CAREER: Combining Electrode Engineering with Electrochemical Modeling to Enable Atmospheric CO2 Capture

直接从大气中捕获二氧化碳是缓解气候变化的一种潜在方法。然而，由于二氧化碳浓度低(400ppm)，从空气中快速分离和提纯二氧化碳可能非常耗能。高能效二氧化碳捕获技术的开发将增强捕获二氧化碳并将其转化为有用的化学品和产品的可持续性、可负担性和商业吸引力。大多数现有的二氧化碳捕获技术都是靠热能运行的，这通常需要燃烧化石燃料。基于热量的二氧化碳捕集方法在利用热量进行分离工作时，也面临着基本的转换效率限制。相比之下，使用电能而不是热能捕获二氧化碳是有吸引力的，因为它不面临这一效率限制。此外，它可以使用可再生能源转换技术来运行，这种技术越来越容易获得，而且成本很低。该项目将开发一种新的节能二氧化碳分离方法，使用附着在碳电极上的电活性有机分子。在水溶液中极化这些电极会导致溶液的pH值发生可逆变化，从而实现二氧化碳分离。在碱性条件下，二氧化碳会以碳酸盐离子的形式被选择性地吸收，然后在酸性条件下以纯气体的形式释放出来。实验和建模技术将被用来理解电极的化学成分及其集成到电化学流动电池中如何影响整个分离过程的速度和能效。此外，该项目将使密歇根州居民参与非正式讨论和实际操作的科学演示，强调二氧化碳捕获和利用技术的必要性和好处。在界面工程和电化学系统计划的支持下，该项目旨在推进一种新的方法，使用化学功能化的有机部分碳电极，用于节能的电化学二氧化碳分离。在极化时，这些电极既可以从溶液中吸收质子，也可以将它们释放到溶液中，从而改变溶液的pH值，从而提供一种反应捕获和释放二氧化碳的机制。这些电极能够实现的pH变化的幅度和可逆性是控制分离过程能量效率的关键因素。这些因素强烈地依赖于有机部分在电极/电解液界面经历的电场强度。电分析和高分辨率X射线光谱技术的结合将被用来发展对质子转移的机理的理解，因为它的部分化学和在碳上的安装方式不同。这一知识将被用来设计电极，当部署在水基电化学流动电池中时，这些电极将从空气中浓缩二氧化碳。流动池测量将用于验证分离过程的基于物理的模型；该模型将提供对热力学和动能损失如何决定给定分离吞吐量的总能量输入和效率的理解。该教育计划通过基于发现的学习、非正式讨论、有针对性的动手演示和研究展览，在社区和研究人员之间提供面对面的交流，从而使公众接触到二氧化碳缓解技术的好处。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The capture of carbon dioxide (CO2) directly from the atmosphere is emerging as a potential approach to climate change mitigation. However, the rapid separation and purification of CO2 from air can be very energy-intensive because of its low concentration (400 ppm). The development of highly energy-efficient CO2 capture technology will enhance the sustainability, affordability, and commercial appeal of capturing CO2 and converting it into useful chemicals and products. Most incumbent CO2 capture technologies run on heat, which typically requires burning fossil fuels. Heat-based CO2 capture methods also face a fundamental conversion efficiency limit in using heat for the work of separation. In contrast, CO2 capture using electrical rather than thermal energy is attractive because it does not face this efficiency limit. Moreover, it could be run using renewable energy conversion technology, which is increasingly available and inexpensive. This project will develop a new approach to energy-efficient CO2 separation that uses electro-active organic molecules attached to carbon electrodes. Polarizing these electrodes in an aqueous solution causes reversible changes in the pH of the solution, which enables CO2 separation. CO2 will be selectively absorbed in the form of carbonate ions under alkaline conditions and then released as a pure gas under acidic conditions. Experimental and modeling techniques will be used to understand how both the chemical composition of the electrode and its integration into an electrochemical flow cell influence the rate and energy efficiency of the overall separation process. Further, this project will engage Michigan residents in informal discussions and hands-on scientific demonstrations highlighting the need for and benefits of CO2 capture and utilization technology. With support from both the Interfacial Engineering and Electrochemical Systems programs, this project aims to advance a new way of using carbon electrodes, chemically functionalized with organic moieties, for energy-efficient electrochemical CO2 separation. Upon electric polarization, these electrodes can either absorb protons from or release them into solution, changing its pH, and thereby providing a mechanism for reactive CO2 capture and release. The extent and reversibility of pH changes that these electrodes can achieve are key factors controlling the energy efficiency of the separation process. These factors strongly depend on the strength of the electric field that the organic moiety experiences at the electrode/electrolyte interface. A combination of electroanalytical and in operando high-resolution x-ray spectroscopic techniques will be used to develop a mechanistic understanding of proton transfer as the chemistry of the moiety and manner of its installation on carbon vary. This knowledge will be exploited to engineer electrodes that will concentrate CO2 from the air when deployed in an aqueous electrochemical flow cell. Flow cell measurements will be used to validate a physics-based model for the separation process; the model will offer an understanding of how thermodynamic and kinetic losses dictate the overall energy input and efficiency for a given separation throughput. The education plan generates public exposure to the benefits of CO2 mitigation technology by offering face-to-face exchange between the community and researchers through discovery-based learning, informal discussion, targeted hands-on demonstrations, and a research exhibit.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.