Selective phase transformation of layered double hydroxides into mixed metal oxides for catalytic CO oxidation

Phase transformation from layered double hydroxides (LDHs) into mixed metal oxides (MMOs) has been widely used in various catalytic applications owing to its numerous advantages over conventional synthesis methods. Herein we report the results of selective phase transformation of LDHs into spinels and delafossites for the preparation of phase-pure MMO catalysts. Pure cuprous delafossites and cupric spinels were selectively obtained through heat treatment of Cu-based LDHs followed by post-treatments. This enabled the study of the crystalline-phase-dependent CO oxidation activity of the MMO catalysts and their physicochemical properties. The spinel catalysts exhibited higher CO oxidation activities, in comparison with those of the delafossites, with greater redox properties and improved active sites for CO adsorption. Although the crystalline phases were derived from the same LDH precursors, the catalytic properties of the end product were greatly influenced by their crystal structures.