Comparative hydrogen adsorption on the pure Al and mixed Al-Si nano clusters: A first principle DFT study

- Hydrogen adsorption is exothermic and chemisorption type.
- Si atom is more suitable for hydrogen adsorption than Al atom.
- Structural destabilization of the clusters occur as a result of hydrogen adsorption.
- AlnSimH2 clusters are more stable than corresponding AlnH2 clusters.

Hydrogen adsorption on the pure Aln and mixed AlnSim (n = 5-7, n + m = 5-7) nano clusters were investigated using B3LYP hybrid density functional method. The large negative values of adsorption energy show that adsorption is exothermic and chemisorption type. Adsorption energies vary not only with cluster size but also with cluster composition. Adsorption of hydrogen on the Si atom is energetically more favorable than adsorption on the Al atom in almost all of clusters. The positive values of distortion energy for all clusters indicate structural destabilization of the clusters as a result of hydrogen adsorption. The stability and reactivity of hydrogenated clusters were also discussed using binding energy per atom and chemical hardness. Our results reveal that all AlnSimH2 clusters are more stable than corresponding AlnH2 clusters and stability of AlnSimH2 clusters increases with atomic percentage of Si.