(51b) Long-Range Metal-Sorbent Interactions Determine CO2 Adsorption and Conversion in Dual-Function Materials

Carbon capture and utilization involves multiple energy and cost-intensive steps. Dual-function materials (DFMs) can reduce these demands by coupling CO₂ adsorption and conversion into a single material with two functionalities: a sorbent phase, and a metal for catalytic CO₂ conversion. The role of metal catalysts in the conversion process seems salient from previous work, but the underlying mechanisms remain elusive and deserve a deeper investigation to achieve maximum utilization of the two phases.

In this talk, I will share the results of our recent work on using colloidal catalysts to understand sorbent-catalytic phase interactions in dual-function materials. First, pre-formed colloidal Ru nanoparticles were deposited onto a ‘NaO_x’/Al₂O₃ sorbent to prepare prototypical DFMs with controlled phases for CO₂ capture and hydrogenation to CH₄. Ru addition was found to double the high-temperature CO₂ adsorption capacity by activating the ‘NaO_x’/Al₂O₃ sorbent phase during a reductive pre-treatment step. Most importantly, low Ru loadings were sufficient to ensure maximum CO₂ adsorption and conversion. This was attributed to the key role of the metal-sorbent interactions, wherein Ru was required to hydrogenate strongly bound CO₂ on the ‘NaO_x’/Al₂O₃ sorbent to CH₄ via the H₂ activated on Ru. This interaction facilitated the rate-determining carbonate migration and its subsequent hydrogenation at the metal-sorbent interface. Overall, Ru controlled the CO₂ hydrogenation reaction rate, while the ‘NaO_x’/Al₂O₃ sorbent dictated the CO₂ uptake capacity. By controlling metal–sorbent interactions at the molecular level, we demonstrate the critical role of the two phases and their synergy, facilitating the design of DFMs with maximum CO₂ capture and conversion efficiency.