Improving Conversion of Captured CO2 on Mixed-Oxide Dual-Function Materials by Low-Concentration Metal Promotion

Reactive carbon capture (RCC) is a promising nascent approach to harness the untapped resource of waste CO2 to produce fuels and platform chemicals. However, process economics relies on the design of dual-function materials (DFMs) that exhibit maximal conversion of captured CO2 and high selectivity toward valuable carbon products (e.g., CO). Herein, we report the use of low-concentration (ca. 0.5 wt %) metal promotors (Pt and Au) to improve the conversion of captured CO2 on a Zn-Al mixed-oxide DFM by >30%, while also more than doubling per-cycle CO yield due to enhanced retention of captured CO2 and H2 activation. In situ DRIFTS of bound CO2 on the DFMs showed distinctions in surface carbonate formation for the Pt- and Au-modified materials that were correlated with product evolution during the reactive desorption step of RCC. Particularly, Pt afforded superior H2 activation but formed irreversibly-bound bicarbonates, compromising overall productivity, while the Na/Au/ZA DFM predominantly adsorbed CO2 on Na sites, resulting in polydentate carbonates that are retained until higher temperatures before conversion to CO. These results indicate that adding a low concentration of oxidation-resistant noble metals, especially Au, is an effective strategy for improving key performance metrics of Zn-Al mixed-oxide DFMs to further advance the development of scalable RCC technologies.. Authors: Hill, Alexander [National Laboratory of the Rockies, Golden, CO (United States)]; Jeong-Potter, Chae [National Laboratory of the Rockies, Golden, CO (United States)]; McNeary, W. Wilson [National Laboratory of the Rockies, Golden, CO (United States)] (ORCID:0000000183395121); Klinger, Anna [University of Michigan-Ann Arbor]; Arellano-Trevino, Martha [National Laboratory of the Rockies, Golden, CO (United States)] (ORCID:0000000292261843). DOE Contract: AC36-08GO28308. Subjects: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 42 ENGINEERING; CO2 hydrogenation; integrated carbon capture and conversion; metallic promoters; reactive carbon capture