N₂ reduction to NH₃ on surfaces of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ catalysts

The abilities of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ as catalysts for N₂-RR to create the NH₃ are investigated by theoretical levels. The ∆E_adoption and ∆E_formation of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ are investigated. The ∆E_adsorption of N₂-RR intermediates and ΔG_reaction of reaction steps of N₂-RR on Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ are examined. In acceptable mechanisms, the *NN → *NNH step is potential limiting step and *NN → *NNH step in enzymatic mechanism is endothermic reaction. The ∆G_reaction of *NHNH2 → *NH₂NH₂ step on Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ are -0.904, -0.928, -0.860, -0.882, -0.817 and -0.838 eV, respectively. The Co-Al₁₈P₁₈ and Ni-Al₂₁N₂₁ have the highest ∆G_reaction values for reaction steps of N₂-RR. Finally, it can be concluded that the Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄ and Mn-B₂₇P₂ have acceptable potential for N₂-RR by acceptable pathways.

The structures of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ and N₂-RR intermediates are optimized by PW91PW91/6-311+G (2d, 2p) and M06-2X/cc-pVQZ as theoretical levels in GAMESS software. The convergence for force set displacement of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ and N₂-RR intermediates are 1.5 × 10⁵ Hartree/Bohr and 6.0 × 10^-5 Angstrom. The Opt = Tight and MaxStep = 30 are considered to optimize Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ and N₂-RR intermediates. The frequencies of Co-Al₁₈P₁₈, Ni-Al₂₁N₂₁, Fe-B₂₄N₂₄, Mn-B₂₇P₂₇, Ti-C₆₀ and Cu-Si₇₂ and N₂-RR intermediates are calculated.