Energy-related Areas Research Articles

Fabrication of directly 2D Z-scheme CuTiO3/g-C3N4 with high photocatalytic activities for CO2 reduction and hydrogen production

Photocatalysts based on Z-scheme heterostructure have been extensively investigated for CO2 reduction and hydrogen production, which solve the problem of high electron-hole pair complexation and low reduction and oxidation capacity in photocatalysts. Here, two-dimensional CuTiO3/g-C3N4 (CTO/CN) photocatalysts with directly Z-scheme heterostructure are prepared by effective manipulation of different components of CuTiO3 (CTO) nanoparticles on 2D (two-dimension) porous g-C3N4 (CN) nanosheets via in-situ growing strategy. Benefited from the special electronic structure, it demonstrates that the 4.0 % CTO/CN sample has an excellent photocatalytic activity for the reduction of CO2 to H2 (at a speed of 19.56 μmol g−1 h−1) and CO (at a speed of 19.93 μmol g−1 h−1), which are upper than those of pure g-C3N4 by 43.5 and 17.1 times, respectively. Furthermore, the 4.0 % CTO/CN sample exhibits utstanding performance in electrocatalytic hydrogen production. This synthetic strategy is useful for constructing a 2D Z-scheme heterostructure for applications in energy-related areas.

Multifunctional Electrochromic Devices for Energy Applications

A lot of development in terms of science and technology has taken place to address the increasing energy needs. This demand is expected to increase, especially due to environmental concerns associated with fossil fuels which have led to aggressive research toward energy storage materials and devices. Looking at this emerging trend, devices and materials that can convert, store, and save energy are the need of the hour. Electrochromic devices that assimilate these energy functionalities, along with bias-induced color modulation, are very promising as they not only help in energy conversion and storage but also help in energy saving when used as smart e-curtains for application in buildings and vehicles. The current Focus Review describes the promise of multifunctional electrochromic devices which can convert/generate and store energy through operations similar to batteries and supercapacitors. It also explains how electrochromism can prove to be a breakthrough in energy-related areas along with key challenges.

Substitutional doping of MoTe2/ZrS2 heterostructures for sustainable energy related applications.

Stacking and/or substitutional doping are effective strategies to tune two-dimensional materials with desired properties, greatly extending the applications of the pristine materials. Here, by employing first-principles calculations, we propose that a pristine MoTe2/ZrS2 heterostructure is a distinguished lithium-ion battery anode material with a low Li diffusion barrier (∼0.26 eV), and it has a high maximum Li storage capacity (476.36 mA h g-1) and a relatively low open-circuit voltage (0.16 V) at Li4/MoTe2/Li/ZrS2/Li4. The other heterostructures with different types can be achieved by substitutional doping and their potential applications in sustainable energy related areas are further unraveled. For instance, a type-II TeMoSe/ZrS2 heterostructure could be a potential direct Z-scheme photocatalyst for water splitting with a high solar-to-hydrogen conversion efficiency of 17.62%. The TeMoSe/SZrO heterostructure is predicted to be a potential candidate for application in highly efficient solar cells. Its maximum power conversion efficiency can be as high as 19.21%, which is quite promising for commercial applications. The present results will shed light on the sustainable energy applications of pristine or doped MoTe2/ZrS2 heterostructures in the future.

A robust in-situ catalytic graphitization combined with salt-template strategy towards fast lithium-ions storage

Lithium-ion hybrid supercapacitors (LIHSs) have received significant attention in electrochemical energy-related areas. However, the sluggish anode kinetics hinders the improvement of power density and cycling stability. Herein, an in-situ catalytic graphitization with a salt-template strategy was applied to prepare the porous graphitic carbon nanosheets. The results demonstrated that the addition of KCl led to a higher specific surface area and higher porous structure. The as-prepared potassium-induced porous graphitic carbon flakes (PPGCs) exhibited an electrochemical plateau capacity of 240.1 mAh g −1 and an electrochemical slope capacity of 129.0 mAh g −1 . PPGCs also delivered superior rate performance of 60.8 mAh g −1 even at 5.0 A g −1 , which was much better than graphitic carbon flakes (GCFs) and potassium-induced graphitic carbon flakes (PGCFs). When assembled into LIHSs devices with commercial activated carbon, the energy density reached 75.6 Wh kg −1 , and the power density was as high as 5.05 kW kg −1 . After 10,000 cycles at 5.0 A g −1 , the energy density was maintained at 39.2 Wh kg −1 , revealing excellent long-term cycling performance. This work may provide a promising solution to obtain graphitic carbon with a high graphitization degree and highly porous structure. • In-situ catalytic graphitization incorporated into salt-template strategy was developed. • Porous graphene-like graphitic carbon nanosheets were achieved successfully. • The effect of KCl added before and after hydrothermal procedure was illustrated. • The energy density reached 75.6 Wh kg −1 with 68.4% retention after 10,000 cycles.

