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Electrochemical Evidence for Two Sub‐families of FeNxCy Moieties with Concentration‐Dependent Cyanide Poisoning
ChemElectroChem ( IF 3.5 ) Pub Date : 2018-03-05 , DOI: 10.1002/celc.201800067 Min Wook Chung 1 , Gajeon Chon 1 , Hyungjun Kim 2 , Frédéric Jaouen 3 , Chang Hyuck Choi 1
ChemElectroChem ( IF 3.5 ) Pub Date : 2018-03-05 , DOI: 10.1002/celc.201800067 Min Wook Chung 1 , Gajeon Chon 1 , Hyungjun Kim 2 , Frédéric Jaouen 3 , Chang Hyuck Choi 1
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Iron‐nitrogen‐carbon (Fe−N−C) catalysts are one of the most promising family of materials for the successful replacement of noble Pt in low‐temperature fuel cells. Despite recent advances in the synthesis, activity, and site‐structure of Fe−N−C catalysts, further improved understanding of the nature of the Fe‐based active sites is still needed. In the present study, the existence of two sub‐families of FeNxCy moieties is revealed by the concentration dependence of cyanide poisoning on a Fe−N−C catalyst only comprising of atomically dispersed iron. The analysis of the activity decrease upon contact with various cyanide concentrations and activity recovery following rinsing with water reveals the presence of two sub‐groups of ORR‐active FeNxCy species. They are discriminated by the reversibility or irreversibility of the cyanide poisoning. From a Mössbauer spectroscopy study and poisoning test on a model compound, Fe(II) phthalocyanine (FePc), we hypothesize that the reversibility/irreversibility of cyanide poisoning is governed by the competitive adsorption of oxygen molecule and cyanide anion. It is proposed that FeNxCy moieties with Fe in low spin state reversibly adsorb cyanide, whereas those with a medium spin state irreversibly adsorb cyanide.
中文翻译：
浓度依赖性氰化物中毒的两个FeNxCy部分亚家族的电化学证据
铁氮碳（Fe-N-C）催化剂是成功替代低温燃料电池中贵金属Pt的最有希望的材料系列之一。尽管最近在Fe-N-C催化剂的合成，活性和位点结构方面取得了进步，但仍需要进一步提高对基于Fe的活性位点性质的认识。在本研究中，FeN x C y部分的两个亚家族的存在是由氰化物中毒对仅包含原子分散铁的Fe-N-C催化剂的浓度依赖性揭示的。与各种氰化物浓度接触后活性降低的分析以及用水冲洗后的活性恢复表明，存在两个具有ORR活性的FeN x C y亚类物种。通过氰化物中毒的可逆性或不可逆性来区分它们。通过对模型化合物Fe（II）酞菁（FePc）进行的Mössbauer光谱研究和中毒测试，我们假设氰化物中毒的可逆性/不可逆性受氧分子和氰化物阴离子的竞争性吸附控制。提出具有低自旋态的Fe的FeN x C y部分可逆地吸附氰化物，而具有中自旋态的那些不可逆地吸附氰化物。
更新日期：2018-03-05
中文翻译：
浓度依赖性氰化物中毒的两个FeNxCy部分亚家族的电化学证据
铁氮碳（Fe-N-C）催化剂是成功替代低温燃料电池中贵金属Pt的最有希望的材料系列之一。尽管最近在Fe-N-C催化剂的合成，活性和位点结构方面取得了进步，但仍需要进一步提高对基于Fe的活性位点性质的认识。在本研究中，FeN x C y部分的两个亚家族的存在是由氰化物中毒对仅包含原子分散铁的Fe-N-C催化剂的浓度依赖性揭示的。与各种氰化物浓度接触后活性降低的分析以及用水冲洗后的活性恢复表明，存在两个具有ORR活性的FeN x C y亚类物种。通过氰化物中毒的可逆性或不可逆性来区分它们。通过对模型化合物Fe（II）酞菁（FePc）进行的Mössbauer光谱研究和中毒测试，我们假设氰化物中毒的可逆性/不可逆性受氧分子和氰化物阴离子的竞争性吸附控制。提出具有低自旋态的Fe的FeN x C y部分可逆地吸附氰化物，而具有中自旋态的那些不可逆地吸附氰化物。
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