Goal 1
Understand and integrate multi-component systems of coupled microenvironments , tailoring molecules and materials for achieving targeted functionality in transport and activity around the active site.
The State of the Art in 2020: Many different physical and chemical processes need to work together in a unified system in order to convert solar energy into chemical energy. The current method to build such a system is to connect components that have been separately optimized – catalytic electrodes and light absorbers such as semiconductors – and provide an electrolyte in contact with them that allows ions to move between the electrodes. The final assembly’s geometry is set up to maximize efficiency by minimizing the resistances between the components that exchange charge. When such a system uses sunlight to convert CO₂ to reduced fuel products, carbon-carbon bond formation to generate liquid fuel products results in a mixture of C₂ and C₃ products. There is no clear path to improvement of these systems to form selectively just one product, or highly reduced products with 4 or more carbons in them.
LiSA’s Research: LiSA will overcome this limitation by using molecularly tailored chemical environments at and around catalysts and their interfaces to steer the chemistry toward formation of the desired liquid fuel product. This requires control over capture and release of species from the environment, electrocatalytic redox events involving them, and the detailed behavior of reaction intermediates at the catalytic center and in the electrolyte. Our focus is on controlling the delivery and availability of protons and water as well as electrons to obtain highly reduced products starting from CO₂ and N₂. These microenvironments will be assembled into complete systems designed to efficiently absorb light and produce liquid fuels. The systems will enable control over transport of key species between the microenvironments. In addition to demonstrating that this approach works, LiSA will address an important underlying science question: What are the foundational co-design principles for smart assembly of multi-component microenvironments to achieve collective functionality? To this end, we will establish a co-design process to create systems of microenvironment assemblies that dramatically expand the scope of optical, electronic and ionic transport and reaction processes that can be combined in a single liquid solar fuels system. A co-design approach that balances requirements for performance in coupled microenvironments is key to achieving systems that are at once selective, efficient and durable.
Team Contributions: LiSA’s Systems and Integration Team leads the system co-design process, and the Chemical Microenvironments Team leads co-design of the microenvironments for photoactivity and tunable mass transport. The Photodynamics team uses spatially resolved probes to map local proton and hydroxide concentrations. The Durability team evaluates how the microenvironments and their assemblies evolve during operation under real-world conditions, and how they can be stabilized to maintain their performance. The Photoactive Materials Team designs photocatalysts for the microenvironments that control the energy landscape of the reduction reactions in space and time.
Artwork: Darius Siwek