The synthesis mechanism of nitrogen to ammonia on the Fe, Co, Ni-doped Cu(1 0 0) Surface: A DFT study

The density functional theory calculations were carried out to investigate the mechanism of N2-to-NH3 on the pure Cu(1 0 0) and TMn/Cu(1 0 0) (TM = Fe, Co, Ni and Cu; n = 1, 4 and 9) bimetallic catalysts.. The results showed that the most stable adsorption configurations of N2 on the pure Cu(1 0 0) and TMn/Cu(1 0 0) surfaces were sensitive to the catalyst composition. Especially on the TM4/Cu(1 0 0) surface, N2 with a flat style absorbed on the TM4/Cu(1 0 0) surface, which indicated that the hydrogenation of N2 is more feasible. The mechanism indicated that N2 the Co4/Cu(1 0 0) surface was reduced to NH3 via an associative mechanism and the activation barrier required by N2 reduction was the lowest, which was the most favorable for N2-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 H2 to N2 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 N2-to-NH3.