PRESS RELEASE

Development of CO2-to-Methanol Hydrogenation Catalyst by Focusing on the Coordination Structure of the Cu Species in Spinel-Type Oxide Mg1–xCuxAl2O4

 

Authors

Shohei Tada, Fumito Otsuka, Kakeru Fujiwara, Constantinos Moularas, Yiannis Deligiannakis, Yuki Kinoshita, Sayaka Uchida, Tetsuo Honma, Masahiko Nishijima, Ryuji Kikuchi

Abstract
Dispersion of metallic Cu nanoparticles on a metal oxide support increases the number of exposed metallic Cu sites and/or Cu-support interfacial sites, resulting in good catalytic performance for CO2-to-methanol hydrogenation. However, the formation of highly dispersed Cu nanoparticles is challenging because they are easily sintered. Here, we studied Cu nanoparticle formation by a simple deposition–reduction technique using Cu-doped MgAl2O4 (Mg1–xCuxAl2O4). Mg1–xCuxAl2O4 possessed the following three types of Cu2+ species: short O–Cu octahedrally coordinated [CuO6]s, elongated O–Cu octahedrally coordinated [CuO6]el, and tetrahedrally coordinated [CuO4]t. The former two are found in the inverse-spinel-type Mg1–xCuxAl2O4, while the other is found in the normal-spinel-type Mg1–xCuxAl2O4. Additionally, by focusing on the difference in the reducibility of the Cu2+ species, we clarified that their fraction is related to Cu loading. For low Cu loading (x < 0.3), Mg1–xCuxAl2O4 mainly contained the [CuO6]s species. On the other hand, for high Cu loading (x ≥ 0.3), the fraction of the [CuO6]el and [CuO4]t species increased. Notably, among the prepared catalysts, H2-reduced Mg0.8Cu0.2Al2O4 (x = 0.2) had the largest number of exposed metallic Cu sites, resulting in its good catalytic performance. Hence, the H2 reduction of [CuO6]s is essential for forming metallic Cu nanoparticles on metal oxides.



ACS Catalysis : https://pubs.acs.org/doi/10.1021/acscatal.0c02868