Institute for Frontier Materials and ARC Centre of Excellence for Electromaterials Science, Deakin University, Waurn Ponds, 3216, Australia.
School of Chemistry, Monash University, Clayton, 3800, Australia.
J Am Chem Soc. 2022 Mar 9;144(9):3875-3891. doi: 10.1021/jacs.1c11545. Epub 2022 Feb 28.
From atomic force microscopy (AFM) experiments, we report a new phenomenon in which the dissolution rate of fused silica is enhanced by more than 5 orders of magnitude by simply pressing a second, dissimilar surface against it and oscillating the contact pressure at low kHz frequencies in deionized water. The silica dissolution rate enhancement was found to exhibit a strong dependence on the pressure oscillation frequency consistent with a resonance effect. This harmonic enhancement of the silica dissolution rate was only observed at asymmetric material interfaces (e.g., diamond on silica) with no evidence of dissolution rate enhancement observed at symmetric material interfaces (i.e., silica on silica) within the experimental time scales. The apparent requirement for interface dissimilarity, the results of analogous experiments performed in anhydrous dodecane, and the observation that the silica "dissolution pits" continue to grow in size under contact stresses well below the silica yield stress refute a mechanical deformation or chemo-mechanical origin to the observed phenomenon. Instead, the silica dissolution rate enhancement exhibits characteristics consistent with a previously described 'electrochemical pressure solution' mechanism, albeit, with greatly amplified kinetics. Using a framework of electrochemical pressure solution, an electrochemical model of mineral dissolution, and a recently proposed "surface resonance" theory, we present an electro-chemo-mechanical mechanism that explains how oscillating the contact pressure between dissimilar surfaces in water can amplify surface dissolution rates by many orders of magnitude. This reaction rate enhancement mechanism has implications not only for dissolution but also for potentially other reactions occurring at the solid-liquid interface, e.g. catalysis.
从原子力显微镜（AFM）实验中，我们报告了一种新现象，即在去离子水中以低 kHz 频率振荡接触压力时，只需将第二个不同的表面压在熔融二氧化硅上，就可以将其溶解速率提高 5 个数量级以上。发现二氧化硅的溶解速率增强与压力振荡频率有很强的依赖关系，与共振效应一致。这种二氧化硅溶解速率的谐波增强仅在不对称材料界面（例如，金刚石在二氧化硅上）中观察到，在实验时间范围内，在对称材料界面（即二氧化硅在二氧化硅上）上没有观察到溶解速率增强的迹象。界面非相似性的明显要求、在无水十二烷中进行的类似实验的结果以及观察到在低于二氧化硅屈服应力的接触应力下，二氧化硅“溶解坑”继续增大，这都驳斥了观察到的现象是机械变形或化学机械起源的观点。相反，二氧化硅溶解速率的增强表现出与先前描述的“电化学压力溶解”机制一致的特征，尽管动力学大大增强。使用电化学压力溶解的框架、矿物溶解的电化学模型和最近提出的“表面共振”理论，我们提出了一种电-化学-机械机制，解释了如何通过在水中振荡不同表面之间的接触压力，可以将表面溶解速率提高几个数量级。这种反应速率增强机制不仅对溶解而且对固-液界面上可能发生的其他反应（例如，催化）都有影响。
