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/H 2 O 2 solution treatment. CNTs functionalized by IMH-assisted HF/H 2 O 2 solution treatment (CNTs-HF/H 2 O 2 ) are characterized by high oxygen-containing groups and high graphitization degree, as compared with CNTs treated by HF (CNTs-HF) or by IMH-assisted H 2 O 2 solution treatment without prior HF treatment (CNTs-H 2 O 2 ). Pt supported on CNTs-HF/H 2 O 2 (Pt/CNTs-HF/H 2 O 2 ) 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-H 2 O 2 and 4.0 nm for Pt supported on pristine CNTs. Pt/CNTs-HF/H 2 O 2 electrocatalysts display a high electrochemical surface area, high Pt utilization efficiency, a superior electrocatalytic and mass activity for the O 2 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/H 2 O 2 solution methods for the functionalization of CNTs, and the method could be easily scaled-up to treat CNTs in large quantities.