Heat-treated Fe/N/C catalysts for O2 electroreduction:: Are active sites hosted in micropores?
Heat-treated Fe/N/C catalysts for O2 electroreduction:: Are active sites hosted in micropores?
复制标题
DOI：
10.1021/jp057135h
复制
发表时间：
2006-03-23
影响因子：
3.3
通讯作者：
Cai, M
中科院分区：
文献类型：
--
作者：
Jaouen, F;Lefèvre, M;Cai, M
铂的有限供应是燃料电池商业化的潜在威胁。自20世纪70年代以来，通过对碳与非贵金属和氮原子源在T ~ 60 ~ 600℃下进行热处理，获得了电化学还原氧的替代催化剂。然而，热处理激活这些材料的过程仍然是一个悬而未决的问题。在这里，我们报道了炭黑和醋酸铁在NH3中热处理的活化过程包括三个连续的步骤：(i)氮原子进入碳中，（ii）通过碳和氨的反应形成微孔，（iii）通过铁和氨的反应完成微孔中的活性位点。步骤（ii）是最慢的。此外，当碳载体结构中加入足够的氮原子时，每质量催化剂的微孔表面控制着宏观活性。这些事实应该有助于确定活性位点的结构和确定增加这种催化剂的位点密度的方法。
Limited availability of platinum is a potential threat to fuel cell commercialization. Since the 1970s, alternative catalysts to the electrochemical reduction of oxygen have been obtained from heat treatment at T > 600 degrees C of carbon with a non-noble metal and a source of nitrogen atoms. However, the process by which the heat treatment activates these materials remains an open question. Here, we report that the activation process of carbon black and iron acetate heat-treated in NH3 comprises three consecutive steps: (i) incorporation of nitrogen atoms in the carbon, (ii) micropore formation through reaction between carbon and ammonia, and (iii) completion of active sites in the micropores by reaction of iron with ammonia. Step (ii) is the slowest. Moreover, the microporous Surface per mass of catalyst controls the macroscopic activity when enough nitrogen atoms are incorporated in the structure of the carbon Support. These facts should help in determining the structure of the active sites and in identifying methods to increase the site density of such catalysts.