Heterocarbon nanosheets incorporating iron phthalocyanine (FP-NCNs-SP) have been successfully synthesized by a facile one-pot solution plasma process at high repetition frequency. It was found that the Fe–N₄ catalytic active sites could be preserved on the FP-NCNs-SP without degradation. The FP-NCNs-SP also possessed large surface area, good conductivity and high degree of graphitization. Electrochemical evaluations demonstrated that NCNs-SP had excellent electrocatalytic activity and selectivity toward oxygen reduction reaction (ORR) in alkaline medium through a direct four-electron pathway. Although the significant improvement in ORR activity was clearly observed in acidic medium, it was much poorer than in alkaline medium. We believe that the results presented in this work will shed light on the advanced synthesis and design of ORR electrocatalysts at room temperature with an abundance of catalytically active sites and high ORR performance.