NSF Award
2324346
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.<br/><br/>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.<br/><br/>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).<br/><br/>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.
