Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
ACS Appl Mater Interfaces. 2023 Apr 19;15(15):19634-19645. doi: 10.1021/acsami.3c00719. Epub 2023 Mar 21.
As fossil fuels remain a major source of energy throughout the world, developing efficient negative emission technologies, such as direct air capture (DAC), which remove carbon dioxide (CO) from the air, becomes critical for mitigating climate change. Although all DAC processes involve CO transport from air into a sorbent/solvent, through an air-solid or air-liquid interface, the fundamental roles the interfaces play in DAC remain poorly understood. Herein, we study the interfacial behavior of amino acid (AA) solvents used in DAC through a combination of vibrational sum frequency generation spectroscopy and molecular dynamics simulations. This study revealed that the absorption of atmospheric CO has antagonistic effects on subsequent capture events that are driven by changes in bulk pH and specific ion effects that feedback on surface organization and interactions. Among the three AAs (leucine, valine, and phenylalanine) studied, we identify and separate behaviors from CO loading, chemical changes, variations in pH, and specific ion effects that tune structural and chemical degrees of freedom at the air-aqueous interface. The fundamental mechanistic findings described here are anticipated to enable new approaches to DAC based on exploiting interfaces as a tool to address climate change.
由于化石燃料仍是全球主要的能源来源，开发高效的负排放技术（如直接空气捕集（DAC））变得至关重要，因为该技术可以从大气中去除二氧化碳（CO），从而减缓气候变化。尽管所有 DAC 工艺都涉及到 CO 通过气固或气液界面从空气中传输到吸附剂/溶剂中，但界面在 DAC 中的基本作用仍未得到充分理解。在此，我们通过振动和频发生光谱学和分子动力学模拟相结合的方法研究了 DAC 中使用的氨基酸（AA）溶剂的界面行为。这项研究揭示了大气 CO 的吸收对后续的捕获事件具有拮抗作用，这些捕获事件是由 bulk pH 的变化和反馈到表面组织和相互作用的特定离子效应驱动的。在所研究的三种氨基酸（亮氨酸、缬氨酸和苯丙氨酸）中，我们确定并分离了 CO 负载、化学变化、pH 值变化和特定离子效应的行为，这些行为调节了气液界面处的结构和化学自由度。预计这里描述的基本机制研究结果将为基于利用界面作为解决气候变化的工具的 DAC 提供新的方法。
