Applying computational Materials Design (CMD) toward efficient hydrogen production from water

Hydrogen is probably the most promising solution to our global energy problems for the future. However, in order to support the developing hydrogen economy, efficient processes for hydrogen production and storage become necessary. Now a days, the hydrogen production is a large and growing industry. Globally, some 50 million metric tons of hydrogen are produced in a year. The growth rate is around 10% per year. Hydrogen can be produced using fossil fuels via steam reforming or partial oxidation of natural gas and by coal gasification. Produced in this fashion, hydrogen will generate less CO2 than conventional internal combustion engines (including the emissions during fuel production, delivery, and use in the vehicle), and thus contributes less to global warming. It can also be produced via electrolysis using electricity and water, consuming approximately 50 kilowatt hours of electricity per kilogram. This method is still expensive. The direct thermal splitting of water, 2H2

GW quasiparticle energy study of ternary tetradymite Bi2Te2Se and Bi2Te2S thin films

In this work, we have evaluated the quasiparticle energies of ternary tetradymite Bi2Te2Se and Bi2Te2S using first-principles calculation within the G 0 W 0 methods. We have also performed a broad convergence tests in order to investigate the quasiparticle corrections to the structural parameters and to the semi core d electrons in both of the compounds. For each case, we have calculated the many-body corrections within a one-shot GW method of the compounds. Our results have shown that for Bi2Te2Se the GW corrections increase the band gap to almost 10%, and for specific atomic positions, the band structure shows a close value to the experimental one. For Bi2Te2S, despite increase in the band gap due to the GW corrections, possibility of bulk resistivity that can be significant for photovoltaic applications was observed

Theoretical study for magnetic effect in dissociative adsorption of oxygen to a platinum monolayer on Ni(110) surface

We investigate oxygen dissociative adsorption to a platinum monolayer on Ni(110) surface (Pt/Ni(110))by density functional theory. We have shown that the activation barrier on Pt/Ni(110) is lower than that on a clean Pt(001) surface. This may be due to the effect of magnetization of Pt surface. The reason of decrease of activation barrier can be attributed to the flow of electrons from oxygen to platinum surface because the d orbitals have spin polarization at the Fermi level where the down spin d orbitals are unoccupied

Effect of gallium and arsenide adsorbed on graphene : a first-principles study on structural and electronic properties

In this study, the adsorption influence of two different metals, gallium (Ga) and arsenide (As) adatoms on the stabilities and electronic structure of single graphene layer has been systematically studied using first-principles pseudopotentials calculations within the framework of density functional theory (DFT). The generalized gradient approximation used is PW91 exchange-correlation functional. The results of our calculations reveal that the adsorption of Ga atom on graphene resulted in electron transfer mainly from p-orbital of the Ga adatom to graphene and subsequently, altered the electronic state of graphene by shifting the Fermi level away from Dirac point, up to ∼1.5 eV. Meanwhile, the d-orbitals of Ga adatom have spin polarization at the Fermi level where the minority spin d-orbitals are unoccupied. The As adatom was found to have larger adsorption energy value on H, B and T sites of graphene compared to Ga adatom. Thus, we described this energy difference as a result of the bonding configurations between both Ga and As atoms with carbon in the graphene structure. While B-site favored the adsorption of arsenic adatom, we found that the most favored adsorption site for Ga adatom on graphene is above H-sites

Density functional study of manganese atom adsorption on hydrogen-terminated armchair boron nitride nanoribbons

In this paper, we have investigated stable structural, electric and magnetic properties of manganese (Mn) atom adsorption on armchair hydrogen edge-terminated boron nitride nanoribbon (A-BNNRs) using first principles method based on density-functional theory with the generalized gradient approximation. Calculation shows that Mn atom situated on the ribbons of A-BNNRs is the most stable configuration, where the bonding is more pronounced. The projected density of states (PDOS) of the favored configuration has also been computed. It has been found that the covalent bonding of boron (B), nitrogen (N) and Mn is mainly contributed by s, d like-orbitals of Mn and partially occupied by the 2p like-orbital of N. The difference in energy between the inner and the edge adsorption sites of A-BNNRs shows that Mn atoms prefer to concentrate at the edge sites. The electronic structures of the various configurations are wide, narrow-gap semiconducting and half-metallic, and the magnetic moment of Mn atoms are well preserved in all considered configurations. This has shown that the boron nitride (BN) sheet covered with Mn atoms demonstrates additional information on its usefulness in future spintronics, molecular magnet and nanoelectronics devices

Low coverage palladium adsorption on graphene: first principles study

In this paper, we investigate stable geometries, electronic and magnetic properties of low coverage palladium (Pd) atom adsorption on graphene using first principles calculations with the generalized gradient approximation. Calculations show that single Pd atom located at the top of carbon atom is the energetically favorable configuration, and is found to be semiconductor and non-magnetic. We also compute the projected density of states (PDOS) around Fermi level and beyond. It is found that, C-Pd covalent interaction is mainly dominated by 2 pz of C, 5s and 4d like states of Pd. For low coverage stable Pd dimer, the adsorption is characterized by strong hybridization between the palladium atoms and the two carbon atoms bonded directly to it. A much weakening of Pd–Pd bond is observed and the C-Pd covalent bonds mainly dominate by 2pz of C orbital indicating that planar coating can be achieved. Thus, this work reveals that uniform coating of Pd atom can be achieved and may be useful in transport measurements

Density functional study of spin polarization on a carbon material with a hexagonal structure induced by iron atoms

We investigate the spin polarization of a non magnetic material, e.g., a carbon material made from ten C atoms forming a hexagonal structure with total spin S = 0, induced by a ferromagnetic material, e.g., two Fe atoms with a total spin S = 4. Based on the density functional theory, we calculate the total spin density of the system. Our preliminary results show that the total spin for the ten C atoms changes from S = 0 to S = 4, while the total spin of the two Fe atoms changes from S = 4 to S =0. These results seem to indicate that there is a promising possibility to induce spin polarization on a carbon material by Fe atoms