Photocatalysis Using GaN Nanowires

Jung, Hye Seong; Hong, Young June; Li, Yirui; Cho, Jeonghui; Kim, Yong-Jin; Yi, Gyu‐Chul

doi:10.1021/nn700320y

Cited by 191 publications

(127 citation statements)

References 12 publications

(29 reference statements)

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“…[6][7] For example, GaN is one of the nitride semiconductors that have been studied for photocatalytic applications [8][9][10][11] because its CBM and VBM straddle the hydrogen reduction (H + /H 2 ) and water oxidation (H 2 O/O 2 ) potentials. Although GaN has a large bandgap (3.4 eV), indium alloying to form InGaN can tune the bandgap from the ultraviolet to the near infrared region 12 encompassing the entire solar spectrum.…”

Section: Introductionmentioning

confidence: 99%

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

et al. 2012

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Three dimensional hierarchical nanostructures were synthesized by the halide chemical vapor deposition (HCVD) of InGaN nanowires on Si wire arrays. Single phase InGaN nanowires grew vertically on the sidewalls of Si wires and acted as a high surface area photoanode for solar water splitting. Electrochemical measurements showed that the photocurrent density with hierarchical Si/InGaN nanowire arrays increased by 5 times compared to the photocurrent density with InGaN nanowire arrays grown on planar Si (1.23 V vs RHE). High resolution transmission electron microscopy showed that InGaN nanowires are stable after 15 hours of illumination. These measurements show that Si/InGaN hierarchical nanostructures are a viable high surface area geometry for stable solar water splitting. KEYWORDS:Hierarchical nanostructure, InGaN nanowire, Si wire, photoanode, solar water splitting IntroductionPhotolysis of water with semiconductor materials has been investigated as a clean and renewable energy conversion process by storing solar energy in chemical bonds such as hydrogen. [1][2][3] Since Fujishima and Honda 4 reported the capability of water splitting with TiO 2 , metal oxide semiconductors have been studied extensively due to their stability under photo-anodic conditions. [5][6] However, the valence band of metal oxide semiconductors consists mainly of O 2p orbitals resulting in a low energy maximum (around +3 V vs NHE compared to +1.23 V vs NHE for the water oxidation reaction). This leads to a significant loss in energy from the large difference in potential between the valence band and water oxidation reaction. In addition, lowering the metal oxide bandgap energy for visible light absorption generally comes at the cost of moving the conduction band minimum (CBM) towards lower potentials than the hydrogen reduction potential which cannot perform spontaneous solar water splitting.On the other hand, metal nitrides have less positive valence band maximum (VBM) potentials than metal oxides because N 2p orbitals have smaller ionization energies than O 2p orbitals. [6][7] For example, GaN is one of the nitride semiconductors that have been studied for photocatalytic applications [8][9][10][11] because its CBM and VBM straddle the hydrogen reduction (H + /H 2 ) and water oxidation (H 2 O/O 2 ) potentials. Although GaN has a large bandgap (3.4 eV), indium alloying to form InGaN can tune the bandgap from the ultraviolet to the near infrared region 12 encompassing the entire solar spectrum. The In 0.5 Ga 0.5 N alloy has a bandgap of around 2.0 eV which is desirable for overall water splitting considering the overpotential for the water oxidation reaction. [13][14] Moses et al. 15 calculated that the VBM of InGaN alloy increases in energy almost linearly with indium composition. Therefore, the InGaN alloy was suggested to accomplish spontaneous overall water splitting with up to 50% indium incorporation since both the CBM and VBM can satisfy the energetic requirements. Experimentally, single crystalline In x Ga 1-x N nanowire...

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Section: Introductionmentioning

confidence: 99%

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

et al. 2012

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“…27 Additionally, one dimensional nanowire structures are expected to have significantly improved photocatalytic activity due to their high surface-to-volume ratio and much more efficient charge carrier separation. [29][30][31][32] These attributes, therefore, make III-nitride nanowire structures a very promising, yet less explored candidate as a photocatalyst material.…”

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Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

Chowdhury

Kibria

et al. 2015

APL Materials

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The performance of photochemical water splitting over the emerging nanostructured photocatalysts is often constrained by their surface electronic properties, which can lead to imbalance in redox reactions, reduced efficiency, and poor stability. We have investigated the impact of surface charge properties on the photocatalytic activity of InGaN nanowires. By optimizing the surface charge properties through controlled p-type dopant (Mg) incorporation, we have demonstrated an apparent quantum efficiency of ∼17.1% and ∼12.3% for InGaN nanowire arrays under visible light irradiation (400 nm–490 nm) in aqueous methanol and in the overall neutral-pH water splitting reaction, respectively.

