以TiO2包覆的多壁碳纳米管(CNT@TiO2)为载体,Pt和Au为活性物质,采用沉积紫外光催化还原法制备出高活性的甲醇阳极电催化剂Pt-Au/CNT@TiO2,并采用X射线衍射、透射电镜和X射线光电子能谱对催化剂样品的物化特征进行表征.催化剂的抗毒性能用循环伏安和交流阻抗测试来表征.结果表明,粒径为2～3nm的Pt-Au纳米粒子均匀的分散在CNT@TiO2载体上.与普通化学还原方法制备的Pt-Au/CNT电催化剂相比,Pt-Au/CNT@TiO2催化剂表现出更高的抗毒性.这是因为:(1)Pt-Au合金和TiO2的相互作用使Pt-Au合金的电子密度增加,Pt-Au电子密度的增加会传递部分电子到CO的反键轨道上,从而削弱碳氧键,最终促使过氧化电位降低;(2)高价态的钛离子分解水分子从而形成吸附态的OHad物种,此物种与吸附在Pt表面的CO反应最终生成CO2.
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 πco orbital of CO and weakens C-O binding while the oxidation overpotential is lowered.Secondly,the high-valence Ti ions dissociate water to form OHad (ad:adsorbed) species,which then reacts with the strongly bound COad on the Pt surface to form CO2.
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