New Approach toward Dual-Emissive Organic-Inorganic Hybrids by Integrating Mn(II) and Cu(I) Emission Centers in Ionic Crystals.

Inorganic-organic hybrid luminescent materials have received great attention for their potential applications in a wide range of clean/renewable energy-related areas, including photovoltaics and solid-state lighting. Herein, we present a unique and general "Mn + Cu" approach by blending two earth-abundant luminogenic metals, manganese and copper, within a single ionic structure to construct a remarkable family of low-cost and multifunctional hybrid materials featuring dual emission, as well as triboluminescence and second-harmonic generation response. The novel hybrid materials are made of diphosphine dioxide-chelated [Mn(O∧O)3]2+ cations and various anionic [CuxIy](y-x)- clusters, ensuring manifestation of dual phosphorescence streamed from octahedral Mn2+ ions (605-648 nm) and iodocuprate anions (480-728 nm). Noteworthily, the relative ratio of the emission bands, and hence a resulting emission chromaticity, can be tuned in a wide range through modification of cluster [CuxIy](y-x)- modules. The structural diversity, enhanced robustness, and up to 100% luminescence quantum yield make the designed materials promising phosphors for lighting and sensing applications.

A comprehensive review on applications of multicriteria decision‐making methods in power and energy systems

Energy has been considered as one of the essential needs of mankind along with air, water, and food and witnessed evolution of civilization since evidence of human life. Managing energy resources is one of the challenging problems being capital intensive. Addressing this involves critical thinking and decision making with all possible aspects, technically known as set of primary and secondary criteria. There exist a number of literature sources addressing applications of multicriteria decision-making (MCDM) in different energy-related areas. Some are focusing on energy policy making, few are explaining site selection of solar PV, wind farm, and hydro power plants, and a few are describing applications in load management. Moreover, a few literature in this field elaborates various MCDM methods and their applications. In this article, an extensive and exhaustive study is carried out incorporating almost all possible applications of MCDM in renewable energy area. Various energy-intensive applications are mapped with MCDM methods along with governing sensitive parameters. Hence, this study facilitates practicing engineers, decision-makers, academician, and researchers to identify areas and MCDM techniques researched over the past decade in energy sector for planning, managing, selecting renewable resources, etc.

Highly Stable Trimetallic (Co, Ni, and Fe) Zeolite Imidazolate Framework Microfibers: An Excellent Electrocatalyst for Water Oxidation

One dimensional (1D) metal organic framework (MOF) micro/nanostructural arrays are highly promising candidates for their potential applications in energy related areas. These exceptional behaviors ...

Making Use of Evaluations to Support a Transition towards a More Sustainable Energy System and Society—An Assessment of Current and Potential Use among Swedish State Agencies

Evaluations hold the potential to support decision-making so that current global challenges related to climate and energy can be addressed; however, as the challenges are becoming increasingly large and complex, new and transformative evaluation approaches are called for. Such transformative evaluation in turn builds on an extended and more deliberate use of evaluations. This study focuses on the current evaluation use practices among Swedish state agencies who are commissioning and/or conducting evaluations within climate and energy-related areas. Building on focus group sessions with four agencies and a structured interview questionnaire answered by representatives at five state agencies, the results shed light on how informants perceive the current practices of using evaluations, following the models of use presented in the evaluation literature. These results show perceived use as mainly instrumental or conceptual, along with showing an overall emphasis on models of use that are deemed constructive for moving towards transformative evaluations. The results also outline key benefits and challenges related to the adoption of a transformative evaluation approach. Such benefits include a more structured planning and use of evaluations, while challenges relate to institutional barriers and mandates to coordinate evaluations on a transformative scale.

