A dual-site Cu-ZnO/Cu@Si catalyst boosts CO2 hydrogenation to CH3OH

Abstract

Cu-ZnO based catalysts are widely used for CO2 hydrogenation, but the CH3OH selectivity still needs to be improved. In this paper, dual-site Cu-ZnO/Cu@Si catalysts with Cu-O-Si structure and Cu-ZnO interface were prepared, and the 10Cu-ZnO/Cu@12Si sample exhibits optimal catalytic performance with the methanol selectivity and space-time yield of 70.6 % and 6.7 mmolMeOH·gcat−1·h−1 at 260 °C and 3 MPa, far exceeding those of the conventional Cu-ZnO/SiO2 (7.0 % for methanol selectivity and 1.22 mmolMeOH·gcat−1·h−1 for STYMeOH). The Cu-O-Si active site in Cu@Si is beneficial to the methanol synthesis and DFT calculations demonstrate the hydrogenation process follows the formate pathway. The Cu-ZnO interface can further convert CO generated at the Cu-O-Si active site to methanol. This synergistic effect is the main reason for the good catalytic performance of the dual-site samples. In-situ DRIFTS results also give evidence that *HCOO can be effectively hydrogenated to form *CH3O and the less gaseous CO exists on 10Cu-ZnO/Cu@12Si.