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“…AlN, GaN and InN all crystallize in the wurtzite structure, but have vastly different band gaps ranging from 6.0 eV for AlN down to 0.7 eV for InN. For light emitting diodes (LEDs) 1 and laser diodes (LDs) 2,3 the group-III-nitrides are currently the only commercially available materials class for the green to the deep ultraviolet part of the spectrum, and future applications as chemical sensors, 4 in quantum cryptography 5 or in photocatalysis 6 are being explored. Applications in solid state lighting, however, are currently limited by loss mechanisms 7,8 and a deeper understanding of the fundamental materials properties is required.…”

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Strain effects in group-III nitrides: Deformation potentials for AlN, GaN, and InN

Yan

Rinke

Scheffler

et al. 2009

Applied Physics Letters

161

120

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A systematic density functional theory (DFT) study of strain effects on the electronic band structure of the group-III nitrides (AlN, GaN and InN) is presented. To overcome the deficiencies of the local-density and generalized gradient approximations (LDA and GGA) the Heyd-Scuseria-Ernzerhof hybrid functional (HSE) is used. Cross-checks for GaN demonstrate good agreement between HSE and exact-exchange based G0W0 calculations. We observe a pronounced nonlinear dependence of band-energy differences on strain. For realistic strain conditions in the linear regime around the experimental equilibrium volume a consistent and complete set of deformation potentials is derived.PACS numbers: 71.20. Nr, 71.70.Fk, 85.60.Bt The group-III nitride compounds and their alloys have recently received considerable attention as a versatile materials class. AlN, GaN and InN all crystallize in the wurtzite structure, but have vastly different band gaps ranging from 6.0 eV for AlN down to 0.7 eV for InN. For light emitting diodes (LEDs) 1 and laser diodes (LDs) 2,3 the group-III-nitrides are currently the only commercially available materials class for the green to the deep ultraviolet part of the spectrum, and future applications as chemical sensors, 4 in quantum cryptography 5 or in photocatalysis 6 are being explored. Applications in solid state lighting, however, are currently limited by loss mechanisms 7,8 and a deeper understanding of the fundamental materials properties is required. One crucial factor is the effect of strain.Due to the large differences in lattice parameters and thermal expansion coefficients between the substrate and the nitride overlayers, and between nitride layers with different alloy compositions, strain is always present in group-III-nitride based devices. Strain influences the optical properties, 9-11 in particular the energy of optical transitions, and for nonpolar or semipolar devices the polarization of the emitted light. 12 The effects of strain are characterized by the change of a transition energy (energy difference) upon application of strain, and the linear coefficient is defined as deformation potential. Together with the Luttinger (band) parameters, the deformation potentials constitute essential input for device modeling. 13 The experimental determination of deformation potentials is quite difficult, and aggravated by the fact that not all strain components can be determined accurately or without further approximations and that the deformation potentials cannot be isolated from each other, because uniaxial and biaxial strain cannot be applied separately. As a result the experimental data for GaN are scattered over a very large range. 10,11,14-17 For AlN and InN no experimental data are available, except for the hydrostatic deformation potential of the band gap in InN. 18 Previous theoretical studies have also produced widely differing values, resulting in a large uncertainty range. [19][20][21] The error bars can, in part, be attributed to the band-gap problem of density functional theory (DF...

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Photocatalysis Using GaN Nanowires

Cited by 191 publications

References 12 publications

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

Si/InGaN Core/Shell Hierarchical Nanowire Arrays and their Photoelectrochemical Properties

Group III-nitride nanowire structures for photocatalytic hydrogen evolution under visible light irradiation

Strain effects in group-III nitrides: Deformation potentials for AlN, GaN, and InN

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