Abundant heterointerfaces in MOF-derived hollow CoS2–MoS2 nanosheet array electrocatalysts for overall water splitting

A MOF-etching strategy is reported to design hierarchical hollow CoS 2 –MoS 2 heteronanosheet arrays. Due to the controllable etching of MOF by MoO 4 2− , the obtained CoS 2 –MoS 2 catalyst has abundant heterointerfaces for efficient HER and OER. • Hierarchical hollow CoS 2 –MoS 2 heteronanosheet arrays is fabricated. • The selective etching of MOF by MoO 4 2− can generate abundant heterointerfaces. • The engineered heterostructure exhibits small overpotentials for HER, OER. • A cell voltage of 1.56 V at 10 mA cm −2 can boost overall water splitting. Rational coupling of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts is extremely important for practical overall water splitting, but it is still challenging to construct such bifunctional heterostructures. Herein, we present a metal–organic framework (MOF)-etching strategy to design free-standing and hierarchical hollow CoS 2 –MoS 2 heteronanosheet arrays for both HER and OER. Resulting from the controllable etching of MOF by MoO 4 2− and in-situ sulfuration, the obtained CoS 2 –MoS 2 possesses abundant heterointerfaces with modulated local charge distribution, which promote water dissociation and rapid electrocatalytic kinetics. Moreover, the two-dimensional hollow array architecture can not only afford rich surface-active sites, but also facilitate the penetration of electrolytes and the release of evolved H 2 /O 2 bubbles. Consequently, the engineered CoS 2 –MoS 2 heterostructure exhibits small overpotentials of 82 mV for HER and 266 mV for OER at 10 mA cm −2 . The corresponding alkaline electrolyzer affords a cell voltage of 1.56 V at 10 mA cm −2 to boost overall water splitting, along with robust durability over 24 h, even surpassing the benchmark electrode couple composed of IrO 2 and Pt/C. The present work may provide valuable insights for developing MOF-derived heterogeneous electrocatalysts with tailored interface/surface structure for widespread application in catalysis and other energy-related areas.

TiO2 nanosheet/NiO nanorod hierarchical nanostructures: p–n heterojunctions towards efficient photocatalysis

TiO2 nanosheet/NiO nanorod heterojunction hybrids have been developed through a hydrothermal route, where NiO nanorods (size: 5 nm in diameter and 20–40 nm in length) are deposited at the {0 0 1} facet of anatase TiO2 nanosheets. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy and time-resolved fluorescence. The TiO2/NiO photocatalysts exhibited good photocatalytic activities towards the degradation of methyl blue (MB) and phenol, and hydrogen generation efficiency under visible light irradiation. The maximum rate constant can be reached 0.0279 min−1 and 0.0135 min−1 respectively, which are about 12 and 10 times higher than that of TiO2 nanosheets. And the hydrogen generation efficiency is 10 times higher than physical mixing of TiO2 and NiO. Photocatalytic degradation efficiency remains more than 90% after 6 times cycle dye degradation, and the H2 production efficiency is almost the same after four cycles, suggesting good stability and reusability. The enhanced photocatalytic activities are associated with the rational design of TiO2/NiO hierarchical heterojunctions which ensues high photogenerated charge separation efficiency. With the improved photocatalytic performance, the TiO2/NiO heterojunction hybrids are expected to be potential photocatalysts in environmental and energy related areas.

Form-stable phase change materials based on delignified wood flour for thermal management of buildings

In this work, form-stable phase change composites (PCCs) was prepared based on wood flour (WF), the by-product of timber industry, via delignification and impregnation with myristyl alcohol (MA). After delignification, the micro-channel structure inherited from wood was still maintained and unblocked in delignified wood flour (dWF), which are beneficial to accommodate and restrict solid-liquid phase change materials (PCMs). The dWF/MA PCCs exhibit excellent leakage-proof properties even at temperature much higher than the melting point of MA and high phase change enthalpy. The dWF/MA PCCs were further used to fabricate composite boards by bonding with urea–formaldehyde (UF) resin. The temperature management effect of dWF/MA/UF boards was tentatively demonstrated through constructing building models and measuring the inner temperature-time curves. This work provides a promising way to fully utilize and functionalize WF and broad its application in energy-related areas.

