Identification of Catalytic Sites for Oxygen Reduction in Metal/Nitrogen-Doped Carbons with Encapsulated Metal Nanoparticles
Identification of Catalytic Sites for Oxygen Reduction in Metal/Nitrogen-Doped Carbons with Encapsulated Metal Nanoparticles
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DOI：
10.1002/anie.201912275
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发表时间：
2019-11-26
影响因子：
16.6
通讯作者：
Feng, Xinliang
中科院分区：
文献类型：
--
作者：
Chen, Ming-Xi;Zhu, Mengzhao;Feng, Xinliang
开发金属-N-C材料作为有效的非贵金属（NPM）催化剂来催化氧还原反应（ORR）作为铂的替代品对于质子交换膜燃料电池（PEMFC）的实际应用非常重要。然而，金属-N-C材料具有较高的结构异质性。由于其高温合成，它们通常由金属-N-x 位点和石墨烯封装的金属纳米颗粒组成。因此很难确定金属-N-C催化剂的活性结构。在此，我们报告了一种低温NH4Cl处理，可从金属-N-C催化剂中蚀刻出石墨烯封装的纳米粒子，而不破坏共存的原子分散的金属-N-x位点。通过选择性去除金属纳米粒子，大大增强了催化活性。因此，我们可以证实石墨烯封装的纳米颗粒的旁观者作用以及金属-N-C材料中金属-N-x位点对于酸性介质中ORR的关键作用。
The development of metal-N-C materials as efficient non-precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical use of proton exchange membrane fuel cells (PEMFCs). However, metal-N-C materials have high structural heterogeneity. As a result of their high-temperature synthesis they often consist of metal-N-x sites and graphene-encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal-N-C catalysts. Herein, we report a low-temperature NH4Cl-treatment to etch out graphene-encapsulated nanoparticles from metal-N-C catalysts without destruction of co-existing atomically dispersed metal-N-x sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene-encapsulated nanoparticles and the pivotal role of metal-N-x sites in the metal-N-C materials for ORR in the acidic medium.