Understanding the structure of Cu-doped MgAl2O4 for CO2 hydrogenation catalyst precursor using experimental and computational approaches

Oxide Solid–Solution Catalysts with Good Redox Properties for Liquid–Phase Aerobic Additive–Free Oxidation: A Review

“…Furthermore, oxide solid solutions can be tailored for specific reactions by modulating the type and amount of transition–metal dopant. In addition to Cu–doped tetragonal ZrO 2 , [34] we have developed various oxide solid solutions, including Cu–doped MgAl 2 O 4 , [21,36,58] Ni–doped CeO 2 , [25] Zn–doped ZrO 2 , [8c] Cu–doped amorphous ZrO 2 , [8d,26] CuFe 2 O 4 , [58] and Rh–doped LaCrO 3 [5b] . The significant advantage associated with employing an oxide solid solution as a catalyst lies with catalyst–preparation simplicity; all that is required is an electric furnace and crucible, which makes this chemistry accessible even to those without specialized knowledge.…”

“…Additionally, DFT calculations can directly measure the charge state in addition to the structure. For example, Joutsuka et al revealed that three different Cu species are formed when the MgAl 2 O 4 spinel oxide is doped with Cu 2 + ; [36] these species contract octahedral [CuO 6 ] s (Figure 11a), elongated octahedral [CuO 6 ] el , and tetrahedral [CuO 4 ] t coordinations (Figure 11b). The former two have inverse spinel structures (Figure 4b), whereas the latter has a normal spinel structure (Figure 4a).…”

“…(Figure 12a-d ] t clusters also shown. [36] These images were drawn by VESTA. [13] The black lines indicate supercell boundaries.…”

“…[56] While discussions have ensued regarding the identity of highly dispersed Cu 2 + , X-ray absorption spectroscopy (XAS), DFT, and other methods have revealed that it is a square-planar [CuO 4 ] cluster on the t-ZrO 2 surface (Figure 13e). [36] The atomic radial distributions provided by XANES are unable to distinguish between tetrahedral and square-planar structures; hence, DFT calculations were used to determine the coordination structure. [34] These calculations also revealed the structure of the Ph-imidazole-CuO 2 intermediate shown in Figures 24a and 24 b, which is formed through transmetalation from [CuO 4 ].…”

Heterogeneous Cu Catalyst for CO₂-to-Methanol Hydrogenation Importance of Catalyst Precursor Structure

“…We also checked the coordination structure using the crystal model (Fig. 14) 29) . Importantly, [CuO6]s was formed only with low Cu content, so is related to the α peak in Fig.…”