Metallic phase–free Zn-Al mixed oxide dual function materials enable high CO selectivity in reactive carbon capture from dilute CO2 streams

Reactive carbon capture (RCC), whereby a dual function material (DFM) captures dilute CO 2 and subsequently converts it within the same reactor, can address persistent cost concerns in carbon capture and utilization technology advancement. Many DFMs utilize costly precious metals (e.g., Pt or Ru) or oxidation-sensitive transition metals (e.g., Ni and Cu), the latter of which can hinder utilization of CO 2 sources containing O 2 and/or increase the H 2 demand for oxide-metal reduction cycles. We report a precious metal-free, K-modified Zn-Al mixed oxide (ZnAlO x ) DFM that exhibited 99 % selectivity to CO at temperatures more than 250 °C lower than conventional RCC-to-CO routes. While unmodified ZnAlO x catalysts were effective for RCC, K-modification was found to significantly increase CO 2 adsorption capacity, improve retention of adsorbed CO 2 through the reactive desorption step, and suppress the formation of unreactive spectator species during reactive desorption. These effects combined to improve CO yield (53 %) far beyond equilibrium-limited predictions for CO 2 -to-CO under conventional steady state reaction conditions (<1 %). The DFM also exhibited remarkable oxidative stability, with negligible performance loss over 25 RCC cycles using simulated flue gas with 5 % O 2 , demonstrating its promise as a robust, low-cost material to enable highly selective conversion of CO 2 to CO in a single unit operation. • Rational design of metallic-phase free ZnAlO x -based dual function materials for reactive carbon capture (RCC). • Best performing K/Zn 1 Al 2 DFM produces CO with 99 % selectivity under atmospheric pressure. • CO yield achieved from RCC surpasses thermodynamic equilibrium predictions. • In-situ IR revealed K modified CO 2 adsorption characteristic, facilitate CO 2 conversion suppress unreactive intermediates. • K/Zn 1 Al 2 maintains high and stable performance with co-fed O 2