High efficiency nitrogen doping and single atom cobalt anchoring via supermolecules for oxygen reduction electrocatalysis

Single atom catalysts (SACs) stabilized by nitrogen in a carbon support and having maximized atom utilization efficiency and an unsaturated environment exhibit high catalytic activity and selectivity. Incorporating nitrogen into the carbon lattice efficiently and uniformly is a critical step in preparing such catalysts but is challenging. The synthesis of Co and N co-doped porous carbon nanospheres (CoN-PCNS) in which Co is dispersed on the atomic scale is described herein, based on the facile pyrolysis of a mixture of cyclodextrin-based supermolecules with CoCl2. Non-covalent host-guest interactions between cyclodextrin and p-phenylenediamine in the supramolecular complex give optimal nitrogen species mobility and retention. These factors enable a thorough reaction between nitrogen and carbon during crosslinking to give ultrahigh nitrogen doping efficiency, with approximately 57% nitrogen retention upon pyrolysis and consequently a homogeneous dispersion of coordinated CoN4 sites throughout the carbon matrix. The CoN-PCNS exhibits impressive electrocatalytic activity during oxygen reduction, with an onset potential of 0.93 V, limiting current density of 5.74 mA cm(-2), good methanol tolerance and negligible activity decay under alkaline conditions after 10 000 voltage cycles. Density functional theory calculations suggest that CoN4 is the most active among the various sites.

Automated summary

This study describes the synthesis of Co and N co-doped porous carbon nanospheres with efficient nitrogen retention and homogeneous dispersion of CoN4 sites, resulting in impressive electrocatalytic performance during oxygen reduction. The non-covalent interactions between cyclodextrin and p-phenylenediamine play a crucial role in optimizing nitrogen species mobility and retention, leading to a high nitrogen doping efficiency of approximately 57%. Density functional theory calculations suggest that CoN4 is the most active site among various sites considered.