Functionalization of carbon nanotubes by an effective intermittent microwave heating-assisted HF/H2O2 treatment for electrocatalyst support of fuel cells

A method is developed to effectively functionalize carbon nanotubes (CNTs) by intermittent microwave heating (IMH)-assisted HF/H2O2 solution treatment. CNTs functionalized by IMH-assisted HF/H2O2 solution treatment (CNTs-HF/H2O2) are characterized by high oxygen-containing groups and high graphitization degree, as compared with CNTs treated by HF (CNTs-HF) or by IMH-assisted H2O2 solution treatment without prior HF treatment (CNTs-H2O2). Pt supported on CNTs-HF/H2O2 (Pt/CNTs-HF/H2O2) has an average particle size of 2.8 nm, smaller than 2.9 nm for Pt supported on CNTs-HF, 3.3 nm for Pt supported on CNTs-H2O2 and 4.0 nm for Pt supported on pristine CNTs. Pt/CNTs-HF/H2O2 electrocatalysts display a high electrochemical surface area, high Pt utilization efficiency, a superior electrocatalytic and mass activity for the O2 reduction reaction (ORR) with respect to other catalyst samples in the present study. The results demonstrate the efficiency and effectiveness of the IMH-assisted HF/H2O2 solution methods for the functionalization of CNTs, and the method could be easily scaled-up to treat CNTs in large quantities.