Surface Chemistry at the Solid‐Solid Interface; Selectivity and Activity in Mechanochemical Reactions on Surfaces
Surface Chemistry at the Solid‐Solid Interface; Selectivity and Activity in Mechanochemical Reactions on Surfaces
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DOI：
10.1002/cmtd.202100052
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发表时间：
2021-07
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影响因子：
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通讯作者：
Resham Rana;Robert Bavisotto;Kaiming Hou;Nicholas C. Hopper;W. Tysoe
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作者：
Resham Rana;Robert Bavisotto;Kaiming Hou;Nicholas C. Hopper;W. Tysoe
本文总结了支撑施加在化学系统上的力可以加速其速率或诱导不能通过热进入的反应途径的方式的概念。1935年，Evans和Polanyi首先描述了这一点，他们利用过渡态理论的热力学分析证明了静水压力如何加速化学反应的速率，反应速率随压力呈指数增长，并取决于所谓的活化体积。这通常为~ 17 Å3/分子，表明需要GPa数量级的压力来加速化学反应的速率，化学反应通常发生在固体-固体界面，如在球磨机中发现的。我们描述了表面机械化学反应机制是如何用剪切诱导分解铜羧酸盐的例子来研究的。它们在加热到~ 650 K时热分解，产生二氧化碳并在表面沉积碳氢化合物，但剪切应力加快了这一过程的速度，因此它在室温下发生。然而，也发现平行于COO平面的力诱导了一个非热反应途径，在表面上进化出一氧化碳和吸附氧。这种反应途径可以通过吸附苯甲酸酯来淬灭，因为芳基环的面积越大，COO平面向表面的倾斜就越大，从而增加了热反应的速率。
This paper summarizes the concepts that underpin the way in which forces exerted on chemical systems can either accelerate their rates or induce reaction pathways that cannot be accessed thermally. This was first described in 1935 by Evans and Polanyi who showed how hydrostatic pressure could accelerate the rates of chemical reactions using a thermodynamic analysis of transition‐state theory to demonstrate that the reaction rate increased exponentially with pressure, and depends on a so‐called activation volume. This is typically ∼17 Å3/molecule and indicates that pressures on the order of GPa′s are required to accelerate the rates of chemical reactions, which commonly occur at solid‐solid interfaces such as found in a ball mill. We describe how surface mechanochemical reaction mechanisms are studied using the example of the shear‐induced decomposition of carboxylates on copper. They thermally decompose on heating to ∼650 K to evolve carbon dioxide and deposit a hydrocarbon on the surface but shear stresses accelerate the rate of this process so that it occurs at room temperature. However, it is also found that forces parallel to the COO plane induce a non‐thermal reaction pathway to evolve carbon monoxide and adsorbed oxygen on the surface. This reaction pathway can be quenched by using adsorbed benzoate species because the larger area of the aryl ring accentuates the tilt of the COO plane towards the surface to increase the rate of the thermal reaction.