Abstract: Multi-walled carbon nanotubes (CNT) modified using TiO₂ nanoparticles (CNT@TiO₂) were prepared. Then, Pt-Au/CNT@TiO₂ catalysts were prepared by a deposition-UV-photoreduction method for direct methanol fuel cells. The physico-chemical properties of the catalysts were characterized by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The catalytic performance was evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The Pt-Au nanoparticles were found to be uniformly deposited onto the CNT@TiO₂ support and had diameters of 2–3 nm. Compared with the Pt-Au/CNT catalyst that was made using a general chemical method, Pt-Au/CNT@TiO₂ exhibits higher CO-tolerance for the following reasons. Firstly, the strong interaction between the Pt-Au alloy and TiO₂ leads to an increase in electron density on the metallic Pt-Au, which transfers electrons to the π_CO^* orbital of CO and weakens C–O binding while the oxidation overpotential is lowered. Secondly, the high-valence Ti ions dissociate water to form OH_ad (ad: adsorbed) species, which then reacts with the strongly bound CO_ad on the Pt surface to form CO₂.

Key words: platinum, gold, titanium dioxide, carbon nanotube, electrocatalyst, direct methanol fuel cell