Insights of hydrogen adsorption and dissociation on Ni doped Mg4 clusters: A DFT study

Hydrogen adsorption and dissociation on Mg4 and NiMg3 clusters are studied using DFT method. Physisorption of hydrogen molecule on Mg4 is extremely weak, which however significantly strengthens on Ni doped Mg4 cluster. Following the physisorption mechanism, NiMg3 cluster can adsorb three H2 molecules at most and the cluster geometry plays an important role here. On the other hand, physisorption followed by chemisorption facilitates the growth of hydrogen adsorption process in both Mg4 and NiMg3 clusters. Further, dissociation and diffusion of H2 become more favourable on Ni doped Mg4 cluster resulting in a larger number of H2 adsorbed on NiMg3 compared to that on Mg4. NiMg3 is found to exhibit practically attainable H2 desorption energies lower than those for bare Mg4 clusters.