Origin of Room Temperature Methanol Synthesis over Hcp-PdMo.

The hydrogenation of CO2 to methanol has garnered significant interest with respect to the reduction of carbon emissions; however, the high temperatures and pressures typically required diminish the benefits of this approach. In this study, we report a hexagonal close-packed (hcp)-PdMo catalyst that exhibits the highest room temperature catalytic activity for CO2 hydrogenation to methanol among reported catalysts, with 100% methanol selectivity and without any signs of deactivation. Structural analyses, which included various in situ and ex situ X-ray techniques and infrared spectroscopy, have revealed that Mo and Pd serve as the active sites for CO2 adsorption and H2 dissociation, respectively. The CO2 hydrogenation reaction is facilitated at room temperature on the surface of the hcp-PdMo intermetallic catalyst, where the adjacently arranged Pd and Mo sites play important roles in methanol synthesis. Mechanistic studies, combined with density functional theory (DFT) calculations, have demonstrated that the reaction proceeds via a reverse water-gas shift and subsequent CO hydrogenation (R&C) pathway though a Pd-assisted Mo redox mechanism at room temperature. These findings not only reveal the origin of the reaction mechanism for methanol synthesis but also open a new direction for the design of highly efficient catalysts that function under mild conditions.