Boundary Conditions for Promotion versus Poisoning in Copper-Gallium-based CO2–to–Methanol Hydrogenation Catalysts

To establish descriptors for the activity of Cu-Ga-based CO2-to-methanol hydrogenation catalysts, we prepared via co-grafting followed by a reduction in hydrogen, a series of materials containing 3-6 nm Cu1-xGax alloyed nanoparticles with variable xGa. They display a volcano-type activity behavior, where methanol formation is promoted for xGa < 0.13, while above poisoning effects are observed. In catalysts that are prepared via different methods and differ in the degree of Ga reduction, only the fraction of Ga0 in the formed Cu-Ga alloy matters for the catalytic activity. We were therefore able to establish that the concentration of Ga0 in the Cu-Ga alloyed precatalyst is the main descriptor of methanol formation activity.