Characterization of CO2 Binding on Alkaline Metal Oxide Sorbents and DFMs for Combined Capture and Conversion
As the world endures environmental crises associated with climate change and the rise of atmospheric CO2 concentrations from anthropogenic CO2 emission, carbon capture and utilization (CCU) technologies are increasingly necessary. Reactive carbon capture (RCC) technologies, in which capture and conversion of CO2 occur in a single reactor, are more energetically and economically attractive by avoiding the need to purify, compress, and transport the captured CO2. To this end, the development of dual function materials (DFM) that enable CO2 capture and conversion to useful C1 products, namely (1) methane, (2) CO, and (3) methanol, are attractive near-term targets for commercial CCU processes for renewable fuels and chemicals. DFM are composed of sorbents and catalysts co-dispersed on the same high surface area carrier. The sorbent component allows for selective capture of CO2 from a gas stream and the catalyst component subsequently performs the in-situ conversion of the adsorbed CO2 upon introduction of a reactive gas (typically H2). The survey of DFM formulations reveals a variety of sorbent+catalyst combinations of interest. There is, however, a lack of depth in fundamental understanding of how the CO2 binds to these materials and how the subsequent reaction mechanisms are affected, which are critical features for the development of next-generation materials with improved performance. To this end, we will describe in this work the CO2 binding characteristics of established and/or new DFM and their sorbent-only counterparts. The surface CO2 binding mechanism and capture capacity will be probed using techniques such as in-situ DRIFTS, operando TGA, and CO2 chemisorption.