新型碳材料作为直接醇类燃料电池催化剂载体的评述

New Carbon Materials as Catalyst Supports in Direct Alcohol Fuel Cells

电催化反应过程涉及固、液、气传输以及电子和质子传导,为确保反应的顺利进行和提高催化剂中贵金属的利用率及延长催化剂的寿命,理想的电催化剂载体必须同时具备高比表面积、导电性好、合适的孔结构、耐腐蚀以及合适的表面基团等.为此,碳载体的改性工作受到关注,常用的方法是通过酸、碱、氧化和高分子等手段改变载体的结构和表面性质,以期接近理想电催化剂载体的要求;同时在开发新型碳载体方面做了更大量的工作.本文简要评述了商品炭载体如碳黑Vulcan XC-72R以及其它的乙炔黑、黑珍珠-2000、Printex XE-2和Ketjen Black EC等碳材料在直接醇燃料电池中的应用,但对纳米碳纤维、碳纳米管、有序多孔碳、中间相碳小球、碳纳米角、碳纳米卷和碳气凝胶等新型碳载体则进行了较全面的评述.与商品碳载体相比,新型碳载体在一定程度上都表现出比XC-72R更优的性能,这主要是因为新型碳材料具有特殊的结构、更高的结晶性能(导电性)和更好的传质能力.

Electrocatalytic reactions in direct alcohol fuel cells involve solid, liquid, and gas phase transport and electron and proton transfer. Better supports for the electrocatalysts are needed to carry out the reactions successfully and give a longer lifetime for the electrocatalysts. An ideal carbon support should have a high specific surface area, good electric conductivity, suitable pore size, favorable surface functional groups, good corrosion resistance, and low cost. Much work has been done on developing new carbon materials and modifying the carbon materials by pretreatment with acid, alkali, oxidant, or polymer to meet these requirements. In this work, commercial carbon supports that include the widely used carbon black Vulcan XC-72R, acetylene black, black pearls 2000, Printex XE-2, and Ketjen Black EC were briefly reviewed. New carbon materials such as carbon nanofibers, carbon nanotubes, ordered porous carbon, mesocarbon microbeads, carbon nanohorns, carbon nanocoils, and carbon aerogels were reviewed in detail. These new carbon materials generally give better performance due to their special structure, better crystallinity, and faster mass transfer when compared to the commercial materials, and carbon nanotubes demonstrated the best performance up to the present time.