Hierarchical carbon material of N-doped carbon quantum dots in-situ formed on N-doped carbon nanotube for efficient oxygen reduction

A facile one-pot hydrothermal method was proposed to fabricate nitrogen-doped carbon quantum dots (N-doped CQDs) on the surface of nitrogen-doped carbon nanotube (N-doped CNTs). The microstructure of the N-doped CQDs/N-doped CNTs hybrid was investigated by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, their electrocatalytic activity of the N-doped CQDs/N-doped CNTs hybrid in oxygen reduction reaction (ORR) was systematically evaluated and it was found that the N-doped CQDs/N CNTs hybrid deposited as such exhibits a high performance for ORR in terms of a low onset potential of −0.03 V vs. Ag/AgCl, a high limiting diffusion current density of ~5.5 mA cm⁻², and a one-step 4e ORR process, holding great potential for future metal-free catalysts.