Oxygen reduction catalysts for polymer electrolyte fuel cells from the pyrolysis of iron acetate adsorbed on various carbon supports
Oxygen reduction catalysts for polymer electrolyte fuel cells from the pyrolysis of iron acetate adsorbed on various carbon supports
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DOI：
10.1021/jp021634q
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发表时间：
2003-02-13
影响因子：
3.3
通讯作者：
Lindbergh, G
中科院分区：
文献类型：
--
作者：
Jaouen, F;Marcotte, S;Lindbergh, G
在酸性介质中，通过在19个碳载体上吸附乙酸铁（II）制备了用于氧电化学还原的非贵金属催化剂。然后将这些材料在含有NH3的气氛中热解。这19种碳载体是（i）六种原样商业载体（Printex XE-2、Norit SX Ultra、Ketjenblack EC-600 JD、乙炔黑、Vulcan XC-72 R和Black Pearls 2000），（ii）三种原样开发载体（Lonza HS 300和Sid Richardson RC 1和RC 2），（iii）在900 ℃下在含有NH3的气氛中预热解相同的九种前述载体以增加它们的N含量，和（iv）通过在900 ℃下在含有NH 3的气氛中热解二萘嵌苯四羧酸二酐而制备的合成碳。本研究的目的是确定碳载体对催化剂的催化活性的影响。测定了19种催化剂的比表面积、孔径分布、N和O含量以及电催化活性。结果发现，催化剂的活性从一个碳载体到另一个变化很大，但无论是催化剂的比表面积还是它们的大孔或中孔的分布都不是催化活性的决定因素。最重要的因素是材料的N含量; N含量越高，其表面上的催化位点密度越高，电催化剂越好。然而，缺乏N的碳载体显示出一些较低的催化活性，这归因于铁氧化物。后一种催化位点也出现在其它含N催化剂中。因此，在这些材料中，有三个催化位点在起作用：一个氧化铁位点和两个含氮位点，标记为FeN 4/C和FeN 2/C，最后一个位点对氧电还原最具活性。
Nonnoble metal catalysts for the electrochemical reduction of oxygen in acidic medium have been produced by adsorbing iron(II) acetate on 19 carbon supports. These materials were then pyrolyzed in an atmosphere containing NH3. The 19 carbon supports are (i) six as-received commercial supports (Printex XE-2, Norit SX Ultra, Ketjenblack EC-600JD, acetylene black, Vulcan XC-72R, and Black Pearls 2000), (ii) three as-received developmental supports (Lonza HS300 and Sid Richardson RC1 and RC2), (iii) the same nine previous supports prepyrolyzed at 900degreesC in an atmosphere containing NH3 to increase their N content, and (iv) a synthetic carbon made by pyrolyzing perylene tetracarboxylic dianhydride at 900degreesC in an atmosphere containing NH3. The goal of this study is to determine the effect of the carbon support on the catalytic activity of the catalysts. The specific surface area, the pore size distribution, the N and O contents, and the electrocatalytic activities of the 19 types of catalysts were measured. It was found that the activity of the catalysts varies greatly from one carbon support to another, but neither the specific surface area of the catalysts nor the distribution of their macro- or mesopores is a determining factor for the catalytic activity. The most important factor is the N content of the materials; the higher it is, the higher is the density of the catalytic sites on their surface and the better is the electrocatalyst. Carbon supports that are devoid of N, however, display some lower catalytic activity, which is attributed to an iron oxide. The latter catalytic site occurs also in the other N-containing catalysts. In these materials there are, therefore, three catalytic sites at work: an iron oxide site and two N-containing sites labeled FeN4/C and FeN2/C, with the last site being the most active for oxygen electroreduction.