Enhancing hydrogen spillover and oxygen vacancies in CdZrOx solid solution catalysts via the synergistic effect of Cu and Ga for efficient CO2 hydrogenation to methanol

Abstract

Solid solution catalysts have attracted considerable attention for the CO₂ hydrogenation to methanol reaction, owing to their high methanol selectivity and excellent long-term stability. However, the hydrogenation capacity of such catalysts is relatively weak, resulting in low methanol synthesis activity. Herein, we ingeniously constructed nCuGaCdZrO_x solid solution catalysts with dual H₂ activation sites of Cu and Ga. The 2CuGaCdZrO_x catalyst exhibits a CO₂ conversion of 6.1% and a methanol yield of 373 mg g_cat⁻¹ h⁻¹ at 320 °C. Compared with CdZrO_x, 5GaCdZrO_x and 2CuCdZrO_x, the methanol space-time yield is increased by 62.2%, 31.8% and 108.4% respectively. In-depth characterizations reveal that the improved performance is primarily ascribed to the synergistic effect between Cu and Ga sites. This synergistic effect significantly increases the oxygen vacancy density of the 2CuGaCdZrO_x catalyst, thereby enhancing the CO₂ adsorption and activation capacity, which encourages the formation of carbonate and bicarbonate species. Furthermore, both highly dispersed Cu and Ga play pivotal roles in promoting H₂ dissociation and activation, which further accelerates the conversion of carbon-containing intermediate species to methanol by the formate pathway. This study elucidates the mechanism of solid solution catalysts with synergistic dual active sites in the CO₂ hydrogenation to methanol reaction.