Metal‐Free Halogen‐Engineered Carbon Nanotubes for Highly Efficient Oxygen Reduction Reaction

Exploration of platinum‐free‐based electrocatalysts for high‐performance oxygen reduction reaction (ORR) is tremendously attractive toward the large‐scale practical applications, yet greatly challenging. Herein, it is demonstrated that halogen doping on carbon nanotube (CNT) could be an effective pathway toward activation of oxygen reduction reaction performance. A novel synergistic molten‐salt strategy using a NaCl eutectic mixture to precisely fabricate Cl‐doped, defective CNTs is developed, allowing for the creation of a high density of topological defects, a large specific surface area, and hierarchical porosity. The as‐prepared Cl‐CNT catalyst exhibits exceptional ORR activity in alkaline media, with a half‐wave potential of 0.84 V (vs RHE), outperforming most metal‐free carbon‐based catalysts and rivaling commercial Pt/C. It further demonstrates high selectivity for the direct 4e ⁻ pathway (>95%) and excellent methanol tolerance and durability. When deployed in a zinc–air battery, it delivers a peak power density of 156 mW cm ⁻² and remarkable cycling durability over 120 hours. The experimental results are consistent with the density functional theory (DFT) screening predication that Cl doping optimally modifies the electronic structure and binding energy of oxygen intermediates, leading to the remarkable reaction kinetics. This work provides both fundamental insight and a scalable synthetic paradigm for harnessing halogen doping in advanced metal‐free electrocatalysis.