Collaborative Research: SUSCHEM: Engineering Polymer-Nanocatalyst Membranes for Direct Capture of CO2 and Electrochemical Conversion to C2+ Liquid Fuel

由于二氧化碳等温室气体排放的增加，环境问题日益严重。控制二氧化碳水平的一种有效方法是直接捕获空气中的二氧化碳并将其转化为其他碳形式。使用空气作为原料将二氧化碳直接转化为可重复使用的碳产品是非常困难的，目前的方法通常涉及额外的能源密集型步骤，以生产纯二氧化碳作为随后催化转化的原料。该提案将解决当前未解决的挑战，以最小的能量输入捕获/释放直接捕获空气，并将二氧化碳顺序电还原为增值液体燃料。这个概念是基于一种新颖的生物启发过程的设计。核心组件是纤维素基膜，直接用于从空气中捕获和分离二氧化碳。这种新的捕获反应，以前还没有研究过，将为直接空气捕获二氧化碳提供一个非常强大的处理工具。为了将二氧化碳转化为可重复使用的碳，将研究一种地球上丰富的新型钴催化剂（六方紧密排列的钴纳米片）。通过纤维素-石墨烯-钴体系，合理控制局部碱度和CO2与催化剂的接近度，可以方便地实现捕集和转化，从而实现CO2的高效电还原。通过布朗大学和康涅狄格大学之间的合作努力，拟议的研究将产生一个一体化集成系统的创新设计，以实现可持续的二氧化碳捕获和利用。该提案旨在开发一种新的电化学系统，用于在环境条件下直接捕获空气并将二氧化碳转化为乙醇和/或乙醇。该系统由天然纤维素和沉积在石墨烯上的新型六方钴纳米片催化剂组成，提供了一个高导电性和多孔的聚合物网络，其中两个组件在直接空气捕获和二氧化碳电还原中协同工作。富含羟基的无定形纤维素可以在碱催化下以亚稳半碳酸盐的形式捕获二氧化碳。这些亚稳态半碳酸盐可以在pH值变化或温和加热时可逆地释放二氧化碳，为二氧化碳的捕获和释放提供了一种节能的方法，这是受光合作用中自然二氧化碳浓度机制的启发。释放的二氧化碳靠近组装在石墨烯上的钴纳米片催化剂，并集成到纤维素膜中，作为工作电极，将二氧化碳选择性电还原为C2产品。一个工作的流动电池系统将被证明是一个工程方法直接捕获和转换二氧化碳与空气为原料。该研究不仅将为纤维素加工方法提供新的设计概念，并为钴纳米片促进二氧化碳还原反应中的C-C偶联提供新的基础知识，而且还将为直接捕获和转化二氧化碳提供节能的工程解决方案。该项目的一部分将在布朗大学完成，由电化学系统项目和促进竞争研究的既定项目（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

There have been rising environmental concerns resulting from the increasing emission of greenhouse gasses like CO2. One effective way to manage CO2 level is to directly capture and convert CO2 from air to other carbon forms. The direct conversion of CO2 using air as feedstock to a reusable carbon product has been extremely difficult and current approaches often involve an additional energy-intensive step to produce pure CO2 as feedstock for subsequent catalytic conversion. This proposal will address the current unmet challenges to allow direct air capture with a minimum energy input on capture/release and sequential electroreduction of CO2 to value-added liquid fuels. The concept is based on the design of a novel bioinspired process. The central component is a cellulose-based membrane that is used directly for capture and separation of CO2 from air. This new capture reaction, not yet been studied previously, will provide a very powerful processing tool for direct air capture of CO2. To convert CO2 to a reusable form of carbon, a new class of earth-abundant cobalt catalyst (hexagonal close packed cobalt nanosheets) will be studied. The capture and conversion will be realized conveniently via the cellulose-graphene-cobalt system in which local basicity and CO2 proximity to the catalyst are rationally controlled to facilitate efficient electroreduction of CO2. Through collaborative efforts between Brown and UConn, the proposed studies will generate an innovative design of an all-in-one integrated system to realize sustainable CO2 capture and utilization.This proposal aims to develop a novel electrochemical system for direct air capture and conversion of CO2 to ethanal and/or ethanol under ambient conditions. The system consists of natural cellulose and a new hexagonal cobalt nanosheet catalyst deposited on graphene, providing a highly conductive and porous polymer network where the two components work cooperatively in direct air capture and electroreduction of CO2. Hydroxyl-rich amorphous cellulose can capture CO2 in the form of metastable hemi-carbonates catalyzed by a base. These metastable hemi-carbonates can reversibly release CO2 upon pH change or gentle heating, providing an energy-efficient approach to CO2 capture and release, which is inspired by natural CO2 concentration mechanisms in photosynthesis. The released CO2 is in proximity of the robust cobalt nanosheet catalyst assembled on graphene and integrated into the cellulose membrane, which functions as a working electrode to carry out the selective electroreduction of CO2 to C2 products. A working flow-cell system will be demonstrated as an engineering approach to direct capture and conversion of CO2 with air as feedstock. The study will offer not only a new design concept on cellulose processing method and new fundamental knowledge on the cobalt nanosheet-promoted C-C coupling in the CO2 reduction reaction, but also an energy-efficient engineering solution to direct CO2 capture and conversion.The portion of this project that will be completed at Brown University is jointly funded by the Electrochemical Systems Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.