Boron/Nitrogen\nCo-Doped Helically Unzipped Multiwalled Carbon Nanotubes as Efficient\nElectrocatalyst for Oxygen Reduction

Abstract

Bamboo structured\nnitrogen doped multiwalled carbon nanotubes have been helically unzipped,\nand nitrogen doped graphene oxide nanoribbons (CN_<i>x</i>-GONRs) with a multifaceted microstructure have been obtained.\nCN_<i>x</i>-GONRs have then been codoped with\nnitrogen and boron by simultaneous thermal annealing in ammonia and\nboron oxide atmospheres, respectively. The effects of the codoping\ntime and temperature on the concentration of the dopants and their\nfunctional groups have been extensively investigated. X-ray photoelectron\nspectroscopy results indicate that pyridinic and BC₃ are\nthe main nitrogen and boron functional groups, respectively, in the\ncodoped samples. The oxygen reduction reaction (ORR) properties of\nthe samples have been measured in an alkaline electrolyte and compared\nwith the state-of-the-art Pt/C (20%) electrocatalyst. The results\nshow that the nitrogen/boron codoped graphene nanoribbons with helically\nunzipped structures (CN_<i>x</i>/CB_<i>x</i>-GNRs) can compete with the Pt/C (20%) electrocatalyst\nin all of the key ORR properties: onset potential, exchange current\ndensity, four electron pathway selectivity, kinetic current density,\nand stability. The development of such graphene nanoribbon-based electrocatalyst\ncould be a harbinger of precious metal-free carbon-based nanomaterials\nfor ORR applications.