Non-precious metal-nitrogen-carbon (MNC) electrocatalysts have gained tremendous attention as promising electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the most applicable strategies for the synthesis of MNC materials heavily rely on pyrolysis treatment, which may easily lead to metal aggregation and subsequent degradation of catalytic performance. Herein, we developed a pyrolysis-free strategy for preparing MNC materials, which was demonstrated by achieving ultrathin cobalt-nitrogen-carbon (CoNC) layer with dense atomically dispersed cobalt sites depositing on graphene oxide (GO) via simple treatment of Co salt and GO in formamide. The formamide-derived CoNC layer deposited on GO (termed as f-CoNC/GO) could be controlled in 1~2 nm thick. Remarkably, the f-CoNC/GO composite without pyrolysis exhibited excellent bifunctional performance toward ORR and OER, which was attributed to the dense atomically dispersed Co-Nx sites and improved conductivity by GO substrate. Furthermore, the f-CoNC/GO-assembled rechargeable Zn-air battery showed highly efficient and stable performance, demonstrating our pyrolysis-free method to be straightforward, cost-effective, and feasible for the scalable production of MNC electrocatalysts.