Rational Design\nof Indium–Palladium Intermetallic\nCatalysts for Selective CO<sub>2</sub> Hydrogenation to Methanol

Indium–palladium intermetallic catalysts have\nshown great\npotential for CO<sub>2</sub> hydrogenation to methanol. A deep understanding\nof the synergistic relationship between various components is key\nto developing efficient indium–palladium intermetallic catalysts.\nHere, we rationally designed a series of catalysts with various In–Pd\nratios and found that InPd(2:1)/m-ZrO<sub>2</sub> demonstrated the\nhighest reactivity (5.1 mmol/g<sub>cat</sub>/h), maintaining this\nperformance even after 70 h of stability testing at 270 °C and\n4 MPa. This impressive performance is attributed to the formation\nof a stable indium–palladium intermetallic compound with the\nchemical formula In<sub>3</sub>Pd<sub>2</sub> which is close to the\nIn<sub>2</sub>O<sub>3</sub> phase during the reduction process. In\nsitu diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)\nand density functional theory (DFT) calculations were further conducted\nto confirm that the formate path is more favorable for indium–palladium\nintermetallic catalysts. Adsorption energy calculations of reactants\ndetermine the roles of In<sub>3</sub>Pd<sub>2</sub> and In<sub>2</sub>O<sub>3</sub>: In<sub>2</sub>O<sub>3</sub> tends to adsorb and activate\nCO<sub>2</sub>, while In<sub>3</sub>Pd<sub>2</sub> has an advantage\nfor the dissociation of H<sub>2</sub>, which could compensate for\nthe insufficient ability of In<sub>2</sub>O<sub>3</sub>, thereby promoting\nthe hydrogenation of reaction intermediates. These findings highlight\nthe crucial role of indium–palladium intermetallic compounds\nin selective CO<sub>2</sub> hydrogenation to methanol.