Collaborative Research: Catalysis on crowded surfaces: the effects of co-adsorbates on CO and CO2 hydrogenation mechanisms

About This Grant

Converting hydrogen and carbon-containing feedstocks, such as CO and CO2, to synthetic fuels would augment US energy security and independence. Specifically, CO and CO2 hydrogenation are critical components in the industrial production of methanol, one of the most important platform chemicals in the chemical industry. Improving our understanding of these reactions will improve the competitiveness of the US chemical industry while potentially lowering energy and capital costs. These reactions rely on catalytic conversion processes that occur at low temperatures and high pressures. The high pressure drives the CO and CO2 molecules onto the metal catalyst surface, resulting in crowded surfaces, where molecular interactions among bound intermediates play a key role in changing the reaction dynamics and activating strong chemical bonds. This project will examine the mechanistic role of densely covered surfaces in mediating the various CO and CO2 hydrogenation reactions. The effort will focus on two benchmark systems: methanol synthesis on Cu-based catalysts and methanation on Ni-based catalysts. These systems will be probed with complementary kinetic, spectroscopic, isotopic, and computational studies examining the role of these extended catalytic microenvironments. Educational videos discussing scientific principles and methods in catalysis research broadcast over social media channels accessible to researchers of all backgrounds will provide training and broaden awareness of science and engineering principles involved in the production of fuels. This research is based on the premise that higher entropic demands of bimolecular reactions among bound surface intermediates on densely crowded surfaces are compensated by lower energy barriers for catalytic reactions on such surfaces. The research efforts are motivated by previous work, which showed the high pressure and low temperature conditions of methanol synthesis over Cu-based catalysts result in Cu surfaces highly covered with H-adatoms. Such high H-coverages provide novel routes for CO2 activation via molecular intermediates that are only stable on surfaces with high H-adatom coverage. The project will involve the systematic, intentional generation of high H-atom coverage microenvironments. Microenvironments will be controlled by changing pressures, temperatures, gas composition, titrants, and surface composition. Reversibility formalisms, spectroscopic methods, and density functional theory (DFT) calculations will be used to develop a kinetic framework to understand the reaction environments. The collaborative computational and experimental nature of this project will provide unique opportunities for interdisciplinary education and training of undergraduate and graduate students.. 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.