Long-Range Metal-Sorbent Interactions Determine CO Capture and Conversion in Dual-Function Materials.

Carbon capture and utilization involve multiple energy- and cost-intensive steps. Dual-function materials (DFMs) can reduce these demands by coupling CO adsorption and conversion into a single material with two functionalities: a sorbent phase and a metal for catalytic CO conversion. The role of metal catalysts in the conversion process seems salient from previous work, but the underlying mechanisms remain elusive and deserve deeper investigation to achieve maximum utilization of the two phases. Here, preformed colloidal Ru nanoparticles were deposited onto a "NaO"/AlO sorbent to prepare prototypical DFMs with controlled phases for CO capture and hydrogenation to CH. Ru addition was found to double the high-temperature CO adsorption capacity by activating the "NaO"/AlO sorbent phase during a reductive pretreatment step. Most importantly, low Ru loadings were sufficient to ensure maximum CO adsorption and conversion. This was attributed to the key role of the metal-sorbent interactions, wherein Ru was required to hydrogenate strongly bound CO on the "NaO"/AlO sorbent to CH via the H activated on Ru. This interaction facilitated rate-determining carbonate migration and subsequent hydrogenation at the metal-sorbent interface. Overall, Ru controlled the CO hydrogenation reaction rate, while the "NaO"/AlO sorbent dictated the CO 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 CO capture and conversion efficiency.