Effects of GaN Thin Layer on InGaN at Electrolyte-Semiconductor Interface for the Application of Photoelectrochemical Water Splitting

2012 ◽  
Vol 1387 ◽  
Author(s):  
Katsushi Fujii ◽  
Kayo Koike ◽  
Mika Atsumi ◽  
Takashi Itoh ◽  
Takenari Goto ◽  
...  
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Hydrogen Generation ◽  
Uv Light ◽  
Photocurrent Density ◽  
Crystal Quality ◽  
Band Edge ◽  
Tunneling Effect ◽  
Conduction Band Edge ◽  
Indium Composition

ABSTRACTPhotoelectrochemical properties of nitride semiconductors are paid attention due to their possibilities of water splitting by visible light absorption. However, the photocurrent density of InxGa1-xN, which absorbs visible light, is usually lower than that of GaN, which has larger band-gap and absorbing only UV light. The reasons of this are thought to be the band-edge position at the semiconductor-electrolyte interface and the crystal quality. The conduction band-edge decreases with increasing of indium composition and across the hydrogen generation energy at around the indium composition of 0.2. This means that the hydrogen generation ability decreases with increasing of indium composition. Low crystal quality is obtained because the lower growth temperature of InxGa1-xN than that of GaN to achieve the indium incorporation. In order to improve the photocurrent density, band-edge energy control and quantum tunneling effect are tried using the structure of thin GaN layer on InxGa1-xN here. The effect for the photocurrent densities is also discussed.

SURFACE-CHARGE-ENABLED PHOTOLYTIC HYDROGEN GENERATION IN V2O5·H2O/Au NANOCONJUGATES

MRS Advances ◽  
2016 ◽  
Vol 1 (46) ◽  
pp. 3121-3126
Author(s):  
Sunith Varghese ◽  
Charuksha Walgama ◽  
Mark Wilkins ◽  
Sadagopan Krishnan ◽  
Kaan Kalkan
Keyword(s):  
Surface Charge ◽  
Hydrogen Generation ◽  
Hydrogen Reduction ◽  
Energy Levels ◽  
Sol Gel ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Current Voltage ◽  
Negative Surface ◽  
Negative Surface Charge

ABSTRACTThe present work investigates sol-gel synthesized vanadium oxyhydrate (V2O5·H2O) nanowires decorated with Au nanoparticles as potential photolytic H2 generators. As determined by UV photoelectron and optical spectroscopies, the conduction band edge of V2O5·H2O lies 0.6 eV below standard H+ reduction potential, implying no H2 can be generated. On the contrary, as measured by gas chromatography, our nanoconjugates yield reproducible light-to-hydrogen conversion efficiency of 5.3%, for the first hour of photolysis under 470 nm excitation. To explain the observed hydrogen reduction, we have hypothesized the vanadia electron energy levels are raised by some negative surface charge. With the objective of validating this hypothesis, we have performed cyclic current-voltage measurements. The derived conduction and valence band edge energies are not only consistent with the optical band gaps, but also validate the hypothesized energy increase by 1.6 eV, respectively. The negative surface charge is also corroborated by the ζ-potential. Based on the measured pH of 2.4, we attribute the negative surface charge to Lewis acid nature of the nanowires, establishing dative bonding with OH−. The present work establishes the importance of surface charge in photoelectrochemical reactions, where it can be instrumental and enabling in photolytic fuel production.

Effect of Different Mineralizers on Luminescence Characteristic of ZnO Crystals by Hydrothermal Method

2013 ◽  
Vol 848 ◽  
pp. 302-306
Author(s):  
Wen Li Zheng ◽  
Wei Yang
Keyword(s):  
Visible Light ◽  
Hydrothermal Method ◽  
Fill Factor ◽  
Crystal Morphology ◽  
Uv Light ◽  
Crystal Defects ◽  
Band Edge ◽  
Luminescence Characteristic ◽  
Amount Of Substance ◽  
Band Edge Transition

