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 sp(2) hybridized carbon layers by more electronegative fluorine atoms which create semi ionic C-F and covalent C-F active sites for efficient OER activity.