Self-Catalyzed Carbon Nanotubes with Dual-Active-Site Co/CoN4 Motifs for High-Efficiency Bifunctional Oxygen Electrocatalysis.

Carbon nanotubes (CNTs) have garnered significant attention due to their large specific surface area and efficient mass transfer properties. However, the construction of well-ordered CNT catalysts with high-efficiency bifunctional oxygen electrocatalytic activity remains a significant challenge. Herein, the uniform size of CNTs with high-density dual-active-site Co/CoN4 motifs (A-Co/Co-NC) is rationally designed and fabricated through an in situ metal-ligand anchoring method (N →  Co2+) followed by a pyrolysis process. The selected 2,6-diaminopurine (DAP) can anchor and disperse Co ions in N sites, which will form uniform CNTs with Co NPs and CoN4 active sites during the pyrolysis process. Theoretical calculation and in situ characteristics clearly proved that Co NP works as an OER active unit and that CoN4 acts as an ORR active site. Benefiting from the high-density dual-active-site Co/CoN4 motifs, the A-Co/Co-NC catalyst displays superior bifunctional performance (ΔE = 0.76 V). Therefore, the A-Co/Co-NC-based zinc-air battery (ZAB) exhibits distinguished reversibility. Remarkably, the A-Co/Co-NC-based Al-air battery (AAB) has a high power density (129.12 mW cm-2). This work provides a feasible design concept to obtain well-organized CNTs with highly dispersed active sites.