A series of palladium (2 wt.%) catalysts supported on silica (301 m²/g) and loaded with increasing amount of gallium – ratio of Ga/Pd = 2, 4 and 8 atom/atom – were investigated for CO₂ hydrogenation to methanol. The turnover frequency to methanol (H₂/CO₂ = 3; 523 K, 3 MPa), based on surface palladium, showed a 200-fold enhancement as compared to the monometallic Pd/SiO₂ catalyst. Additionally, the apparent activation energy for methanol synthesis decreased from 60 kJ/mol on Pd/SiO₂ to ∼40 kJ/mol on the supported Ga-Pd catalysts. Characterization of the Pd-Ga catalyst series by X-ray absorption spectroscopy and high resolution transmission electron microscopy indicates the formation of Pd₂Ga bimetallic nanoparticles partially covered by a thin layer of Ga₂O₃ on the silica surface. In situ infrared spectroscopy was employed to examine the reaction mechanism during the CO₂ adsorption and hydrogenation at 0.7 MPa. It is proposed a bifunctional pathway where the carbonaceous species bound to the gallium oxide surface are hydrogenated, stepwise, to formate and methoxy groups by atomic hydrogen, which spillovers from the Pd-Ga bimetallic nanoparticles.

研究了一系列负载在二氧化硅 (301 m ² /g)上的钯 (2 wt.%) 催化剂 ( Ga/Pd 的比率 = 2、4 和 8 原子/原子) 用于 CO ₂加氢到甲醇。与单金属 Pd/SiO ₂催化剂相比，基于表面钯的甲醇转化频率（H ₂ /CO ₂ = 3；523 K，3 MPa）显示出 200 倍的增强。此外，甲醇合成的表观活化能从 60 kJ/mol 在 Pd/SiO _{2 上降低}在负载型 Ga-Pd 催化剂上达到 ~40 kJ/mol。通过 X 射线吸收光谱和高分辨率透射电子显微镜对 Pd-Ga 催化剂系列的表征表明，在二氧化硅表面上形成了部分被 Ga ₂ O ₃薄层覆盖的 Pd ₂ Ga 双金属纳米粒子。采用原位红外光谱研究了0.7 MPa下CO ₂吸附和加氢过程中的反应机理。提出了一种双功能途径，其中与氧化镓表面结合的碳质物质逐步氢化以通过原子氢形成甲酸基团和甲氧基，氢原子从 Pd-Ga 双金属纳米粒子溢出。