N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

Wang, Meng; Ren, Feng; Zhou, Jigang; Cai, Guangxu; Cai, Li; Hu, Yongfeng; Wang, Dongniu; Liu, Yichao; Guo, Liejin; Shen, Shaohua

doi:10.1038/srep12925

Cited by 201 publications

(140 citation statements)

References 48 publications

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“…In ZnO Raman spectrum, peak at ∼438 cm −1 can be assigned to a nonpolar E2 (high) optical phonon mode that corresponds to the band characteristics of wurtzite hexagonal phase of ZnO. 28,29 The peak at ∼380 cm −1 is due to the A1 (TO) mode, whereas, peaks around 202 and 330 cm −1 are due to resonance conditions and can be assigned to acoustic phonon overtone and optical phonon overtone modes with A1 symmetry, respectively. 30 Moreover, the broad peak around 1145 cm −1 belongs to the Raman 2LO mode.…”

Section: Resultsmentioning

confidence: 99%

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor

Sarkar

Das

Sharada

et al. 2017

J. Electrochem. Soc.

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A novel core-shell design for nano-structured electrode materials is introduced for realizing cost-effective and high-performance supercapacitors. In the proposed core-shell design, thin shell-layers of highly pseudo-capacitive materials provide the platform for surface or near-surface-based faradaic and non-faradaic reactions together with shortened ion-diffusion path facilitating fast-ion intercalation and deintercalation processes. The highly-conducting core serves as highway for fast electron transfer toward current collectors, improving both energy and power performance characteristics of the core-shell structure in relation to pristine component materials. Furthermore, use of carbon (C)-based materials as a shell layer in either electrode not only enhances capacitive performance through double-layer formation but also provides enough mechanical strength to sustain volume changes in the core material during long-cycling of the supercapacitor improving its cycle life. In order to enhance electrochemical performance in terms of specific capacitance and rate capability via core-shell architecture and nano-structuring, an asymmetric supercapacitor (ASC) is assembled using ZnO/α-Fe 2 O 3 and ZnO/C core-shell nanorods as respective negative and positive electrodes. The ASC exhibits a specific capacitance of ∼115 F/g at a scan rate of 10 mV/s in a potential window as large as 1.8 V with a response time as short as ∼39 ms and retains more than 80% of its initial capacitance after 4000 cycles. Interestingly, the ASC can deliver an energy density of ∼41 Wh/kg and a power density of ∼7 kW/kg that are significantly higher than those reported hitherto for iron-oxide-based ASCs. Global concern over ever increasing greenhouse gas emissions owing to exorbitant anthropogenic usage of fossil fuels is forcing governments across the globe to swing toward renewable energy sources. Since renewable sources of energy, like sun and wind, are intermittent in nature, it becomes mandatory to store the energy from these sources that could be retrieved on demand. Accordingly, the missing link in successful exploitation of renewable energy is its storage. 1Electrochemical storage of energy in storage-batteries is attractive but supercapacitors are gaining attention due to their compelling power densities as well as fast charge and discharge traits. 2,3 It is noteworthy that a battery is an energy device while a supercapacitor is a power device. If we require high power from a battery, we will generally extract less total energy than if we require low power. Supercapacitors can complement battery-power by allowing rapid charge and discharge cycles. Accordingly, supercapacitors complement batteries perfectly in the emerging energy-storage landscape and therefore the usage of a battery-supercapacitor hybrid structure is not only becoming increasingly common, but also inevitable.In the light of the foregoing, we have attempted to develop a high-performance asymmetric supercapacitor (ASC) using onedimensional (1-D) core-shell nanorods (NRs) e...

