Fluorine doped CNTs for efficient OER activity outperforming iridium supported carbon electrocatalyst

Herein, we report the low-temperature fluorine doping into carbon nanotubes (CNTs) by solid-state fusion method using xenon fluoride (XeF2) as a precursor of fluorine. The XPS analysis revealed that fluorine atoms were covalently attached to CNTs and about 5.1 at.% fluorine was successfully doped into CNTs. The transmission electron microscope images showed that the outer surface of thinner CNTs becomes rough after fluorine incorporation with a similar tube diameter as that of undoped CNTs. The electrochemical testing for oxygen evolution reaction (OER) in alkaline media shows that the F-doped CNTs are better OER electrocatalysts than their undoped counterpart and noble metal iridium supported carbon electrocatalyst i.e. Ir/C (20 wt% Ir) under identical conditions. The F-doped CNTs exhibited 25 mV and 60 mV lower OER overpotentials than noble metal iridium supported electrocatalyst and undoped CNTs respectively. The better OER performance of F-doped CNTs is attributed to the surface modification of inert sp2 hybridized carbon layers by more electronegative fluorine atoms which create semi ionic C–F and covalent C–F active sites for efficient OER activity.