Seemita Banerjee

First-principles study of the H2 interaction with transition metal (Ti, V, Ni) doped Mg(0001) surface: Implications for H-storage materials

Using first-principles calculations we have investigated the interaction of hydrogen molecules with clean and M (Ti, V, and Ni) doped Mg(0001) surfaces. The calculations have been carried out using plane-wave-based pseudopotential method under the formalism of density functional theory. First we have calculated the stability of the M atoms on the Mg surface. On the basis of the energetic criteria, we found that all these M atoms prefer to substitute one of the Mg atoms from the second layer than the top surface atom. In the second step we have studied the interaction of a hydrogen molecule with the clean and doped Mg surface. The results show that for M atoms at the surface, the hydrogen molecule undergoes spontaneous dissociative chemisorptions. However, for M atoms in the second layer, it requires to cross an activation barrier to undergo molecular dissociation. Furthermore, to understand the mobility of hydrogen atoms on the surface we have calculated the diffusion energy barriers for the M doped surface. Contrary to the molecular dissociation behavior, it is found that the mobility of hydrogen atoms on the surface is easier if the M atoms are placed in the second layer in comparison to that in the top surface layer. It is believed that the results of the present study provide useful information based on the first-principles calculations for synthesizing Mg based materials for hydrogen storage with optimal performance.

Nature of the Pd–CNT interaction in Pd nanoparticles dispersed on multi-walled carbon nanotubes and its implications in hydrogen storage properties

Oleyl amine stabilised Pd nanoparticles have been prepared by reverse micro-emulsion method and supported on multi walled CNTs. TEM studies have confirmed that Pd nanoparticles, having sizes in the range of 3–5 nm, are well dispersed on the CNTs. Based on 13C MAS NMR and TG-DTA studies it is inferred that the Pd nanoparticles interact with CNT support to form sp3 carbon species, which get effectively dispersed on the CNTs. Such finely dispersed Pd nanoparticles facilitate the spillover of hydrogen to the CNT support and improve the hydrogen storage capacity.

Conformers of hydrogenated SiC honeycomb structure: A first principles study

The structural and electronic properties of fully hydrogenated SiC graphane-like nano-structures have been investigated. The objective of this study is to underscore the relative stability of different conformers of hydrogenated SiC sheet. All calculations are carried out using plane wave based pseudo-potential approach under the density functional theory. The results reveal that the fully hydrogenated SiC sheet forms five stable isomers, and the chair conformer is most stable. Further study through molecular dynamic simulation strategy demonstrates that even at room temperature the chair conformer remains stable.

Synthesis, characterization and hydrogen storage studies on porous carbon

Porous carbon sample has been prepared, using zeolite-Y as template followed by annealing at 800°C, with view to estimate the extent of hydrogen storage by the sample. Based on XRD, 13C MAS NMR and Raman spectroscopic studies it is confirmed that the porous Carbon sample contains only sp2 hybridized carbon. The hydrogen sorption isotherms have been recorded for the sample at 273, 223K and 123K and the maximum hydrogen absorption capacity is found to be 1.47wt% at 123K. The interaction energy of hydrogen with the carbon framework was determined to be ∼ 10 kJ mol−1at lower hydrogen uptake and gradually decreases with increase in hydrogen loading.

Pd doped reduced graphene oxide for hydrogen storage

Pd nanoparticles dispersed reduced graphene oxide sample has been prepared by a simple chemical method using hydrazine as the reducing agent. Based on XRD and 13C MAS NMR studies it is confirmed that, Pd nanoparticles are effectively mixed with the reduced graphene oxide sample. Maximum hydrogen storage capacity has been estimated to be ∼1.36 wt % at 123K. Improved hydrogen storage capacity of Pd incorporated sample can be explained based on the phenomenon of spillover of atomic hydrogen.

Structural and Mössbauer spectroscopic study of cubic phase hydrogen storage alloys Ti2Nb1−xFex

The cubic phase alloys Ti2Nb1−xFex (x = 0.0, 0.4, 0.6) have been prepared by an arc melting method. The crystal structure and hyperfine interactions have been carried out using X-ray diffraction and Mossbauer spectroscopy, respectively. Room temperature 57Fe Mossbauer spectra could be fitted with one doublet and four doublets for the alloys and their hydrides, respectively. The hydrogen absorption capacity increases with increase in Fe substitution.