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Journal ArticleDOI

Oxygen defective metal oxides for energy conversion and storage

TL;DR: In this article, the authors present an overview of progress made in preparing oxygen defective metal oxide nanostructures and probing the role of oxygen vacancies on the performance of metal oxides.
About: This article is published in Nano Today.The article was published on 2017-04-01. It has received 242 citations till now. The article focuses on the topics: Oxide & Water splitting.
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Journal ArticleDOI
TL;DR: The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches and can yield spinels with improved ORR/OER catalytic activities, which can further accelerate the speed, prolong the life, and narrow the polarization of fuel cells, metal-air batteries, and water splitting devices.
Abstract: Spinels with the formula of AB2O4 (where A and B are metal ions) and the properties of magnetism, optics, electricity, and catalysis have taken significant roles in applications of data storage, biotechnology, electronics, laser, sensor, conversion reaction, and energy storage/conversion, which largely depend on their precise structures and compositions. In this review, various spinels with controlled preparations and their applications in oxygen reduction/evolution reaction (ORR/OER) and beyond are summarized. First, the composition and structure of spinels are introduced. Then, recent advances in the preparation of spinels with solid-, solution-, and vapor-phase methods are summarized, and new methods are particularly highlighted. The physicochemical characteristics of spinels such as their compositions, structures, morphologies, defects, and substrates have been rationally regulated through various approaches. This regulation can yield spinels with improved ORR/OER catalytic activities, which can furth...

1,036 citations

Journal ArticleDOI
TL;DR: This article summarizes the major challenges and some invigorating perspectives for future research on crystal facet engineered photoelectrodes, which are believed to play a vital role in promoting the development of this important research field.
Abstract: Photoelectrochemical (PEC) water splitting is a promising approach for solar-driven hydrogen production with zero emissions, and it has been intensively studied over the past decades. However, the solar-to-hydrogen (STH) efficiencies of the current PEC systems are still far from the 10% target needed for practical application. The development of efficient photoelectrodes in PEC systems holds the key to achieving high STH efficiencies. In recent years, crystal facet engineering has emerged as an important strategy in designing efficient photoelectrodes for PEC water splitting, which has yet to be comprehensively reviewed and is the main focus of this article. After the Introduction, the second section of this review concisely introduces the mechanisms of crystal facet engineering. The subsequent section provides a snapshot of the unique facet-dependent properties of some semiconductor crystals including surface electronic structures, redox reaction sites, surface built-in electric fields, molecular adsorption, photoreaction activity, photocorrosion resistance, and electrical conductivity. Then, the methods for fabricating photoelectrodes with faceted semiconductor crystals are reviewed, with a focus on the preparation processes. In addition, the notable advantages of the crystal facet engineering of photoelectrodes in terms of light harvesting, charge separation and transfer, and surface reactions are critically discussed. This is followed by a systematic overview of the modification strategies of faceted photoelectrodes to further enhance the PEC performance. The last section summarizes the major challenges and some invigorating perspectives for future research on crystal facet engineered photoelectrodes, which are believed to play a vital role in promoting the development of this important research field.

449 citations

Journal ArticleDOI
26 Mar 2018-ACS Nano
TL;DR: A morphology and phase-controlled electrodeposition of MnO2 with ultrahigh mass loading of 10 mg cm-2 on a carbon cloth substrate is performed to achieve high overall capacitance without sacrificing the electrochemical performance.
Abstract: Metal oxides have attracted renewed interest as promising electrode materials for high energy density supercapacitors. However, the electrochemical performance of metal oxide materials deteriorates significantly with the increase of mass loading due to their moderate electronic and ionic conductivities. This limits their practical energy. Herein, we perform a morphology and phase-controlled electrodeposition of MnO2 with ultrahigh mass loading of 10 mg cm–2 on a carbon cloth substrate to achieve high overall capacitance without sacrificing the electrochemical performance. Under optimum conditions, a hierarchical nanostructured architecture was constructed by interconnection of primary two-dimensional e-MnO2 nanosheets and secondary one-dimensional α-MnO2 nanorod arrays. The specific hetero-nanostructures ensure facile ionic and electric transport in the entire electrode and maintain the structure stability during cycling. The hierarchically structured MnO2 electrode with high mass loading yields an outsta...

405 citations

Journal ArticleDOI
TL;DR: In this article, the type, regulation strategy, fine defect characterization methods, and their application in the electrocatalytic CO2 reduction reaction (CRR) and N 2 reduction reaction(NRR) are discussed and summarized, and major challenges, opportunities, and future development direction of defect engineering in CRR and NRR catalysts are proposed.
Abstract: The electrocatalytic CO2 reduction reaction (CRR) and N2 reduction reaction (NRR), which convert inert small molecules into high-value products under mild conditions, have received much research attention Defect engineering is an important strategy for modulating the electronic properties of electrocatalysts, which may endow unexpected physical and chemical properties to break the intrinsic bottleneck and, therefore, boost the electrocatalytic performance To date, various defective nanomaterials (such as nanocarbon and transition metal compounds) have been synthesized that display great potential for the CRR and NRR Therefore, a deep understanding of the influence of defects on the catalytic activity is urgently needed In this review, the type, regulation strategy, fine defect characterization methods, and their application in the electrocatalytic CRR and NRR are discussed and summarized Furthermore, the major challenges, opportunities, and future development direction of defect engineering in CRR and NRR catalysts are proposed This review aims to provide a reference for the proof-of-concept design of highly active CRR and NRR electrocatalysts

392 citations

References
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Journal ArticleDOI
07 Jul 1972-Nature
TL;DR: Water photolysis is investigated by exploiting the fact that water is transparent to visible light and cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm.
Abstract: ALTHOUGH the possibility of water photolysis has been investigated by many workers, a useful method has only now been developed. Because water is transparent to visible light it cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm (ref. 1).

27,819 citations

Journal ArticleDOI
24 Oct 1991-Nature
TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

26,457 citations

Journal Article
01 Jan 2001-Nature
TL;DR: In this paper, the authors look into the historical background, and present status and development prospects for photoelectrochemical cells, based on nanocrystalline materials and conducting polymer films.
Abstract: Until now, photovoltaics - the conversion of sunlight to electrical power - has been dominated by solid-state junction devices, often made of silicon. But this dominance is now being challenged by the emergence of a new generation of photovoltaic cells, based, for example, on nanocrystalline materials and conducting polymer films. These offer the prospect of cheap fabrication together with other attractive features, such as flexibility. The phenomenal recent progress in fabricating and characterizing nanocrystalline materials has opened up whole new vistas of opportunity. Contrary to expectation, some of the new devices have strikingly high conversion efficiencies, which compete with those of conventional devices. Here I look into the historical background, and present status and development prospects for this new generation of photoelectrochemical cells.

8,305 citations

Journal ArticleDOI
TL;DR: The biggest challenge is whether or not the goals need to be met to fully utilize solar energy for the global energy demand can be met in a costeffective way on the terawatt scale.
Abstract: Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2

8,037 citations

Journal ArticleDOI
TL;DR: Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting and its Applications d0 Metal Oxide Photocatalysts 6518 4.4.1.
Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

6,332 citations