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

Abstract

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.