Topological defect and sp³/sp² carbon interface derived from ZIF-8 with linker vacancies for oxygen reduction reaction

Defects in nanocarbon materials can trigger their intriguing electrochemical properties and potential applications, but their synthesis is challenging. Herein, we report the synthesis of ultrathin nitrogen-doped carbon nanosheets with intrinsic defects through the pyrolysis of ZIF-8 with linker vacancies. The as-synthesized electrocatalyst exhibits excellent oxygen reduction reaction (ORR) activity with an onset potential and half-wave potential of 1.05 and 0.873 V vs. RHE, respectively, outperforming the reported metal-free ORR electrocatalysts. It also shows a commercial Pt/C-comparable performance in zinc–air battery with a power density of 154.4 mW cm−2. Characterization and DFT calculation results suggest the adjacent sp3-carbon in carbon pentagon can significantly strengthen the adsorption and activation of oxygen molecules on sp2-carbon, hence the potential determining step is altered and ORR overpotential is lowered. This work highlights a promising green synthesis strategy of MOF-derived metal-free nanocarbon materials for wide application in advanced energy technologies.