Rational Design of Indium–Palladium Intermetallic Catalysts for Selective CO<sub>2</sub> Hydrogenation to Methanol
Jiabao Lv, Hongman Sun, Guanying Liu, Tong Liu, Guofeng Zhao, Youhe Wang, Xin Tu, Zifeng Yan
Abstract
Indium–palladium intermetallic catalysts have shown great potential for CO 2 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-ZrO 2 demonstrated the highest reactivity (5.1 mmol/g cat /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 In 3 Pd 2 which is close to the In 2 O 3 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 In 3 Pd 2 and In 2 O 3: In 2 O 3 tends to adsorb and activate CO 2, while In 3 Pd 2 has an advantage for the dissociation of H 2, which could compensate for the insufficient ability of In 2 O 3, thereby promoting the hydrogenation of reaction intermediates. These findings highlight the crucial role of indium–palladium intermetallic compounds in selective CO 2 hydrogenation to methanol.