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Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-N-C Acidic ORR Catalyst and Its in Situ Reduced Fe-N4 Active Site Identification Revealed by X-ray Absorption Spectroscopy
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-02-21 00:00:00 , DOI: 10.1021/acscatal.8b00138 Meiling Xiao 1 , Jianbing Zhu 1 , Liang Ma 2 , Zhao Jin 3 , Junjie Ge 3 , Xin Deng 4 , Yang Hou 4 , Qinggang He 4 , Jingkun Li 5 , Qingying Jia 5 , Sanjeev Mukerjee 5 , Ruoou Yang 6 , Zheng Jiang 6 , Dangsheng Su 7 , Changpeng Liu 3 , Wei Xing 1
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-02-21 00:00:00 , DOI: 10.1021/acscatal.8b00138 Meiling Xiao 1 , Jianbing Zhu 1 , Liang Ma 2 , Zhao Jin 3 , Junjie Ge 3 , Xin Deng 4 , Yang Hou 4 , Qinggang He 4 , Jingkun Li 5 , Qingying Jia 5 , Sanjeev Mukerjee 5 , Ruoou Yang 6 , Zheng Jiang 6 , Dangsheng Su 7 , Changpeng Liu 3 , Wei Xing 1
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Developing highly efficient, low-cost oxygen reduction catalysts, especially in acidic medium, is of significance toward fuel cell commercialization. Although pyrolyzed Fe-N-C catalysts have been regarded as alternatives to platinum-based catalytic materials, further improvement requires precise control of the Fe-Nx structure at the molecular level and a comprehensive understanding of catalytic site structure and the ORR mechanism on these materials. In this report, we present a microporous metal–organic-framework-confined strategy toward the preferable formation of single-atom dispersed catalysts. The onset potential for Fe-N-C is 0.92 V, comparable to that of Pt/C and outperforming most noble-metal-free catalysts ever reported. A high-spin Fe3+-N4 configuration is revealed by the 57Fe Mössbauer spectrum and X-ray absorption spectroscopy for Fe L-edge, which will convert to Fe2+-N4 at low potential. The in situ reduced Fe2+-N4 moiety from high-spin Ox-Fe3+-N4 contributes to most of the ORR activity due to its high turnover frequency (TOF) of ca. 1.71 e s–1 sites–1.
中文翻译：
微孔骨架诱导的单原子分散Fe-NC酸性ORR催化剂的合成及其X射线吸收光谱揭示的原位还原Fe-N 4活性位点鉴定
开发高效，低成本的氧还原催化剂，特别是在酸性介质中，对于燃料电池的商业化具有重要意义。尽管热解的Fe-NC催化剂已被视为铂基催化材料的替代品，但进一步的改进要求在分子水平上精确控制Fe-N x结构，并全面理解这些材料上的催化位点结构和ORR机理。在本报告中，我们提出了一种微孔金属-有机框架限制的策略，以更好地形成单原子分散催化剂。Fe-NC的起始电势为0.92 V，与Pt / C相当，并且胜过以往报道的大多数无贵金属催化剂。高自旋Fe 3+ -N 4Fe L-edge的57 FeMössbauer光谱和X射线吸收光谱揭示了这种构型，它将在低电势下转换为Fe 2+ -N 4。来自高自旋O x -Fe 3+ -N 4的原位还原Fe 2+ -N 4部分由于其高翻转频率（TOF）约为ca。1.71 es –1个站点–1。
更新日期：2018-02-21
中文翻译：
微孔骨架诱导的单原子分散Fe-NC酸性ORR催化剂的合成及其X射线吸收光谱揭示的原位还原Fe-N 4活性位点鉴定
开发高效，低成本的氧还原催化剂，特别是在酸性介质中，对于燃料电池的商业化具有重要意义。尽管热解的Fe-NC催化剂已被视为铂基催化材料的替代品，但进一步的改进要求在分子水平上精确控制Fe-N x结构，并全面理解这些材料上的催化位点结构和ORR机理。在本报告中，我们提出了一种微孔金属-有机框架限制的策略，以更好地形成单原子分散催化剂。Fe-NC的起始电势为0.92 V，与Pt / C相当，并且胜过以往报道的大多数无贵金属催化剂。高自旋Fe 3+ -N 4Fe L-edge的57 FeMössbauer光谱和X射线吸收光谱揭示了这种构型，它将在低电势下转换为Fe 2+ -N 4。来自高自旋O x -Fe 3+ -N 4的原位还原Fe 2+ -N 4部分由于其高翻转频率（TOF）约为ca。1.71 es –1个站点–1。
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