Initiation of Vacancy-Mediated, Surface Explosion Reactions: Tartaric and Aspartic Acid on Cu Surfaces
Initiation of Vacancy-Mediated, Surface Explosion Reactions: Tartaric and Aspartic Acid on Cu Surfaces
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DOI：
10.1021/acs.jpcc.9b03895
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发表时间：
2019-08-08
影响因子：
3.7
通讯作者：
Gellman, Andrew J.
中科院分区：
文献类型：
--
作者：
Kondratyuk, Petro;Karagoz, Burcu;Gellman, Andrew J.
表面爆炸反应具有高度非线性的反应动力学，在等温条件下表现出自动加速。这些可以导致诸如振荡表面反应速率和手性吸附物在手性表面上的高度对映体特异性反应的现象。酒石酸（TA）在Cu表面上通过爆炸机制分解，该机制通过在TA分解期间自催化地自我复制的空位、空吸附位点传播。表面爆炸动力学的结果从链分支步骤，其中一个空位分解吸附产生两个空位。在没有空位的情况下，表面爆炸不会发生;它们需要一些产生空位的初始步骤。通过与链支化爆炸步骤的比较，很少有人知道的过程，引发或核表面爆炸反应。时间分辨XPS测量在爆炸引发的TA/Cu（hkl）的早期阶段揭示了一个过程，涉及TA从表面直接损失，以创建初始空位。在存在到表面的气相通量的情况下，这样的空位核可以被重新填充以抑制爆炸的开始。18个不同的Cu（hkl）表面取向的测量表明，引发过程的动力学结构不敏感。这意味着在手性Cu（hkl）表面上观察到的高度对映体特异性的TA分解动力学必须来自于链支化爆炸动力学的结构敏感性。
Surface explosion reactions have highly nonlinear reaction kinetics that exhibit autoacceleration under isothermal conditions. These can lead to phenomena such as oscillatory surface reaction rates and to highly enantiospecific reactions of chiral adsorbates on chiral surfaces. Tartaric acid (TA) decomposes on Cu surfaces by an explosion mechanism that is propagated by vacancies, empty adsorption sites that self-replicate autocatalytically during TA decomposition. Surface explosion kinetics result from chain-branching steps in which one vacancy decomposes an adsorbate to yield two vacancies. In the absence of vacancies, surface explosions cannot occur; they require some initiation step that creates vacancies. By comparison with the chain-branching explosion step, little is known about the processes that initiate or nucleate surface explosion reactions. Time-resolved XPS measurements during the early stages of explosion initiation of TA/Cu(hkl) reveal a process that involves direct loss of TA from the surface to create the initial vacancies. In the presence of a gas phase flux to the surface, such vacancy nuclei can be repopulated to suppress the onset of explosion. Measurements on 18 different Cu(hkl) surface orientations demonstrate that the kinetics of the initiation process are structure-insensitive. This implies that the highly enantiospecific TA decomposition kinetics observed on chiral Cu(hkl) surfaces must arise from the structure sensitivity of the chain-branching explosion kinetics.