Long-Range Electron Transfer over Graphene-Based Catalyst for High-Performing Oxygen Reduction Reactions: Importance of Size, N-doping, and Metallic Impurities
Long-Range Electron Transfer over Graphene-Based Catalyst for High-Performing Oxygen Reduction Reactions: Importance of Size, N-doping, and Metallic Impurities
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DOI：
10.1021/ja5033474
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发表时间：
2014-06-25
影响因子：
15
通讯作者：
Woo, Seong Ihl
中科院分区：
文献类型：
--
作者：
Choi, Chang Hyuck;Lim, Hyung-Kyu;Woo, Seong Ihl
氮掺杂碳材料由于其长期稳定性和低成本而被认为是下一代燃料电池氧还原反应（ORR）催化剂。然而，这些催化剂的潜在机理还没有得到充分的鉴定，阻碍了高性能催化剂的合理设计。在这里，我们表明，第一个电子被转移到O-2分子的外亥姆霍兹平面（ET-OHP）在很长的范围内。这与传统观点形成鲜明对比，传统观点认为O-2吸附必须先于ET步骤，因此活性位点必须具有与金属催化剂上发生的O-2结合特性一样好的O-2结合特性。基于ET-OHP机制，电极电位的位置主要表征ORR活性。因此，我们证明了可以通过减小石墨烯尺寸和/或包括金属杂质来提高电极电势，从而增强ORR活性，这可以转移到具有上级稳定性的单电池操作中。
N-doped carbon materials are considered as next-generation oxygen reduction reaction (ORR) catalysts for fuel cells due to their prolonged stability and low cost. However, the underlying mechanism of these catalysts has been only insufficiently identified, preventing the rational design of high-performing catalysts. Here, we show that the first electron is transferred into O-2 molecules at the outer Helmholtz plane (ET-OHP) over a long range. This is in sharp contrast to the conventional belief that O-2 adsorption must precede the ET step and thus that the active site must possess as good an O-2 binding character as that which occurs on metallic catalysts. Based on the ET-OHP mechanism, the location of the electrode potential dominantly characterizes the ORR activity. Accordingly, we demonstrate that the electrode potential can be elevated by reducing the graphene size and/or including metal impurities, thereby enhancing the ORR activity, which can be transferred into single-cell operations with superior stability.