单原子Ge助剂修饰Cu(111)晶面上CO2加氢制甲醇的机理研究

针对CO₂热催化转化制甲醇过程中CO₂吸附、活化较困难及副产物较多的问题,提出采用单原子Ge助剂修饰Cu(111)晶面的解决思路,通过密度泛函理论(DFT)计算研究了CO₂在Ge-Cu(111)晶面上加氢合成甲醇的反应机理。结果表明,单原子Ge助剂的电子调控增加了与其相邻的 Cu 原子的电子云密度,使 CO₂分子在含 Ge 活性界面上的吸附能力显著增强:CO₂在 Ge-Cu(111)晶面上的吸附能约为Cu(111)晶面的1.5倍,约为Pd改性Cu(111)晶面的2.4倍,进而使逆水煤气变换(RWGS)反应路径速控步骤的活化能降低了近 20 kJ·mol^-1,同时衍生出 3条生成甲醇的 RWGS新路径;此外,Ge-Cu(111)晶面上甲酸盐路径由于速控步骤活化能大幅上升而被禁阻,进而CO及烃类等副产物选择性大幅降低,Ge-Cu(111)晶面上CO₂加氢制甲醇选择性升高。

Theoretical investigation on the mechanism of CO2 hydrogenation to methanol over single atom Ge promoter doped Cu(111) surface

In this work, we proposed a novel strategy, doping single atom Ge promoter to the Cu(111) surface, to overcome the shortcomings such as the difficulties in the adsorption and activation of CO₂ molecules and the complex by-products produced in both the reverse water gas shift (RWGS) and the formate reaction pathway. The electron modulating effect of single atom Ge species on the reaction mechanism of CO₂ hydrogenation to methanol over Ge-Cu(111) surface was detailly investigated by the density functional theory (DFT) method. The results show that the electron supply ability of Cu atoms adjacent to the single Ge atom is greatly enhanced due to the electron modulating effect of Ge species, which leads to the improved interaction between the CO₂ molecule and the active interface:the adsorption energy of CO₂ over the single atom Ge promoted Cu(111) surface was approximately 1.5 times that over the pure Cu(111) surface and approximately 2.4 times that over clustered Pd modified Cu(111) surface, respectively. The enhanced CO₂ adsorption ability further resulted in a decline in the activation energy of the reaction rate control step for the RWGS pathway by about 20 kJ·mol^-1, meanwhile, there emerged three new potential RWGS reaction routes that only produced methanol. Moreover, the formate reaction pathway is kinetically inhibited over the Ge-Cu(111) surface, leading to the reduced by-products such as CO and hydrocarbons to improve both the selectivity of methanol in the CO₂ hydrogenation to methanol reaction.