The PdFe, PdGa, and PdIn intermetallic compounds in CO₂ hydrogenation to methanol: structure and catalytic properties

The PdM intermetallic systems of various compositions (M = Fe, Ga, In) deposited on SiO₂ were used to establish the relationship between the surface structure, phase composition of nanoparticles, and the behavior in the catalytic hydrogenation of carbon dioxide to methanol. The PdFe/SiO₂ catalyst showed a high activity, but a very low methanol selectivity (2.7%). The activity of PdGa/SiO₂ was slightly lower, while the selectivity was much higher (40%). The PdIn/SiO₂ catalyst had the most promising catalytic performance over a wide range of operating temperatures (220–310 °C). Regarding the maximum selectivity (68.4%) and methanol productivity (0.85 g_MeOH g_Pd+In⁻¹ h⁻¹), this catalyst markedly surpassed both the monometallic Pd catalyst and the Cu/ZnO/Al₂O₃ reference sample. The enhanced efficiency can be attributed to two key factors: more homogeneous phase composition of the nanoparticles and a unique structure of the active sites caused by the large electronegativity difference between the Pd and In atoms.