镍掺杂对Fe催化剂上CO₂加氢制烃影响的理论计算研究

Density functional theory (DFT) calculations were performed to investigate the effect of Ni doping on C₁ and C₂ hydrocarbons production from CO₂ hydrogenation on the Fe catalyst. The CH^* species was found to be the most favorable monomeric CH_x^* species leading to both CH₄ and C₂H₄ formation on Fe(110) and Ni-Fe(110) surfaces. The plausible pathway went through CO₂→ HCOO^*→HCO^*→CH^*. Although CO^* formation from direct dissociation of CO₂ was kinetically more favorable than CO₂ hydrogenation to HCOO^* and COOH^* intermediates on the two surfaces, the subsequent hydrogenation of CO^* to HCO^* was energetically detrimental, resulting in the reverse conversion of HCO^* to CO^* preferred. Further conversion of CH^* species led to either CH₄ via several hydrogenation steps or C₂H₄ through C-C coupling followed by two hydrogenation steps. On monometallic Fe(110), the barrier difference associated with the selectivity determining step was only 0.10 eV, suggesting similar selectivity to CH₄ and C₂H₄. In contrast, when a Ni atom was doped onto Fe(110), the selectivity difference became more pronounced, leading to an enhanced C₂H₄ production on Ni-Fe(110). These results revealed that adding a small amount of Ni could promote CH^* formation from CO₂ hydrogenation, C-C coupling of two CH^* species and the further hydrogenation of C₂ intermediates to ethylene.