Monovacancy Coupled Pyridinic N Site Enables Surging Oxygen Reduction Activity of Metal-Free CN<sub><i>x</i></sub> Catalyst
Zhenzhen Duan, Guokang Han, Hua Huo, Zeyu Lin, Liping Ge, Chunyu Du, Yunzhi Gao, Geping Yin
Abstract
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 O2. 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.