RII Track-4: NSF: Inhibition of Catalytic Deactivation Mechanisms during CO2 Utilization

Louisiana State University, Baton Rouge LA

Investigators

Abstract

The ability to convert CO2 and methane into fuels can further enable the hydrogen economy. This ability can also promote US energy independence while limiting the emission of greenhouse gases. However, the controlled conversion of these gases into basic building block chemicals is currently performed at high temperatures, promoting the long-term degradation of the catalyst. This project aims to understand how deactivation pathways can be prevented using a nonreducible thin-film over-layer that confines surface species to active sites and limits unwanted reactions. Understanding these processes is fundamental to the development of new, catalysts with increased stability that can lower reaction temperatures and decrease overall energy consumption. Specifically, the PI will partner with Oak Ridge National Laboratory to observe the formation and movement of reacting surface molecules and the impact of these phenomena on the evolving catalyst structure and its degradation. Additionally, this NSF EPSCoR RII Track-4 fellowship project provides hands-on training in state-of-the-art characterization tools. The skills developed during this project will be used to enhance the current suite of tools at Louisiana State University to probe other industrially relevant reactions that are important to the regional economy. Utilizing CO2-based feedstocks impacts numerous industrially relevant chemical processes, such as dry reforming of methane. To maximize conversion, catalysts are engineered for high surface areas and metal site dispersions. However, the reaction conditions needed to overcome thermodynamic equilibrium limitations result in the instability of catalyst structures prone to coking and undesirable side reactions. The mechanisms behind metal ripening and their subsequent effects are poorly understood, and in some studies, large changes in metal dispersion can have little effect on catalyst performance. The PI hypothesizes that metal clusters deposited on a catalyst substrate can be stabilized using a porous, nonreducible thin film to limit metal surface diffusion and growth and adsorbate spillover. Limiting substrate/metal ripening reduces coke-derived deactivation and maintains high metal dispersions responsible for the catalytic activity. This hypothesis is based on recent literature, which shows that porous shell layers can withstand ripening at some conditions. The proposed work will be performed in collaboration with Oak Ridge National Lab (ORNL), leveraging their in-operando characterization techniques and high-resolution aberration-corrected electron microscopes. Access to these unique capabilities will facilitate hands-on training with a superior electron microscope in preparation for LSU’s acquisitions of STEM, operando infrared, and chemisorption analyzers vital in understanding surface chemistry. This experience will strengthen the PIs research profile, specifically in the area of operando surface chemistry, and enable the study of other energy-intensive industrially relevant reactions. 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.