The promoting role of Ga in ZnZrOx solid solution catalyst for CO2 hydrogenation to methanol

Abstract

Catalytic conversion of CO2 into methanol utilizing green hydrogen produced from renewable energy is a promising route to realize carbon neutrality. Although ZnZrOx solid solution catalyst displays excellent catalytic performance, it is still highly desired to make any further improvement. Herein, we found the promoting effect of incorporating Ga into ZnZrOx solid solution catalyst in CO2 hydrogenation to methanol. Ga promoted ZnZrOx (GaZnZrOx) solid solution catalyst exhibits CO2 conversion of 8.8% and methanol space time yield of 630 mg gcat−1 h−1 that are higher than those of ZnZrOx solid solution catalyst (7.7%, 556 mg gcat−1 h−1) at 320 °C, while the highly selectivity toward methanol remains unchanged. Chemisorption and H2-D2 exchange results show that GaZnZrOx solid solution catalyst displays higher capacity for the adsorption and activation of H2 than ZnZrOx solid solution catalyst. Electron paramagnetic resonance result suggests that more oxygen vacancies are derived after incorporating Ga into ZnZrOx solid solution catalyst. In situ diffuse reflectance infrared Fourier transform spectra indicate that the HCOO* and CH3O* species are the main intermediate species. The higher IR intensity of intermediate species and lower CH3O*/HCOO* ratio on GaZnZrOx solid solution catalyst suggest that the hydrogenation of HCOO* to CH3O* is boosted. These results reveal the promoting effect of incorporated Ga into ZnZrOx solid solution catalyst that improves the adsorption and activation of H2 and CO2, thus enhancing catalytic performance of methanol synthesis from CO2 hydrogenation.