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Mechanisms of the oxygen reduction reaction on B- and/or N-doped carbon nanomaterials with curvature and edge effects†
Nanoscale ( IF 5.8 ) Pub Date : 2017-12-18 00:00:00 , DOI: 10.1039/c7nr08061a Xiaolong Zou 1, 2, 3, 4, 5 , Luqing Wang 1, 2, 3, 4, 5 , Boris I. Yakobson 1, 2, 3, 4, 5
Nanoscale ( IF 5.8 ) Pub Date : 2017-12-18 00:00:00 , DOI: 10.1039/c7nr08061a Xiaolong Zou 1, 2, 3, 4, 5 , Luqing Wang 1, 2, 3, 4, 5 , Boris I. Yakobson 1, 2, 3, 4, 5
Affiliation
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Despite recent increased research interest in hetero-atom (B and/or N) doping effects on the oxygen reduction reaction (ORR) performance of carbon nanomaterials, microscopic understanding of active catalytic sites and effects of B and/or N doping has not been conclusively reached. Here, through comparative first-principles simulations between BN codoping and isolated B or N doping in both graphene nanoribbons (GNRs) and carbon nanotubes (CNTs), we not only identify active sites in these doped carbon nanomaterials, but elucidate the underlying mechanism of ORR processes. While the distortion of C–C bonds in CNTs leads to strong binding of O2, spin density distribution along the edges plays a key role in enhancing the adsorption strength of O2 on GNRs. The effective adsorption of O2 facilitates the following elementary reduction reactions. Based on thermodynamic analyses, O2 adsorption as well as the electron and proton transfer to O atom are identified as key rate-determining steps. For CNTs, a good linear scaling is found between the adsorption energies of key intermediate products and that of atomic O, and thus the latter serves as a good descriptor for ORR activities. Further, N-doped high-quality CNTs are shown to exhibit best performance. For GNRs, due to edge effects, the linear relationship is broken, which promotes the catalytic activities in the BN codoping case. These findings resolve the long-standing controversy on the synergetic effects of B and N codoping, which deepens our understanding of the reaction mechanism. This work might further facilitate the optimization of the doping strategies for high-efficiency carbon-based ORR catalysts.
中文翻译：
含B和/或N掺杂的碳纳米材料上具有曲率和边缘效应的氧还原反应机理†
尽管最近人们对杂原子（B和/或N）掺杂对碳纳米材料的氧还原反应（ORR）性能的研究兴趣不断提高，但对活性催化位点和B和/或N掺杂的影响的微观理解尚无定论。到达。在这里，通过在石墨烯纳米带（GNR）和碳纳米管（CNT）中BN共掺杂与孤立的B或N掺杂之间的比较第一性原理模拟，我们不仅识别了这些掺杂的碳纳米材料中的活性位点，而且阐明了ORR的潜在机理流程。尽管碳纳米管中的C–C键变形会导致O 2牢固结合，但沿边缘的自旋密度分布在增强O 2在GNR上的吸附强度方面起着关键作用。有效吸附O图2促进以下基本还原反应。根据热力学分析，O 2吸附以及电子和质子转移到O原子被确定为决定速率的关键步骤。对于CNT，在关键中间产物的吸附能和原子O的吸附能之间发现了良好的线性比例，因此后者可作为ORR活性的良好描述。此外，显示出N掺杂的高质量CNT表现出最佳性能。对于GNR，由于边缘效应，线性关系被破坏，这在BN共掺杂情况下促进了催化活性。这些发现解决了关于B和N共掺杂协同作用的长期争论，这加深了我们对反应机理的理解。这项工作可能会进一步促进针对高效碳基ORR催化剂的掺杂策略的优化。
更新日期：2017-12-18
中文翻译：
含B和/或N掺杂的碳纳米材料上具有曲率和边缘效应的氧还原反应机理†
尽管最近人们对杂原子（B和/或N）掺杂对碳纳米材料的氧还原反应（ORR）性能的研究兴趣不断提高，但对活性催化位点和B和/或N掺杂的影响的微观理解尚无定论。到达。在这里，通过在石墨烯纳米带（GNR）和碳纳米管（CNT）中BN共掺杂与孤立的B或N掺杂之间的比较第一性原理模拟，我们不仅识别了这些掺杂的碳纳米材料中的活性位点，而且阐明了ORR的潜在机理流程。尽管碳纳米管中的C–C键变形会导致O 2牢固结合，但沿边缘的自旋密度分布在增强O 2在GNR上的吸附强度方面起着关键作用。有效吸附O图2促进以下基本还原反应。根据热力学分析，O 2吸附以及电子和质子转移到O原子被确定为决定速率的关键步骤。对于CNT，在关键中间产物的吸附能和原子O的吸附能之间发现了良好的线性比例，因此后者可作为ORR活性的良好描述。此外，显示出N掺杂的高质量CNT表现出最佳性能。对于GNR，由于边缘效应，线性关系被破坏，这在BN共掺杂情况下促进了催化活性。这些发现解决了关于B和N共掺杂协同作用的长期争论，这加深了我们对反应机理的理解。这项工作可能会进一步促进针对高效碳基ORR催化剂的掺杂策略的优化。
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