Recent Progress of In Situ Transmission Electron Microscopy for Energy Materials

In situ transmission electron microscopy (TEM) is one of the most powerful approaches for revealing physical and chemical process dynamics at atomic resolutions. The most recent developments for in situ TEM techniques are summarized; in particular, how they enable visualization of various events, measure properties, and solve problems in the field of energy by revealing detailed mechanisms at the nanoscale. Related applications include rechargeable batteries such as Li-ion, Na-ion, Li-O2 , Na-O2 , Li-S, etc., fuel cells, thermoelectrics, photovoltaics, and photocatalysis. To promote various applications, the methods of introducing the in situ stimuli of heating, cooling, electrical biasing, light illumination, and liquid and gas environments are discussed. The progress of recent in situ TEM in energy applications should inspire future research on new energy materials in diverse energy-related areas.

Mechanically robust and self-cleaning antireflection coatings from nanoscale binding of hydrophobic silica nanoparticles

Antireflection coatings from silica nanoparticles exhibit promising applications in many energy-related areas such as solar-thermal and photo-voltaic systems. However, the coatings suffer from poor mechanical durability and low self-cleaning capability in outdoor conditions, which limit their practical application. Here, we create mechanically robust and self-cleaning antireflection coatings through nanoscale binding of hydrophobic silica nanoparticles with an organosilica binder. The coatings demonstrated nearly full transmission at desired wavelength of ∼550 nm, with peak transmittance up to 99.9%. Further advantage of these coatings is the combination of hydrophobic silica nanoparticles with the organosilica binder, resulting in hydrophobic and mechanically robust coatings, with water contact angle of 161° and hardness of 4.2 GPa. The coatings maintained their high transmittance under outdoor conditions for 3 months, which is largely attributed to their self-cleaning functionality resulting from super-hydrophobicity. We envision that the mechanically robust and self-cleaning antireflection coatings could find wide applications in outdoor conditions and other harsh environments.

III-VI van der Waals heterostructures for sustainable energy related applications.

van der Waals (vdW) heterostructures, achieved by binding various two-dimensional (2D) materials together via vdW interaction, expand the family of 2D materials and show fascinating possibilities. In this work, we have systematically investigated the geometrical structures, electronic structures, and optical properties of III-VI (MX, M = Ga, In and X = S, Se, Te) vdW heterostructures and their corresponding applications in sustainable energy related areas based on first principles calculations. It is highlighted that different heterostructure types can be achieved in spite of the similar electronic structures of MX monolayers. Meanwhile, the potential applications of the heterostructures for sustainable energy related areas have been further unraveled. For instance, type-II InS/GaSe and GaS/GaSe vdW heterostructures can separately produce hydrogen and oxygen at the opposite parts. On the other hand, a type-II GaSe/GaTe heterostructure with a direct band gap compatible with silicon has been proposed to be a potential solar cell material with a power conversion efficiency over 18%. Furthermore, a gapless type-IV semi-metallic InTe/GaS heterostructure has been predicted to be a Li-ion battery anode material based on three-step lithiated analysis. The present results will shed light on the sustainable energy applications of such remarkable artificial MX vdW heterostructures in the future.

Large area ultra-thin graphene films for functional photovoltaic devices

Abstract

A Facile Method for Loading CeO2 Nanoparticles on Anodic TiO2 Nanotube Arrays

In this paper, a facile method was proposed to load CeO2 nanoparticles (NPs) on anodic TiO2 nanotube (NT) arrays, which leads to a formation of CeO2/TiO2 heterojunctions. Highly ordered anatase phase TiO2 NT arrays were fabricated by using anodic oxidation method, then these individual TiO2 NTs were used as tiny “nano-containers” to load a small amount of Ce(NO3)3 solutions. The loaded anodic TiO2 NTs were baked and heated to a high temperature of 450 °C, under which the Ce(NO3)3 would be thermally decomposed inside those nano-containers. After the thermal decomposition of Ce(NO3)3, cubic crystal CeO2 NPs were obtained and successfully loaded into the anodic TiO2 NT arrays. The prepared CeO2/TiO2 heterojunction structures were characterized by a variety of analytical technologies, including XRD, SEM, and Raman spectra. This study provides a facile approach to prepare CeO2/TiO2 films, which could be very useful for environmental and energy-related areas.

