Exploring the nature of copper species: CeO2 support shape effect and its influence on CO2 hydrogenation to methanol

• The catalytic performance of CuO/hydrangea-like CeO 2 is higher than that of others. • CuO/hydrangea-like CeO 2 enhances the dispersion of copper species. • CuO/hydrangea-like CeO 2 is beneficial to form oxygen vacancies and hydroxyl groups . • 4. Both m-HCOO* and bi-HCOO* are active intermediate species for CO 2 hydrogenation to CH 3 OH. A series of CuO catalysts supported on CeO 2 with different morphologies (nanorod, nanocube and hydrangea-like) were tested for the CO 2 hydrogenation into methanol. Remarkable morphology-dependent CuO-CeO 2 interaction was observed, which was associated with the types and concentrations of copper species. The best performance was obtained over the CuO/hydrangea-like-CeO 2 catalyst, giving CO 2 conversion of 15.6 % and methanol selectivity of 92.4 % at 260 °C and 3 MPa. The enhanced activity was due to the largest amount of small particle size of copper species, which was responsible for the facile activation of H 2 . Additionally, the Cu 2+ -O v -Ce x species facilitated the generation of oxygen vacancies and hydroxyl groups, these two species favored formate production and further hydrogenation to methanol. Moreover, in situ diffuse reflectance infrared fourier transform spectroscopy ( in situ DRIFTS) results revealed that the both monodentate formate (m-HCOO*) and bidentate formate (bi-HCOO*) were key and necessary intermediate of CO 2 hydrogenation to methanol. The proposed predominate reaction pathway was m-HCOO*→ b-*OCH 3 → CH 3 OH and the minor one was bi-HCOO* → t-*OCH 3 → CH 3 OH.