Monovacancy Coupled Pyridinic N Site Enables Surging Oxygen Reduction Activity of Metal-Free CNx Catalyst

Nitrogen-doped carbon (CNx) nanostructures are appealing metal-free electrocatalysts for some key electrochemical processes such as oxygen reduction reaction (ORR), due to their low cost, exceptional stability, and desirable selectivity. However, the precise configuration engineering of N-related active sites still remains a big challenge. Herein, we report a concept of monovacancy coupled pyridinic N (MV-c-PN) active site, which is designed and successfully fabricated by the pyrolysis of well-designed precursor. This unique active site couples the features of pyridinic N and topological monovacancy defect, synergistically tuning the electronic properties of CNx moiety. This tuning induces stronger adsorption of oxygen-containing intermediates on the MV-c-PN sites and alters the ORR kinetics pathway. Additionally, the hierarchical porous nature of CNx nanostructure facilitates the penetration of electrolyte and the transportation of O-2. Accordingly, the CNx nanomaterial with such MV-c-PN sites shows outstanding ORR activity in alkaline solution, surpassing most of the reported metal-free catalysts, with its intrinsic turnover frequency (TOF) 7.26 times higher than conventional pyridinic N. The assembled zinc-air battery reaches a maximum power density even 40.3% higher than that with the benchmark Pt/C. Our fine configuration engineering of CNx active sites provides a novel strategy for developing efficient carbon-based metal-free ORR catalysts.

Automated summary

This study presents a novel nitrogen-doped carbon nanostructure with monovacancy coupled pyridinic N as active sites, showing outstanding oxygen reduction reaction activity in alkaline solution. By finely tuning the configuration engineering of active sites, the design surpasses the catalytic activity of conventional pyridinic N, providing a new strategy for developing efficient carbon-based metal-free ORR catalysts.