysis product with a special skeleton of carbon nanotube (CNT)-tipped end CoOx, multivalent CoOx wrapped in graphitic carbon layers. Thus, the resulting CoOx/Co-N-C exhibits the enhanced and durable ORR/OER performance in alkaline media, due to the fast electron and mass transfers. For ORR, a large limiting current density of 4.59 mA cm−2 can be obtained by CoOx/Co-N-C, which is comparable to that of Pt/C. For OER, it only needs an over potential of 1.65 V to achieve a current density of 10 mA cm−2, merely 30 mV behind IrO2 (1.62 V).