Rational Design of Indium–Palladium Intermetallic Catalysts for Selective CO2 Hydrogenation to Methanol

Indium–palladium intermetallic catalysts have shown great potential for CO2 hydrogenation to methanol. A deep understanding of the synergistic relationship between various components is key to developing efficient indium–palladium intermetallic catalysts. Here, we rationally designed a series of catalysts with various In–Pd ratios and found that InPd(2:1)/m-ZrO2 demonstrated the highest reactivity (5.1 mmol/gcat/h), maintaining this performance even after 70 h of stability testing at 270 °C and 4 MPa. This impressive performance is attributed to the formation of a stable indium–palladium intermetallic compound with the chemical formula In3Pd2 which is close to the In2O3 phase during the reduction process. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations were further conducted to confirm that the formate path is more favorable for indium–palladium intermetallic catalysts. Adsorption energy calculations of reactants determine the roles of In3Pd2 and In2O3: In2O3 tends to adsorb and activate CO2, while In3Pd2 has an advantage for the dissociation of H2, which could compensate for the insufficient ability of In2O3, thereby promoting the hydrogenation of reaction intermediates. These findings highlight the crucial role of indium–palladium intermetallic compounds in selective CO2 hydrogenation to methanol.