In Situ DRIFTS and Modulation–Excitation Studies for CO₂ Hydrogenation on Nanostructures of CeO₂: Unraveling the Dynamic Nature of CO₂↔Hydroxylated-Ceria Interfaces

In transient or ME-PSD studies, performed with the exposure of the ceria nanostructures to CO₂/H₂ mixtures at 250 °C, hydrogen carbonates and formates were identified as dynamic species in adsorption/desorption processes that have a limited contribution to the RWGS reaction. On both catalytic surfaces, hydroxyl groups and carbonate adsorbates initially experienced a rapid, kinetically controlled reduction (OH_adsorbed + 0.5H_2,gas → O_vacancy + H₂O_gas) and oxidation (CO_3,ads + O_vacancy→ CO_gas + 2O_oxide) process that was part of the RWGS reaction.

The ceria nanocubes had an additional reaction pathway, where direct carbonate decomposition, involving the transformation of transient and surface tridentate carbonates, enhanced the RWGS rate. Overall, these results illustrate the tremendous impact that hydrogen can have on the adsorption and reaction of CO₂ with oxide surfaces and strongly emphasize the need to consider different oxide nanostructures to successfully optimize the performance of CeO₂-based catalysts for CO₂ hydrogenation.