Co- and N-doped carbon nanotubes with hierarchical pores derived from metal–organic nanotubes for oxygen reduction reaction

Abstract Biomolecules with a broad range of structure and heteroatom-containing groups offer a great opportunity for rational design of promising electrocatalysts via versatile chemistry. In this study, uniform folic acid–Co nanotubes (FA–Co NTs) were hydrothermally prepared as sacrificial templates for highly porous Co and N co-doped carbon nanotubes (Co–N/CNTs) with well-controlled size and morphology. The formation mechanism of FA–Co NTs was investigated and FA–Co-hydrazine coordination interaction together with the H-bond interaction between FA molecules was characterized to be the driving force for growth of one-dimensional nanotubes. Such distinct metal–ligand interaction afforded the resultant CNTs rich Co–Nx sites, hierarchically porous structure and Co nanoparticle-embedded conductive network, thus an overall good electrocatalytic activity for oxygen reduction. Electrochemical tests showed that Co–N/CNTs-900 promoted an efficient 4e− ORR process with an onset potential of 0.908 V vs. RHE, a limiting current density of 5.66 mA cm−2 at 0.6 V and a H2O2 yield lower than 5%, comparable to that of 20% Pt/C catalyst. Moreover, the catalyst revealed very high stability upon continuous operation and remarkable tolerance to methanol.