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

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 O _2- electrocatalyst. The coordination of Co ²⁺ with the in situ generated ligands imidazole and carbonate results in ultrafine cobalt carbonate (CoCO ₃ )-involved cobalt-based zeolitic imidazole framework (CoCO ₃ /Co-ZIF). Owing to the presence of ultrafine CoCO ₃ , carbonization of CoCO ₃ /Co-ZIF at 800 °C under N ₂ atmosphere endows the pyrolysis product with a special skeleton of carbon nanotube (CNT)-tipped end CoO _x , multivalent CoO _x wrapped in graphitic carbon layers. Thus, the resulting CoO _x /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 IrO ₂ (1.62 V).