A Computational Study on Adsorption Configurations and Dissociative Reactions of the HN₃ Molecule on the TiO₂ Anatase (101) Surface

This study investigates the adsorption configurations and the dissociative reactions of HN 3 on the TiO 2 anatase (101) surface by first-principles calculations. The results show that there are six different adsorption configurations of HN 3 adsorbed on the surface. Among those adsorption configurations, the most stable adsorbate configuration is side-on HN(N 2 )−Ti(a), with an adsorption energy of 10.2 kcal/mol. In addition, for the HN 3 fragments, the most stable adsorbate is Ti−(H)N−O(a), with an adsorption energy of 69.8 kcal/mol. The effect of the H present in the coadsorbed configuration significantly increases the adsorption energy by 46.4, 44.2, and 49.2 kcal/mol for the adsorbates of N 3 −Ti(a), Ti−N 3 −O(a), and Ti−N 3 −Ti(a), respectively. The lowest two energy levels for dissociative adsorbates are Ti−(H)N−O(a) + N 2 −Ti(a) and N 3 −Ti(a) a + H−O(a), and their energies are 5.7 and −12.8 kcal/mol, respectively. In addition, for the latter dissociative adsorbates, the two lowest energy barriers for these adsorbates that transit from their initial end-to-end Ti−N 3 H···O*(a) and end-to-end Ti−N 3 H−O(a) are approximately 2.6 kcal/mol. The comparison made between HN 3 on both anatase and rutile surfaces shows that the reactions of dissociative adsorptions of HN 3 are endothermic for Ti−(H)N−O(a) + N 2 −Ti(a) and exothermic for N 3 −Ti(a) a + O−H(a) on the anatase (101) surface, while both are exothermic on the rutile (110) surface.