Syngas Conversion to C₂ Oxygenates over the Cu/β-Mo₂C Catalyst: Probing into the Effect of the Interface between Cu and β‑Mo₂C on Catalytic Performance

Aiming at probing into the role of the interface between Cu and Mo₂C for syngas conversion to C₂ oxygenates over the Cu/β-Mo₂C catalyst, the formation mechanism of C₂ oxygenates from syngas over the Cu/β-Mo₂C catalyst has been systematically investigated using density functional theory calculations. The results show that the CH monomer is the most preferred CH_<i>x</i> species formed via the route of CO direct dissociation into C, followed by C hydrogenation to CH; moreover, the Cu/β-Mo₂C­(001) catalyst presents higher activity and selectivity toward CH formation instead of CH₃OH formation. For C₂ oxygenate formation, CHO insertion into CH to form the C₂ oxygenate CHCHO is the most preferred. Compared to the pure Cu(111) and β-Mo₂C­(001), Cu/β-Mo₂C­(001) exhibits better selectivity toward CH formation, and has the strong ability of C–C chain growth for C₂ oxygenate formation. On the other hand, the analysis of electronic and structural properties indicates that there is a strong charge transfer between Cu and Mo₂C to form a charge-rich region at the interface of the Cu/β-Mo₂C­(001) catalyst, which promotes the C–O bond cleavage of CO and CHO to form the CH monomer adsorbed at the interface, and favors the subsequent CHO insertion into CH to form the C₂ oxygenate CHCHO at the interface. As a result, the synergistic effect including the electronic and geometric effect that occurred at the interface between Cu and β-Mo₂C­(001) leads to high productivity toward C₂ oxygenates in syngas conversion over the Cu/β-Mo₂C­(001) catalyst.