Germanium and phosphorus co-doped carbon nanotubes with high electrocatalytic activity for oxygen reduction reaction

Abstract

Germanium and phosphorus co-doped carbon nanotubes (Ge–P-CNTs) were prepared by a simple and scalable approach. The morphology and structure of the Ge–P-CNTs was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The ORR electrocatalytic performances were evaluated by exchange current density, reaction pathway selectivity, on-set potential, kinetic current density and H₂O₂ yields from rotating ring-disk electrode (RRDE) measurements, indicating that the co-doped GeP₂C₂, GeP₃C and GeP₄ + PC₃ microstructures in Ge–P-CNTs are crucial to improving the ORR catalytic performance. In fact, the electrochemical performance enhancement results from the synergistic effects by the appropriate proportion of Ge and P atoms. The ORR catalytic synergistic effect has also been verified by calculating the work function based on density functional theory (DFT). Because of these outstanding features, it is expected that the Ge–P-CNTs materials will be a very suitable catalyst for fuel cells and metal–air batteries.