The role of surface hydroxyls on ZnZrO solid solution catalyst in CO2 hydrogenation to methanol

ZnZrOx solid solution catalyst is an excellent catalyst in methanol synthesis from CO2 hydrogenation. It is still highly aspiration to make any further improvement in catalytic performance. In this work, ZnZrOx solid solution catalyst is prepared with different methods, resulting in different surface property. The ZnZrOx solid solution catalyst prepared by reflux ammonia (ZnZrOx-RA) exhibits higher methanol selectivity of 95.2% and CO2 conversion of 3.3% than that of the catalyst obtained via co-precipitation (ZnZrOx-CP) at 280 °C, 5 MPa. Subsequent kinetics analysis shows that ZnZrOx-RA, in comparison to ZnZrOx-CP, shows a decreased activation energy for methanol synthesis, an increased reaction order in H2, and a similar reaction order in CO2. Structural characterizations indicate that these two catalysts are in solid solution state, while ZnZrOx-RA possesses more Zn-OH species on the surface. The surface Zn-OH species enhance the activation and adsorption of CO2 and H2, and improve the generation and stability of HCOO* species, which promote CO2 hydrogenation to methanol.