Breaking the Linear Relation in the Dissociation of Nitrogen on Iron Surfaces

作者：Liu, Dexin; Zhao, Wei; Yuan, Qinghong^*

来源：Chemphyschem : a European journal of chemical physics and physical chemistry , 2022, 23(17): e202200147.

DOI：10.1002/cphc.202200147

• N-2 dissociation
• transition metals
• density of states
• DFT
• iron

Current industrial ammonia synthesis depends on the Haber-Bosch process, in which the activity of the catalyst is limited by the Bronsted-Evans-Polanyi (BEP) principle and Fe is used as a commercial catalyst. Herein, we found that the dissociation barriers of N-2 on Fe(111), Fe(211), Fe(110), and Fe(100) surfaces do not follow the widely accepted BEP principle. N-2 dissociation on Fe(111) surface has the smallest adsorption energy and the lowest energetic barrier. Such an abnormal phenomenon can be attributed to charge transfer from Fe surfaces to the anti-bonding orbital (pi*) of the absorbed N-2. More charges transferred from the Fe surface to pi* of N-2 leads to a weaker N equivalent to N triple bond and a lower adsorption energy of N atoms. However, the hydrogenation of N atoms and desorption of NH3 on the four Fe surfaces follow the BEP principle. Therefore, Fe(111) is found to be the most active surface to promote ammonia synthesis, and such a conclusion is also applicable to Ni and Mo surfaces.