Carbon nanotubes supported Pt-Au catalysts for methanol-tolerant oxygen reduction reaction: A comparison between Pt/Au and PtAu nanoparticles

Two kinds of Pt-Au/CNT catalysts with different structures are prepared by synthesizing the formerly separated Pt/Au (Au separating Pt) in separate solutions, and PtAu nanoparticles in mixed solution using the borohydride reduction method with trisodium citrate as the stabilizing agent, and then depositing the metal colloid nanoparticles on the carbon nanotubes supporting material. The structural information and particle size are characterized by UV-vis absorption spectra, transmission electron microscopy (TEM), and X-ray diffraction (XRD). The results confirm the formation of Pt-Au nanoparticles with PtAu and separated Pt/Au structures. The catalytic activities for methanol oxidation reaction and oxygen reduction reaction are examined by electrochemical measurements. Compared with the Pt/CNT catalyst, the two Pt-Au/CNT catalysts show a lower overpotential for the oxygen reduction reaction in the presence of methanol, indicating a higher methanol tolerance on Au-modified Pt nanoparticles. Particularly, the Pt/Au/CNT catalyst with Au separating Pt nanoparticles structure exhibits the significantly higher methanol tolerance than PtAu/CNT catalyst. The enhanced methanol tolerance may be attributed to less methanol adsorption on Pt surface due to the effect of Au nanoparticles.