Hydrogen induced metallization of ZnO (11̅00) surface: Ab initio study

Usseinov, А.; Kotomin, E. A.; Аkilbekov, A.; Zhukovskii, Yuri F.; Purans, J.

doi:10.1016/j.tsf.2013.11.021

Cited by 16 publications

(11 citation statements)

References 34 publications

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“…Within the self‐consistency, the accuracies (tolerances) 10 −7 , 10 −8 , 10 −7 , 10 −7 , 10 −14 have been chosen for calculations of Coulomb and exchange integrals . As criteria for verification of simulations, the lattice constants calculated for the wurtzite‐based ZnO bulk ( a 0 = 0.326 nm, c 0 = 0.521 nm, and free parameter for regular O sites u = 0.382) have been found in excellent agreement with those observed experimentally ( a 0 = 0.325 nm, c 0 = 0.520 nm, and u = 0.382) . The band gap calculated for ZnO bulk has been estimated to be 3.52 eV ( cf .…”

Section: Theoretical Backgroundsupporting

confidence: 64%

“…Arbitrary nanowires can be stabilized when they are terminated by lateral facets, which possess the smallest surface energy among any wurtzite faces. This requirement is fulfilled for the family of six identical

{1 \overset{1}{true} 00},

{\overset{1}{true} 100},

{10 \overset{1}{true} 0},

{\overset{1}{true} 010},

{01 \overset{1}{true} 0}

, and

{0 \overset{1}{true} 10}

facets of zinc oxide, since they possess the smallest surface energy among wurtzite faces . The latest version of the CRYSTAL code used for ab initio calculations on ZnO NWs contains the new option NANOROD allowing the users, for the first time, to generate differently structured 1D nanowires when setting the properly chosen Miller indices of their lateral facets and, thus, simultaneously defining their crystallographic orientations .…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Zhukovskii

Piskunov

Lisovski

et al. 2016

Physica Status Solidi (b)

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Zinc oxide (ZnO) is considered in general as a promising material for solar water splitting. Its wurtzite-structured bulk samples, however, can be considered as active for photocatalytic applications only under UV irradiation, where they possess $1% efficiency of sunlight energy conversion due to their wide band gap (3.4 eV). Although pristine ZnO nanowires (NWs) possess noticeably narrower band gaps than the bulk, the tendency of band gap reduction with increasing NW diameter is insufficient, and further modification is required. We have contributed to filling this gap by performing a series of ab initio calculations on ZnO NWs of different diameters (d NW ), which are mono-doped by metal (Ag) and non-metal atoms (C, N) or contain oxygen vacancies with varied concentration ($3 vs. $6%). To reproduce qualitatively the energies of one-electron states of nanowires in our calculations, the hybrid DFT þ HF Hamiltonian has been used, based on the PBE0 exchange-correlation functional. We have analyzed changes in the electronic structure induced in a few defect composition scenarios, showing that, for specific concentrations and locations of the dopants, the optical absorption peak of doped ZnO can be shifted to the visible light range with promising efficiency. In agreement with experimental observation, the most significant results have been achieved for carbon-doped ZnO nanowires. They possess the highest photocatalytic suitability, since the band gap is reduced in this case down to 2.1-2.2 eV (for nanowire diameters of 2.9-3.5 nm), which corresponds to optimal 15-17% efficiency of solar energy conversion.

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Section: Theoretical Backgroundsupporting

confidence: 64%

{1 \overset{1}{true} 00},

{\overset{1}{true} 100},

{10 \overset{1}{true} 0},

{\overset{1}{true} 010},

{01 \overset{1}{true} 0}

, and

{0 \overset{1}{true} 10}

Section: Theoretical Backgroundmentioning

confidence: 99%

Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Zhukovskii

Piskunov

Lisovski

et al. 2016

Physica Status Solidi (b)

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“…A 20-layer ZnO(11̅00) slab model was chosen for simulations of zinc oxide substrate (thickness of which corresponds to [0001]-oriented NW possessing diameter of 3.5 nm) and its coverage by WS 2 nanolayers from both sides. Atomistic models used for simulation of hydrogen molecule reactivity toward ZnO(11̅00) substrate have been constructed by us recently …”

Section: Theoretical Sectionmentioning

confidence: 99%

Unexpected Epitaxial Growth of a Few WS₂ Layers on {11̅00} Facets of ZnO Nanowires

et al. 2016

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Core–shell nanowires are an interesting and perspective class of radially heterostructured nanomaterials where epitaxial growth of the shell can be realized even at noticeable core–shell lattice mismatch. In this study epitaxial hexagonally shaped shell consisting of WS2 nanolayers was grown on {11̅00} facets of prismatic wurtzite-structured [0001]-oriented ZnO nanowires for the first time. A synthesis was performed by annealing in a sulfur atmosphere of ZnO/WO3 core–shell structures, produced by reactive dc magnetron sputtering of an amorphous a-WO3 layer on top of ZnO nanowire array. The morphology and phase composition of synthesized ZnO/WS2 core–shell nanowires were confirmed by scanning and transmission electron microscopy (SEM and TEM), micro-Raman, and photoluminescence spectroscopy. Epitaxial growth of WS2(0001) layer(s) on {11̅00} facets of ZnO nanowire is unexpected due to incompatibility of their symmetry and structure parameters. To relax the interfacial incoherence, we propose a model of ZnO/WS2 interface containing WS2 bridging groups inside and use first-principles simulations to support its feasibility.

