N-doped pitch assisted local interface micro-environment tailoring and microcrystalline regulation in carbon nanotube for efficient oxygen reduction reaction

Regulating the atomic micro-environment at active sites and the interfaces between carbon nanoparticles is crucial for enhancing the performance of carbon-based metal-free electrocatalysts. Herein, a novel carbon nanocomposite, nitrogen-doped coal tar pitch composite carbon nanotubes (NPC@CNTs) was proposed, along with the potential synergistic mechanisms at its heterojunction interfaces. The innovative synthesis involves encapsulating carbon nanotubes (CNTs) within coal tar pitch (CTP), followed by nitrogen doping and CO 2 activation to form a layered nano-microstructure with hierarchical porosity. This configuration allows for the precise modulation of the atomic environment at the graphitic-N sites within the heterostructure, with the interfacial effects significantly promoting efficient electron transfer and mass transport. The NPC@CNTs exhibit high E onset (0.991 V verse Reversible Hydrogen Electrode) and E half-wave (0.845 V vs RHE) in alkaline solution . with an OER overpotential of 391 mV at 10 mA cm −2 . Furthermore, a Zn–air battery employing NPC@CNTs indicates a peak power density of 91 mW cm −2 with sustained stability over 230 h. Density Functional Theory (DFT) calculations confirmed the heterostructure of graphitic nitrogen-doped CNTs provides a higher density of active sites and more efficient charge transfer at carbon atoms adjacent to nitrogen. The CNTs with functionalized shell-interface has significant potential for bifunctional catalysis, surpassing most heteroatom-doped nanocarbon catalysts and commercial Pt/C (20 %).