Exploring the sustained release catalysis of CuAl2O4 spinel for highly effective CO2 conversion to CO

Sustained Release Catalysis concept has been demonstrated over Cu-based spinel catalysts to retard Cu agglomeration via gradually releasing active copper from spinel lattice during catalytic reaction. Herein, the solid-phase synthesized stoichiometric CuAl2O4 spinel is illustrated to be an effective sustained release catalyst for CO2 hydrogenation to CO (RWGS). Characterizations point out a mechanism that active Cu can be liberated from spinel lattice under the RWGS atmosphere, forming Cu-deficiency defect spinel with abundant surface hydroxyl groups on rearranged spinel Al ions. Cu entities and surface hydroxyls can well activate H2 and CO2, producing monodentate and bidentate formate species as crucial intermediates for CO, especially, the monodentate formate located on spinel octahedral AlVI presents superior dissociation performance and contributes more to the CO formation. The successful application of the Sustained Release Catalysis concept in RWGS provides significant insight for understanding the catalytic dynamics of Cu-spinel catalysts in CO2 hydrogenation process.