fig4

Figure 4. (A) ORR LSV curves of COP_MCT-Co-900, COP_MCP-Co-900 and COP_MCZ-Co-900; (B) LSV of COP_MCT-Co-900 at different rotating rates; (C) The corresponding K-L plots at various potentials, respectively; (D) I-t curves performed of COP_MCT-Co-900 and Pt/C; (E) Hydrogen peroxide yield of COP_MCT-Co, COP_MCT-Co-900 and Pt/C; (F) Electron transfer numbers of COP_MCT-Co, COP_MCT-Co-900 and Pt/C. ORR: Oxygen reduction reaction; LSV: linear sweep voltammetry; COP: covalent organic polymer.