N-doped carbon-based single-atom catalysts (NC-SACs) are widely researched in various electrochemi-cal reactions due to high metal atom utilization and catalytic activity.The catalytic activity of NC-SACs originates from the coordinating structure between single metal site (M) and the doped nitrogen (N) in carbon matrix by forming M-Nx-C structure (1≤ x≤ 4).The M-N4-C structure is widely considered to be the most stable and effective catalytic site.However,there is no in-depth research for the “x” modula-tion in Pt-Nx-C structure and the corresponding catalytic properties.Herein,atomically dispersed Pt on N-doped carbon (Pt-NC) with Pt-Nx-C structure (1≤ x≤ 4),as a research model,is fabricated by a ZIF-8 template and applied to catalytic oxygen reduction.Different carbonization temperatures are used to control N loss,and then modulate the N coordination of Pt-Nx-C structure.The Pt-NC has the predictable low half-wave potential (E1/2) of 0.72 V vs RHE compared to the Pt/C 20％ of 0.81V due to low Pt content.Remarkably,the Pt-NC shows a high onset potential (1.10 V vs RHE,determined forj =-0.1 mAcm2) and a high current density of 5.2 mA cm-2,more positive and higher than that of Pt/C 20％ (0.96 V) and 4.9 mA cm-2,respectively.As the structural characterization and DFT simulation confirmed,the reducing Pt-N coordination number induces low valence of Pt atoms and low free energy of oxygen reduction,which is responsible for the improved catalytic activity.Furthermore,the Pt-NC shows high mass activity (172 times higher than that of Pt/C 20g),better stability and methanol crossover resistance.