Adsorption and Dehydrogenation Behaviors of the NH3 Molecule on the W(111) Surface: A First-Principles Study

The adsorption and dehydrogenation behaviors of ammonia on W(111) surface have been studied by employing spin-polarized density function theory calculations. In this work, three adsorption sites of the W(111) surface were considered, such as top (T), 3-fold-shallow (S), and 3-fold-deep (D) sites. The most stable structures of each NHx (x = 0-3) species on the W(111) surface have been predicted, and the corresponding dehydrogenation processes were found to be via two specific paths (A and B). In PATH A, the calculated activation energies for NHx (x = 1-3) dehydrogenations are 27.66 kcal/mol (for H2N-H bond activation), 32.66 kcal/mol (for HN-H bond activation) and 27.84 kcal/mol (for N-H bond activation), respectively, and the entire process is exothermic by 41.63 kcal/mol. On the other hand, in PATH B, the corresponding activation barriers are 35.97, 29.99, and 29.80 kcal/mol, respectively, and the entire process is 42.19 kcal/mol exothermic. To gain more insight into catalytic processes of the aforementioned conducts, the interaction nature between the adsorbate and substrate is analyzed via detailed electronic analysis.