Construction of high–loading 3D Co N C catalyst for oxygen reduction reaction in Zn–air batteries

The development of single atom catalysts is considered as a hotspot in the field of electrocatalysis. As the representative of single atom catalysts, metal and nitrogen co-doped carbon (M-N-C) attracts worldwide attentions due to its great potential in the application of oxygen reduction reaction (ORR). However, the actual preparation of M-N-C still confronts with tedious procedure, harsh condition and relatively low loading of single metal atom. In this work, we successfully prepare high-loading 3D Co-N-C architecture by a facile oxidation polymerization followed by pyrolysis process employing 3D nitrogen-doped graphene hydrogel (NGH) and pyrrole (PY) as the reaction precursors. Benefitting from the individual advantages of 3D NGH and PY, the resultant 3D Co-N-C possesses unique 3D architecture, high-loading single Co atom (2.74 wt%), large specific surface area and enriched mesopores, which benefit the exposure of sufficient catalytic sites and facilitate electrons transfer and ions transport, thus generating much enhanced ORR performance. When used as the cathode catalyst for zinc-air batteries (ZABs), it shows comparable performance with commercial Pt/C catalyst. Clearly, our finding offers a good guidance on the design and synthesis of advanced high-loading single atom catalysts.