Inducing High-Energy-Barrier Tribochemical Reaction Pathways; Acetic Acid Decomposition on Copper
Inducing High-Energy-Barrier Tribochemical Reaction Pathways; Acetic Acid Decomposition on Copper
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DOI：
10.1007/s11249-021-01407-z
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发表时间：
2021-02
影响因子：
3.2
通讯作者：
Resham Rana;Robert Bavisotto;Nicholas C. Hopper;W. Tysoe
中科院分区：
文献类型：
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作者：
Resham Rana;Robert Bavisotto;Nicholas C. Hopper;W. Tysoe
利用超高真空摩擦计研究了醋酸在铜表面的摩擦化学，并辅以第一性原理密度泛函理论计算了表面结构和反应途径。利用反射-吸收红外光谱法鉴定，在室温条件下，乙酸在桥位上形成η -乙酸。用碳化钨球摩擦表面，以相同的速率减少摩擦区域的碳和氧的数量，在表面留下一些碳和氧。这与热分解途径不同，在热分解途径中，加热到~ 580 K会去除所有的氧，但在表面留下少量的碳。据推测，这是因为沿着吸附的醋酸物质平面内的方向滑动可以诱导高能量势垒途径，其中η - 2-乙酸盐倾斜形成η - 1-乙酸盐，该η -乙酸盐可以反应形成弯曲的CO2δ−物质，分解出一氧化碳并在表面沉积原子氧。重复的醋酸加药和摩擦使表面能吸附的醋酸总量在4次循环后减少了50%，从而得到稳定的低摩擦膜。在这一点上，吸附的醋酸完全被摩擦化学去除。这表明，吸附的醋酸可以形成一种自愈膜，其中任何低摩擦膜的磨损都可以通过剪切引起的吸附醋酸物质的分解来补充。
The surface tribological chemistry of acetic acid on copper is studied using an ultrahigh vacuum tribometer, supplemented by first-principles density functional theory calculations of the surface structure and reaction pathways. Acetic acid forms η2-acetate species on bridge sites at room temperature as identified by reflection–absorption infrared spectroscopy. Rubbing the surface with a tungsten carbide ball reduces the amount of carbon and oxygen in the rubbed region at the same rates to leave some carbon and oxygen on the surface. This is different from the thermal decomposition pathway, where heating to ~ 580 K removes all oxygen, but leave a small amount of carbon on the surface. It is postulated that this arises because sliding along a direction aligned within the plane of the adsorbed acetate species can induce a high-energy-barrier pathway in which the η2-acetate tilts to form an η1-acetate that can react to form a bent CO2δ−species that decomposes to evolve carbon monoxide and deposit atomic oxygen on the surface. Repeated acetic acid dosing and rubbing reduces the total amount of acetic acid that can adsorb on the surface by ~ 50% after ~ 4 cycles, resulting is a stable, low-friction film. At this point, the adsorbed acetic acid is completely tribochemically removed. This suggests that adsorbed acetic acid can form a self-healing film in which any wear of the low-friction film will then allow it to be replenished by shear-induced decomposition of adsorbed acetate species.