Functionalization of Metal-Supported Graphene by an N-Heterocyclic Carbene
Functionalization of Metal-Supported Graphene by an N-Heterocyclic Carbene
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DOI：
10.1021/acs.jpcc.2c02342
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发表时间：
2022-08-19
影响因子：
3.7
通讯作者：
McBreen，Peter H.
中科院分区：
文献类型：
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作者：
Zhang，Tianchi;Khomane，Sonali B.;McBreen，Peter H.
描述了通过N-杂环卡宾（NHC）在Pt（111）和Ru（0001）衬底上官能化石墨烯（Gr）。使用反射吸收红外光谱（RAIRS）的形成，热稳定性，和键合几何的接枝NHC探测。卡宾含有CF 3取代基，其提供了一组三个非常强的吸收带，用于监测化学修饰。通过使用Pt（111）和Ru（0001）衬底，可以比较明显不同的石墨烯系统：虽然石墨烯在Pt（111）上形成了准独立的p型掺杂层，但它与Ru（0001）的相互作用涉及周期性的化学键合以形成n型掺杂层。RAIRS数据表明，苯并咪唑鎓碳酸氢盐前体转化为相对较强吸附的NHC上的两个系统。在300-350 K下清洁形成的表面卡宾归因于由来自支撑的石墨烯层的电子转移激活的过程。在全覆盖的Gr/Pt（111）上，归因于NHC的RAIRS信号在加热到450 K时消失，而在400 K时，它从Gr/Ru（0001）上消失。热稳定性的差异被解释为电子供体NHC与Ru（0001）上的n掺杂石墨烯层的较弱键合。使用氧插层将石墨烯与Ru（0001）解耦以形成p掺杂层来探索该假设。该研究概述了一种修饰石墨烯的方法，并揭示了吸附的NHC的振动光谱提供了一种高度灵敏的方法来探测和区分不同的石墨烯-金属系统。
The functionalization of graphene (Gr) on Pt(111) and Ru(0001) substrates by an N-heterocyclic carbene (NHC) is described. The formation, thermal stability, and bonding geometry of the grafted NHC were probed using reflection absorption infrared spectroscopy (RAIRS). The carbene contains a CF3substituent, which provides a set of three very strong absorption bands with which to monitor the chemical modification. By employing Pt(111) and Ru(0001) substrates, it is possible to compare markedly different graphene systems: while graphene forms a quasi-freestanding p-doped layer on Pt(111), its interaction with Ru(0001) involves periodic chemical bonding to form an n-doped layer. The RAIRS data show that the benzimidazolium hydrogen carbonate precursor transforms to a relatively strongly adsorbed NHC on both systems. Clean formation of the surface carbene at 300–350 K is attributed to a process activated by electron transfer from the supported graphene layer. The RAIRS signal attributed to the NHC on full-coverage Gr/Pt(111) is removed on heating to ∼450 K, while it disappears from Gr/Ru(0001) at ∼400 K. The difference in thermal stability is interpreted in terms of weaker bonding of the electron-donor NHC to the n-doped graphene layer on Ru(0001). This hypothesis is explored using oxygen intercalation to decouple graphene from Ru(0001) to form a p-doped layer. The study outlines a method to modify graphene and also reveals that vibrational spectra of an adsorbed NHC provide a highly sensitive method to probe and distinguish between different graphene-on-metal systems.