Synthesis of multiwall carbon nanotube-supported platinum catalysts by solution plasma processing for oxygen reduction in polymer electrolyte fuel cells

Two preparation methods with solution plasma (SP) processing were carried out to produce Pt nanoparticles (PtNPs) on multi-wall carbon nanotubes (MWCNTs). One is the method that PtNPs were attached on MWCNTs using a SP irradiation after PtNPs were solely produced by a SP irradiation. The other is that the formation of PtNPs on MWCNTs was performed using a SP irradiation after a Pt precursor was adsorbed on MWCNTs. PtNPs were well anchored and uniformly dispersed on the MWCNTs prepared by using the latter method. The average sizes of PtNPs estimated by transmittance electron microscopy (TEM) images were about 5 to 9 nm with the former method and about 2 to 3 nm with the latter method, respectively. It was revealed that the bulk of PtNPs produced by a solution plasma irradiation is in metal state analyzed on the basis of X-ray diffraction (XRD) measurements. An accelerated durability test was performed using a saw-tooth potential wave. Apparent degradation rates of Pt/MWCNTs prepared by the methods toward oxygen reduction activity were smaller than that of 20% Pt-XC72R.