The synthesis mechanism of nitrogen to ammonia on the Fe, Co, Ni-doped Cu(100) Surface: A DFT study

The density functional theory calculations were carried out to investigate the mechanism of N-2-to-NH3 on the pure Cu(100) and TMn/Cu(100) (TM = Fe, Co, Ni and Cu; n = 1, 4 and 9) bimetallic catalysts.. The results showed that the most stable adsorption configurations of N-2 on the pure Cu(100) and TMn/Cu(100) surfaces were sensitive to the catalyst composition. Especially on the TM4/Cu(100) surface, N-2 with a flat style absorbed on the TM4/Cu(100) surface, which indicated that the hydrogenation of N-2 is more feasible. The mechanism indicated that N-2 the Co-4/Cu(100) surface was reduced to NH3 via an associative mechanism and the activation barrier required by N-2 reduction was the lowest, which was the most favorable for N-2-to-NH3. And the formation of the NNH* intermediate was favorable to overcome the limitation of the BEP relationship. The activation barrier of N* hydrogenation with the co-adsorption NH3* was higher. Finally, the results of microkinetics analysis suggested that, when the pressure ratios of H-2 to N-2 was 1 and the total pressure was 1 bar, the turnover frequency for NH3 reached the maximum value of 1.7%. This may provide the significant guidance for the design multiphase Cu-based bimetallic catalysts for N-2-to-NH3.

Automated summary

The study reveals differences in the adsorption and conversion mechanisms of N-2 on different bimetallic catalyst surfaces, with the Co-4/Cu(100) catalyst showing the most favorable conversion of N-2 to NH3, providing important guidance for the design of Cu-based bimetallic catalysts.