A comparative study worked on crystal morphology and luminescence characteristic by hydrothermal method with mineralizer of 3 mol /L KOH, fill factor of 35%, under the condition of three kinds of mineralizers which included 3 mol /L KOH in sample 1, 3 mol /L KOH and 1 mol /L LiOH in sample 2, 3 mol /L KOH and CaO: Zn ( OH) 2 = 2% (amount of substance percentage). Nonpolar ZnO crystals were synthesized by adding proper proportion of CaO or LiOH,the speed of growth along c-axic was weakened obviously. The obtained ZnO crystals exposed more areas on the positive polar face c { 0001}. meanwhile,it exposed negative polar-c {000},positive pyramidal face + p { 101},negative pyramidal face-p {10} and hexagonal faces m {1010}. Only KOH or LiOH auxiliarily added,the emission spectrum was only visible light,no UV light from band edge transition, indicating that the crystal defects luminous center are numerous. A strong UV band emitting from band edge transition was in luminescent spectrumn of the prepared crystals by adding CaO,which indicated a decrease in defects luminous center.

scholarly journals Phase transition-induced band edge engineering of BiVO4 to split pure water under visible light

2015 ◽  
Vol 112 (45) ◽  
pp. 13774-13778 ◽  
Author(s):  
Won Jun Jo ◽  
Hyun Joon Kang ◽  
Ki-Jeong Kong ◽  
Yun Seog Lee ◽  
Hunmin Park ◽  
...  
Keyword(s):  
Phase Transition ◽  
Visible Light ◽  
Band Gap ◽  
Conduction Band ◽  
Density Functional ◽  
Density Functional Theory Calculation ◽  
Pure Water ◽  
Volume Growth ◽  
Band Edge ◽  
Conduction Band Edge

Through phase transition-induced band edge engineering by dual doping with In and Mo, a new greenish BiVO4 (Bi1-XInXV1-XMoXO4) is developed that has a larger band gap energy than the usual yellow scheelite monoclinic BiVO4 as well as a higher (more negative) conduction band than H+/H2 potential [0 VRHE (reversible hydrogen electrode) at pH 7]. Hence, it can extract H2 from pure water by visible light-driven overall water splitting without using any sacrificial reagents. The density functional theory calculation indicates that In3+/Mo6+ dual doping triggers partial phase transformation from pure monoclinic BiVO4 to a mixture of monoclinic BiVO4 and tetragonal BiVO4, which sequentially leads to unit cell volume growth, compressive lattice strain increase, conduction band edge uplift, and band gap widening.

scholarly journals On topological materials as photocatalysts for water splitting by visible light

2021 ◽  
Author(s):  
Ahmad Ranjbar ◽  
Hossein Mirhosseini ◽  
Thomas D Küehne
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Water Oxidation ◽  
Electronic Structures ◽  
Density Functional ◽  
Band Edge ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Hartree Fock ◽  
Topological Materials

Abstract We performed virtual materials screening to identify promising topological materials for photocatalytic water splitting under visible light irradiation. Topological compounds were screened based on band gap, band edge energy, and thermodynamics stability criteria. In addition, topological types for our final candidates were computed based on electronic structures calculated by means of hybrid density functional theory including exact Hartree-Fock exchange. Our final list contains materials which have band gaps between 1.0 eV and 2.7 eV in addition to band edge energies suitable for water oxidation and reduction. However, the topological types of these compounds calculated with the hybrid functional differ from those reported previously. To that end, we discuss the importance of computational methods for the calculation of atomic and electronic structures in materials screening processes.

Facile development of CoAl-LDHs/RGO nanocomposites as photocatalysts for efficient hydrogen generation from water splitting under visible-light irradiation

2019 ◽  
Vol 6 (7) ◽  
pp. 1753-1760 ◽  
Author(s):  
Anbu Kumaresan ◽  
Shuo Yang ◽  
Kun Zhao ◽  
Nafees Ahmad ◽  
Jiyu Zhou ◽  
...  
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Visible Light Irradiation ◽  
Hydrogen Generation ◽  
Light Irradiation

The facile development of CoAl-LDHs/RGO nanocomposites as photocatalysts for efficient hydrogen generation from water splitting under visible-light irradiation.

scholarly journals Hydrogen Production Improvement on Water Decomposition Through Internal Interfacial Charge Transfer in M3(PO4)2-M2P2O7 Mixed-Phase Catalyst (M = Co, Ni, and Cu)

Catalysts ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 602
Author(s):  
Junyeong Kim ◽  
Jun Neoung Heo ◽  
Jeong Yeon Do ◽  
Seog Joon Yoon ◽  
Youngsoo Kim ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Visible Light ◽  
Water Splitting ◽  
Hydrogen Generation ◽  
Light Response ◽  
Mixed Phase ◽  
Interface Charge ◽  
Production Improvement ◽  
Active Metal ◽  
Two Phases

