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Earth-abundant quaternary chalcogenides are promising candidate materials for thin-film solar cells. Here we have synthesized Cu2NiSnS4 nanocrystals and thin films in a novel zincblende type cubic phase using a facile hot-injection method. The structural, electronic, and optical properties are studied using various experimental techniques, and the results are further corroborated within first-principles density functional theory based calculations. The estimated direct band gap ~ 1.57 eV and high optical absorption coefficient ~ 106 cm-1 indicate potential application in a low-cost thin-film solar cell. Further, the alignments for both conduction and valence bands are directly measured through cyclic voltametry. The 1.47 eV electrochemical gap and very small conduction band offset of -0.12 eV measured at the CNTS/CdS heterojunction are encouraging factors for the device. These results enable us to model carrier transport across the heterostructure interface. Finally, we have fabricated a CNTS solar cell device for the first time, with high open circuit voltage and fill factor. The results presented here should attract further studies. [ABSTRACT FROM AUTHOR]

The dynamical properties of physically and chemically adsorbed water molecules at pristine hematite-(001) surfaces have been studied by means of equilibrium Born–Oppenheimer molecular dynamics (BOMD) in the NVT ensemble at 298 K. The dissociation of water molecules to form chemically adsorbed species was scrutinised, in addition to ‘hopping’ or swapping events of protons between water molecules. Particular foci have been dynamical properties of the adsorbed water molecules and OH− and H3O+ ions, the hydrogen bonds between protons in water molecules and the bridging oxygen atoms at the hematite surface, as well as the interactions between oxygen atoms in adsorbed water molecules and iron atoms at the hematite surface. Experimental results for photoelectrical current generation complement simulation findings of water dissociation. [ABSTRACT FROM AUTHOR]

Abstract: The hydrogen storage capacity of Ti-acetylene (C2H2Ti) and Li-acetylene (C2H2Li) complex has been tested using second order Møller Plesset method with different basis sets. Single Ti(Li) decorated acetylene complex can adsorb maximum of five(four) hydrogen molecules, which corresponds to the gravimetric hydrogen storage capacity of 12(19.65) wt % and it meets the target of 9 wt % by 2015 specified by US Department of Energy. The hydrogen adsorption energies with zero point energy and Gibbs free energy correction show that hydrogen adsorption on C2H2Ti is energetically favourable for a wide range of temperature and that is unfavourable on C2H2Li complex even at a very low temperature. Atom centered density matrix propagation molecular dynamics simulations reveal that four H2 molecules remain adsorbed on C2H2Ti complex at 300 K. Though H2 uptake capacity of C2H2Li complex is higher than that of C2H2Ti complex, the thermochemistry results favour to C2H2Ti complex over C2H2Li complex as a possible hydrogen storage media. [Copyright &y& Elsevier]

Density functional theory (DFT) and Fourth-order Möller-Plesset (MP4) perturbation theory calculations are performed to examine the possibility of hydrogen storage in V-capped VC3H3 complex. Stability of bare and H2 molecules adsorbed V-capped VC3H3 complex is verified using DFT and MP4 method. Thermo-chemistry calculations are carried out to estimate the Gibbs free corrected averaged H2 adsorption energy which reveals whether H2 adsorption on V-capped VC3H3 complex is energetically favorable, at different temperatures. We use different exchange and correlation functionals employed in DFT to see their effect on H2 adsorption energy. Molecular dynamic (MD) simulations are performed to confirm whether this complex adsorbs H2 molecules at a finite temperature. We elucidate the correlation between H2 adsorption energy obtained from density functional calculations and retaining number of H2 molecules on VC3H3 complex during MDs simulations at various temperatures. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]

Abstract: Calculations of the ability of titanium–ethylene complexes of the type, Ti:C2H4, to absorb molecular hydrogen have been performed using density functional theory. A maximum of 5H2 molecules can be adsorbed on Ti:C2H4 thereby giving an uptake capacity of 11.72 wt%, in excellent agreement with previous experimental results reported by two of us (Phys. Rev. Lett., 100, 105505, 2008). Calculations of the vibrational frequencies in such complexes with both H2 and D2, Ti:C2H4(nH2) and Ti:C2H4(nD2), n = 1–5, have also been performed and the values obtained used to find the Equilibrium Isotope Effect (EIE). Measurements of the EIE are also reported and these are in excellent agreement with the EIE calculated for 5H2 molecules adsorbed in the complex. [Copyright &y& Elsevier]