Mechanism of Carbon Dioxide and Water Incorporation in Ba2TiO4: A Joint Computational and Experimental Study

CO2 incorporation in solids is attracting considerable interest in a range of energy-related areas. Materials degradation through CO2 incorporation is also a critical problem with some fuel cell materials, particularly for proton conducting ceramic fuel cells. Despite this importance, the fundamental understanding of the mechanism of CO2 incorporation is lacking. Furthermore, the growing use of lower temperature sol gel routes for the design and synthesis of new functional materials may be unwittingly introducing significant residual carbonate and hydroxyl ions into the material, and so studies such as the one reported here investigating the incorporation of carbonate and hydroxyl ions are important, to help explain how this may affect the structure and properties. This study on Ba2TiO4 suggests highly unfavorable intrinsic defect formation energies but comparatively low H2O and CO2 incorporation energies, in accord with experimental findings. Carbonate defects are likely to form in both pristine and undo...

Quantum Dots of 1T Phase Transitional Metal Dichalcogenides Generated via Electrochemical Li Intercalation.

We prepare group VI transitional metal dichalcogenides (TMDs, or MX2) from the 1T phase with quantum-sized and monolayer features via a quasi-full electrochemical process. The resulting two-dimensional (2D) MX2 (M = W, Mo; X = S, Se) quantum dots (QDs) are ca. 3.0-5.4 nm in size with a high 1T phase fraction of ca. 92%-97%. We attribute this to the high Li content intercalated in the 1T-MX2 lattice (mole ratio of Li:M is over 2:1), which is achieved by an increased lithiation driving force and a reduced electrochemical lithiation rate (0.001 A/g). The high Li content not only promotes the 2H → 1T phase transition but also generates significant inner stress that facilitates lattice breaking for MX2 crystals. Because of their high proportion of metallic 1T phase and sufficient active sites induced by the small lateral size, the 2D 1T-MoS2 QDs show excellent hydrogen evolution reactivity (with a typical η10 of 92 mV, Tafel slope of 44 mV/dec, and J0 of 4.16 × 10-4 A/cm2). This electrochemical route toward 2D QDs might help boost the development of 2D materials in energy-related areas.

Clean Power Generation from the Intractable Natural Coalfield Fires: Turn Harm into Benefit

The coal fires, a global catastrophe for hundreds of years, have been proved extremely difficult to control, and hit almost every coal-bearing area globally. Meanwhile, underground coal fires contain tremendous reservoir of geothermal energy. Approximately one billion tons of coal burns underground annually in the world, which could generate ~1000 GW per annum. A game-changing approach, environmentally sound thermal energy extraction from the intractable natural coalfield fires, is being developed by utilizing the waste energy and reducing the temperature of coalfield fires at the same time. Based on the Seebeck effect of thermoelectric materials, the temperature difference between the heat medium and cooling medium was employed to directly convert thermal energy into clean electrical energy. By the time of December 2016, the power generation from a single borehole at Daquan Lake fire district in Xinjiang has been exceeded 174.6 W. The field trial demonstrates that it is possible to exploit and utilize the waste heat resources in the treated coal fire areas. It promises a significant impact on the structure of global energy generation and can also promote progress in thermoelectric conversion materials, geothermal exploration, underground coal fires control and other energy related areas.

Hierarchical flower-like carbon nanosheet assembly with embedded hollow NiCo2O4 nanoparticles for high- performance lithium ion batteries

The fabrication of closely bounded metal oxides/carbon hybrid nano-structures is significant for its use in energy-related areas especially lithium ion batteries (LIBs). In this research, a flower-like carbon sphere with hollow NiCo2O4 nanoparticles encapsulated inside the carbon thin nanopetal is fabricated by using a mixed basic carbonate nickel and cobalt sphere as the precursor and templates followed by the outer carbon membrane covering and two-step calcination process. When tested as anode material for LIBs, this flower-like carbon-based hybrid sphere demonstrates a significantly enhanced reversible capacity and cycling stability at various current densities.