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\{1 \overline{1} 00\}, \{\overline{1} 100\}, \{10 \overline{1} 0\}, \{\overline{1} 010\}, \{01 \overline{1} 0\}

and

({}, 0 \overset{1}{true} 10)

facets of zinc oxide, since they possess the smallest surface energy among wurtzite faces . The last edition of CRYSTAL14 code, used for our calculations on ZnO nanowires, contains the new option NANOROD, allowing users to generate differently structured NWs when setting the properly chosen Miller indices of their lateral facets, and thus, simultaneously defining their crystallographic orientations…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…This requirement is fulfilled for the family of six identical 1 " 100 ÈÉ ; " 1100 ÈÉ ; 10 " 10 ÈÉ ; " 1010 ÈÉ ; 01 " 10 ÈÉ and 0 " 110 ÈÉ facets of zinc oxide, since they possess the smallest surface energy among wurtzitef aces. [102] Thel ast edition of CRYSTAL14 code,u sed for our calculations on ZnO nanowires,c ontainst he new option NANOROD,a llowing userst og enerate differently structured NWs when setting the properly chosen Milleri ndices of their lateral facets,a nd thus,s imultaneously defining theirc rystallographico rientations. [92] To estimate the suitability of doped [0001]-oriented ZnO NWs of different sizes for photocatalytic applications,w eh ave preliminarily considered pristine NWs of three different diameters (Table 4), whichc an be cut from ah ost wurtzite-type crystal.…”

Section: Atomistic Models Of Doped Zno Nanowiresmentioning

confidence: 99%

Doped 1D Nanostructures of Transition‐metal Oxides: First‐principles Evaluation of Photocatalytic Suitability

Zhukovskii

Piskunov

Lisovski

et al. 2016

Israel Journal of Chemistry

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The splitting of water molecules under the influence of solar light on semiconducting electrodes is a clean and renewable source for the production of hydrogen fuel. Its efficiency depends on the relative position of the band‐gap edges or the induced defect levels with a proper band alignment relative to the redox H+/H2 and O2/H2O potentials. For example, TiO2 and ZnO bulk, as well as thick slabs (whose band gaps are ∼3.2–3.4 eV), can be active only for photocatalytic applications under UV irradiation (possessing ∼1 % solar energy conversion efficiency). Nevertheless, by adjusting the band gap through formation of nanostructures and further doping, the efficiency can be increased up to ∼15 % (for 2.0–2.2 eV band gap). We analyse results of DFT (density functional theory) calculations on TiO2 nanotubes and ZnO nanowires, both pristine and doped (e.g., by AgZn, CO, FeTi, NO and SO substitutes). To reproduce the energies of one‐electron states better, we have incorporated the Hartree‐Fock (HF) exchange into the hybrid DFT+HF Hamiltonian. Both the atomic and electronic structure of nanomaterials, simulated by us, are analysed to evaluate their photocatalytic suitability, including positions of the redox potential levels inside the modified band gap, the width of which corresponds to visible‐light energies. Analysis of the densities of states (DOS) for considered nanostructures clearly shows that photocatalytic properties can be significantly altered by dopants. The chosen hybrid methods of first‐principles calculations significantly simplify selection of suitable nanomaterials possessing the required photocatalytic properties under solar light irradiation.

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Hydrogen induced metallization of ZnO (11̅00) surface: Ab initio study

Cited by 16 publications

References 34 publications

Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Unexpected Epitaxial Growth of a Few WS₂ Layers on {11̅00} Facets of ZnO Nanowires

Doped 1D Nanostructures of Transition‐metal Oxides: First‐principles Evaluation of Photocatalytic Suitability

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Hydrogen induced metallization of ZnO (11̅00) surface: Ab initio study

Cited by 16 publications

References 34 publications

Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation

Unexpected Epitaxial Growth of a Few WS2 Layers on {11̅00} Facets of ZnO Nanowires

Doped 1D Nanostructures of Transition‐metal Oxides: First‐principles Evaluation of Photocatalytic Suitability

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Unexpected Epitaxial Growth of a Few WS₂ Layers on {11̅00} Facets of ZnO Nanowires