Unveiling N-protonation and anion-binding effects on Fe/N/C-catalysts for O(2) reduction in PEM fuel cells.
Unveiling N-protonation and anion-binding effects on Fe/N/C-catalysts for O(2) reduction in PEM fuel cells.
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DOI：
10.1021/jp2042526
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发表时间：
2011-11-18
影响因子：
3.7
通讯作者：
Mukerjee, Sanjeev
中科院分区：
文献类型：
--
作者：
Herranz, Juan;Jaouen, Frederic;Lefevre, Michel;Kramm, Ulrike I.;Proietti, Eric;Dodelet, Jean-Pol;Bogdanoff, Peter;Fiechter, Sebastian;Abs-Wurmbach, Irmgard;Bertrand, Patrick;Arruda, Thomas M.;Mukerjee, Sanjeev
如果基于铂的催化剂被基于铁的替代品代替，质子交换型燃料电池的高成本将大大降低，而基于铁的替代品最近表现出可比的减少氧气活性，但在酸性培养基中的活性衰减原因是难以捉摸的。在这里，我们揭示了通过NH3中的热解制备的Fe/N/C-催化剂的活性主要由耐酸的Fen4位点赋予其降低O2的离心频率，可以通过催化剂表面的细胞化学变化来调节。我们表明表面N组在pH 1处质子化并随后结合阴离子。这导致O2减少的活性下降。阴离子可以化学或热去除，从而恢复耐酸的Fen4位点的活性。这些结果被解释为当特定表面N组质子酸盐时，FEN4点的周转频率增加。这些前所未有的发现为稳定迄今已知的最活跃的FE/N/C催化剂提供了新的观点。
The high cost of proton-exchange-membrane fuel cells would be considerably reduced if platinumbased catalysts were replaced by iron-based substitutes, which have recently demonstrated comparable activity for oxygen reduction, but whose cause of activity decay in acidic medium has been elusive. Here, we reveal that the activity of Fe/N/C-catalysts prepared through a pyrolysis in NH3 is mostly imparted by acid-resistant FeN4-sites whose turnover frequency for the O2 reduction can be regulated by fine chemical changes of the catalyst surface. We show that surface N-groups protonate at pH 1 and subsequently bind anions. This results in decreased activity for the O2 reduction. The anions can be removed chemically or thermally, which restores the activity of acid-resistant FeN4-sites. These results are interpreted as an increased turnover frequency of FeN4-sites when specific surface N-groups protonate. These unprecedented findings provide new perspective for stabilizing the most active Fe/N/C-catalysts known to date.
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影响因子：
3.7
作者：
Koslowski, Ulrike I.;Abs-Wurmbach, Irmgard;Bogdanoff, Peter
通讯作者：
Bogdanoff, Peter
影响因子：
3.3
作者：
Jaouen, F;Lefèvre, M;Cai, M
通讯作者：
Cai, M
影响因子：
4.5
作者：
Bron, M;Radnik, J;Fiechter, S
通讯作者：
Fiechter, S
影响因子：
3.7
作者：
Jaouen, Frederic;Dodelet, Jean-Pol
通讯作者：
Dodelet, Jean-Pol
影响因子：
4.5
作者：
Baranton, S;Coutanceau, C;Léger, JM
通讯作者：
Léger, JM