Elucidating the dissociative and associative mechanisms on the surface-anchored Fe3 cluster under the effect of external electric field

Abstract

In the Haber-Bosch process, the direct dissociation of the N-N bond requires harsh reaction conditions. Three-atom metal clusters exhibit excellent catalytic performance in ammonia synthesis under mild conditions. They are considered potential catalysts to promote the associative hydrogenation of NN*. Moreover, it has been reported that electric fields can be a powerful tool for enhancing the performance of heterogeneously catalyzed reactions. Whether electric fields can further promote ammonia synthesis on three-atom metal clusters and its regulation mechanism needs to be investigated. In this work, we illustrate the effects of the electric fields on the N2 adsorption process, the NN* associative hydrogenation process, the N-N bond direct dissociation process, and the NNH* dissociation process for Fe3 cluster. The results show that the positive external electric field promotes the N2 adsorption process and activates the N-N bond of the NN* and NNH* species. With the increase of electric fields, the initial and final states of the N2 adsorption and NNH* dissociation processes become more stable. In addition, the electric field impedes electron transfer during the N2 adsorption process and the NN* associative hydrogenation process. This research will guide future work on applying electric fields to ammonia synthesis catalyzed by three-atom metal clusters.