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Section: Resultsmentioning

confidence: 99%

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor

Sarkar

Das

Sharada

et al. 2017

J. Electrochem. Soc.

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“…The valence band of TiO 2 and ZnO (mostly from O 2p orbitals) is quite deep, ≈1.6-1.7 V, more positive than the O 2 /H 2 O potential, while the conduction band (mainly from Ti 3d or Zn 3d) is only barely more negative than the H 2 O/H 2 potential. [142,220] However, the low solubility of these 2p and 3p anions in TiO 2 and ZnO as well as the unbalanced charges created from the replacement of O 2− by these anions (e.g., C 4− , N 3− ) and their associated recombination limits both optical absorption and charge collection efficiencies of materials. Typically, this could be done by doping TiO 2 and ZnO with some 2p or 3p anions with higher atomic p orbital energies than that of O, such as C, N, S, and P. [219] Hoang et al demonstrated that incorporating N into TiO 2 NW arrays by annealing TiO 2 NWs in NH 3 flow can lower the band gap of TiO 2 to ≈2.4 eV.…”

Section: Photocatalytic Water Splittingmentioning

confidence: 99%

Nanowire Array Structures for Photocatalytic Energy Conversion and Utilization: A Review of Design Concepts, Assembly and Integration, and Function Enabling

Hoang

Gao

2016

Advanced Energy Materials

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Environmental pollution and the shortage of clean and renewable energy resources are two of the grand challenges the world is facing today. [1] Photocatalysis is one active research area toward the effort of conversion and utilization of sunlight energy to solve these challenges with annual publication of more than 2000 peer-reviewed papers. [2] Photocatalysis finds its potential applications in the direct conversion of sunlight energy into electricity and fuels (hydrogen, hydrocarbons) using photoelectrochemical (PEC) solar cells (dye-sensitized/ quantum-dot-sensitized solar cells) [3][4][5] and photocatalytic waterThe increasing human demand for clean and renewable energy and a cleaner environment has stimulated various materials related research and development for efficient solar energy conversion and utilization, photocatalytic environmental remediation, and photoassisted selective conversion of organic compounds. Among the various candidate solutions to improving the efficiency of these processes, semiconductor nanowire (NW) and nanorod (NR) array structures have been offering a unique tool box combining desirable characteristics in structure, function, and applicability. Efficient photocatalytic energy conversion requires excellent light absorption, readily charge separation, transport, and collection, as well as fast kinetics of interfacial reactions and mass transport of reactants. The long axis of the NW enables adequate light absorption, while the radical axis provides short electron-hole separation distance. Additionally, the NW arrays have relatively high surface area to facilitate interfacial kinetics while their open pore structure allows good mass transport properties. This study reviews the current status of research on NW and NR array structures of some most popular semiconducting materials for photocatalytic energy conversion and utilization including photocatalytic water splitting and CO 2 reduction/fixation, dye/quantum dot sensitized solar cells, and other photoassisted reactive applications such as pollutant degradation, selective conversion of organic compounds, and biological disinfection.

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“…Wang et al . studied solution‐based ZnO nanorod arrays modified by controlled N doping using an advanced ion‐implantation method . They subsequently utilized NW arrays as photoanodes for photoelectrochemical water splitting under visible‐light irradiation.…”

Section: Progress In Contemporary Researches Of Doped Zno Applicabilimentioning

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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N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

Cited by 201 publications

References 48 publications

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor

Nanowire Array Structures for Photocatalytic Energy Conversion and Utilization: A Review of Design Concepts, Assembly and Integration, and Function Enabling

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

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N Doping to ZnO Nanorods for Photoelectrochemical Water Splitting under Visible Light: Engineered Impurity Distribution and Terraced Band Structure

Cited by 201 publications

References 48 publications

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe2O3//ZnO/C Asymmetric Supercapacitor

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe2O3//ZnO/C Asymmetric Supercapacitor

Nanowire Array Structures for Photocatalytic Energy Conversion and Utilization: A Review of Design Concepts, Assembly and Integration, and Function Enabling

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

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A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor

A Cost-Effective and High-Performance Core-Shell-Nanorod-Based ZnO/α-Fe₂O₃//ZnO/C Asymmetric Supercapacitor