Water-induced structural evolution of oxide catalysts is a key issue in heterogeneous catalysis, as it strongly affects catalyst active states, stability, and reaction pathways. However, the atomic-scale understanding of how water drives structural reconstruction in oxide catalysts remains unclear.
Recently, a research group led by Prof. FU Qiang and Prof. MU Rentao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) uncovered the water-induced dynamic structural evolution of oxides. The team revealed, at the atomic scale, the dynamic mechanisms of oxidative and reductive hydroxylation of cobalt-based oxides (CoOx) nanostructures in water vapor.
This study was published in the National Science Review.
Schematic of reductive and oxidative hydroxylation of CoOx nanostructures in H2O atmosphere (Image by Sun Xiaoyuan)
The researchers found that CoOx nanostructures with different initial structures follow distinct hydroxylation pathways in the presence of water. For CoO, water dissociatively adsorbs on the surface, driving its conversion into Co(OH)2, accompanied by oxidation of Co ions. In contrast, for CoO2−x surfaces containing both CoO and CoO2 domains, water first reacts with CoO domains, converting CoO into Co(OH)2, and forming a Co(OH)2–CoO2−x interface. Subsequent reaction with water at this interface promotes lattice oxygen removal, thereby inducing the reduction and hydroxylation of CoO2 domains and ultimately leading to full conversion into Co(OH)2.
"This work reveals the structural transformation mechanism by which water molecules play both oxidative and reductive roles on different CoOx structures, providing important insight into the role of water in oxide catalysis," said Prof. FU.