Abstract: This work reports the hydrogen uptake capacity of V-capped and V-inserted VC3H3 organometallic complexes using density functional theory (DFT) with different exchange and correlation functionals. Maximum of five and three H2 molecules are adsorbed on V-capped and V-inserted VC3H3 structures, respectively. This corresponds to the hydrogen uptake capacity of 10.07 and 6.66 wt% for the former and the latter, respectively. The first added hydrogen molecule is adsorbed in dihydride form on V-capped as well as V-inserted VC3H3 complex. A complex with a dissociated hydrogen molecule adsorbed has higher binding energy than that of molecular hydrogen adsorbed. The nature of interactions between H2 molecules and organometallic complex is studied using many-body analysis approach. Thermo-chemistry calculations are performed to see whether H2 adsorption on V-capped complex is energetically favorable or not for room temperature hydrogen storage. [Copyright &y& Elsevier]

We have studied H2 adsorption on C3H3V organometallic compound using density functional method at B3LYP/LanL2Dz level of theory. It was found that H2 molecule dissociates and adsorbed in dihydride form on this organometallic compound. Potential energy surface for H2 dissociation process was obtained and different properties such as HOMO–LUMO gap, dipole moment, interaction energies between different molecules and atoms, vibrational frequencies, and atomic charges during the dissociation process were studied. It was found that the C3H3V(H2) structure is most stable at H&bond;V&bond;H angle of 66.3°. Many-body analysis was also carried out to determine the two-body energies, three-body energies, relaxation energy, and binding energy of the structures for each point on the potential surface. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

We report the gravimetric hydrogen uptake capacity of C2H4Sc complex and isoelectronic ions using Density Functional Theory. We predict that C2H4Sc+ can bind maximum seven hydrogen molecules in dihydrogen form giving gravimetric uptake capacity of 16.2 wt %, larger by about 2 and 4 wt % than the neutral and anion, respectively. We also found that the interaction of hydrogen molecules with C2H4Sc+ ion is characteristically different than that with neutral and anion. Vibrational spectroscopic study reveals that C2H4Sc and isoelectronic ions are quantum mechanically stable with their characteristic change in respective identified mode. The large gravimetric H2 uptake capacity of C2H4Sc+ is well above the target specified by Department of Energy (DOE) by 2015. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [ABSTRACT FROM AUTHOR]

Organic semiconductors have recently emerged as promising catalytic materials for oxygen reduction to hydrogen peroxide, H 2 O 2 , a chemical of great importance in industry as well as biology. While examples of organic semiconductor-mediated photocatalytic and electrocatalytic processes for H 2 O 2 production become more numerous and improve in performance, fundamental understanding of the reaction mechanisms at play have been explored far less. The aim of the present work is to computationally test hypotheses of how selective oxygen reduction to H 2 O 2 generally occurs on carbonyl dyes and pigments. As an example material, we consider epindolidione (EPI), an industrial pigment with demonstrated semiconductor properties, which photocatalytic activity in oxygen reduction reaction (ORR) and thereby producing hydrogen peroxide (H 2 O 2 ) in low pH environment has been recently experimentally demonstrated. In this work, the ability of the reduced form of EPI, viz. EPI-2H (which was formed after a photoinduced 2e - /2H + process), to reduce molecular triplet oxygen to peroxide and the possible mechanism of this reaction are computationally investigated using density functional theory. In the main reaction pathway, the reduction of O 2 to H 2 O 2 reaction occurs via abstraction of one of the hydrogen atoms of EPI-2H by triplet dioxygen to produce an intermediate complex consisting of the radicals of hydrogen peroxide (HOO • ) and EPI-H • at the initial stage. HOO • thus released can abstract another hydrogen atom from EPI-H • to produce H 2 O 2 and regenerates EPI; otherwise, it can enter another pathway to abstract hydrogen from a neighboring EPI-2H to form EPI-H • and H 2 O 2 . EPI, after reduction, thus plays in ORR the role of hydrogen atom transfer (HAT) agent via its OH group, similar to anthraquinone in the industrial process, while HAT from its amino hydrogen is found unfavorable.