Improved Oxygen Reduction Reaction Performance of Co Confined in Ordered N-Doped Porous Carbon Derived from ZIF-67@PILs

Diffusion and activation of reaction species are two critical factors of oxygen reduction reaction (ORR). Diffusion property is essentially dominated by transmission of reaction species in the channel of catalysts. Herein, we report a facile method to prepare ordered-carbon coated Co nanoparticle (Co@O-NPC). Specifically, we mixed ZIF-67 MOF microcrystal into an ionic liquid monomer which resulted in ZIF-67@PILs composites. Subsequently, Co@O-NPC was obtained by the high-temperature pyrolysis of ZIF-67@PILs. Electrochemical measurements show that it possesses superior ORR property compared to commercial Pt/C. A combination of molecular dynamics (MD) calculations and contrast experimental results reveals that the ordered porous carbon structure can improve the diffusivity of reaction species more effectively than disordered carbon, thereby enhancing ORR property. Moreover, DFT calculation results demonstrate that the catalytically active sites are located on the cavity bottom of Co@O-NPC and uncover the synergistic effect between Co nanoparticles and N-doped porous carbon.