In this study, three types of Nasicon-type materials, Co3(PO4)2-CO2P2O7, Ni3(PO4)2-Ni2P2O7, and Cu3(PO4)2-Cu2P2O7, were synthesized as mixed-phase catalysts (MPCs) for evaluating their potential as new photocatalytic candidates (called Co3(PO4)2-CO2P2O7mpc, Ni3(PO4)2-Ni2P2O7mpc, and Cu3(PO4)2-Cu2P2O7mpc herein). Based on various physical properties, it was confirmed that there are two phases, M3(PO4)2 and M2P2O7, in which a similar phase equilibrium energy coexists. These colored powders showed UV and visible light responses suitable to our aim of developing 365-nm light-response photocatalysts for overall water-splitting. The photocatalytic performance of Ni2(PO4)3-Ni2P2O7 MPC showed negligible or no activity toward H2 evolution. However, Co2(PO4)3-Co2P2O7 MPC and Cu3(PO4)2-Cu2P2O7 MPC were determined as interesting materials because of their ability to absorb visible light within a suitable band. Moreover, an internal interface charge transfer was suggested to occur that would lower the recombination rate of electrons and holes. For Cu3(PO4)2-Cu2P2O7 MPC, the charge separation between the electron and hole was advantageously achieved, a water-splitting reaction was promoted, and hydrogen generation was considerably increased. The performance of a catalyst depended on the nature of the active metal added. In addition, the performance of the catalyst was improved when electrons migrated between the inter-phases despite the lack of a heterojunction with other crystals.

scholarly journals Theoretical investigation on $$\hbox {BeN}_{{2}}$$ monolayer for an efficient bifunctional water splitting catalyst

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
M. R. Ashwin Kishore ◽  
R. Varunaa ◽  
Amirhossein Bayani ◽  
Karin Larsson
Keyword(s):  
Water Splitting ◽  
Valence Band ◽  
Conduction Band ◽  
Theoretical Investigation ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Band Edge ◽  
Conduction Band Edge ◽  
Substantial Impact ◽  
Solar Hydrogen Production

AbstractThe search for an active, stable, and abundant semiconductor-based bifunctional catalysts for solar hydrogen production will make a substantial impact on the sustainable development of the society that does not rely on fossil reserves. The photocatalytic water splitting mechanism on a $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer has here been investigated by using state-of-the-art density functional theory calculations. For all possible reaction intermediates, the calculated changes in Gibbs free energy showed that the oxygen evolution reaction will occur at, and above, the potential of 2.06 V (against the NHE) as all elementary steps are exergonic. In the case of the hydrogen evolution reaction, a potential of 0.52 V, or above, was required to make the reaction take place spontaneously. Interestingly, the calculated valence band edge and conduction band edge positions for a $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer are located at the potential of 2.60 V and 0.56 V, respectively. This indicates that the photo-generated holes in the valence band can oxidize water to oxygen, and the photo-generated electrons in the conduction band can spontaneously reduce water to hydrogen. Hence, the results from the present theoretical investigation show that the $$\hbox {BeN}_{{2}}$$ BeN 2 monolayer is an efficient bifunctional water-splitting catalyst, without the need for any co-catalyst.

Visible Light Driven Water Splitting in a Molecular Device with Unprecedentedly High Photocurrent Density

2013 ◽  
Vol 135 (11) ◽  
pp. 4219-4222 ◽  
Author(s):  
Yan Gao ◽  
Xin Ding ◽  
Jianhui Liu ◽  
Lei Wang ◽  
Zhongkai Lu ◽  
...  
Keyword(s):  
Visible Light ◽  
Water Splitting ◽  
Photocurrent Density ◽  
Molecular Device ◽  
Visible Light Driven

A solution-processed, mercaptoacetic acid-engineered CdSe quantum dot photocathode for efficient hydrogen production under visible light irradiation

2015 ◽  
Vol 8 (5) ◽  
pp. 1443-1449 ◽  
Author(s):  
Bin Liu ◽  
Xu-Bing Li ◽  
Yu-Ji Gao ◽  
Zhi-Jun Li ◽  
Qing-Yuan Meng ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Quantum Dot ◽  
Visible Light ◽  
Water Splitting ◽  
Visible Light Irradiation ◽  
Hydrogen Generation ◽  
Light Irradiation ◽  
Mercaptoacetic Acid ◽  
Cdse Quantum Dot ◽  
Neutral Water

We describe a simple, efficient and stable mercaptoacetic acid-engineered CdSe quantum dot photocathode for hydrogen generation by water-splitting from neutral water.

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