Hydrogen adsorption and storage using solid‐state materials is an area of much current research interest, and one of the major stumbling blocks in realizing the hydrogen economy. However, no material ...yet researched comes close to reaching the DOE 2015 targets of 9 wt% and 80 kg m−3 at this time. To increase the physisorption capacities of these materials, the heats of adsorption must be increased to ∼20 kJ mol−1. This can be accomplished by optimizing the material structure, creating more active species on the surface, or improving the interaction of the surface with hydrogen. The main focus of this progress report are recent advances in physisorption materials exhibiting higher heats of adsorption and better hydrogen adsorption at room temperature based on exploiting the Kubas model for hydrogen binding: (η2‐H2)–metal interaction. Both computational approaches and synthetic achievements will be discussed. Materials exploiting the Kubas interaction represent a median on the continuum between metal hydrides and physisorption materials, and are becoming increasingly important as researchers learn more about their applications to hydrogen storage problems.
There is much current interest in Kubas‐type hydrogen because it may provide suitable hydrogen binding energies for room temperature storage. This article focuses on both calculations and synthesis of many systems involving the Kubas interaction, including modified carbon materials, metal–acetylene complexes, modified polymers, metal organic frameworks, reduced mesoporous titania, and surface organometallic supported silica.
Among the main components of a smart city, the energy system plays a vital and core role in the transition towards a sustainable urban life. Furthermore, the utilization of renewable energy sources ...has been demonstrated as a significant contribution to reducing pollutant emissions and enhancing the quality of the living environment. Therefore, designing the energy systems based on clean and renewable criteria is considered a sustainable solution for smart cities. Indeed, the deep and rapid penetration of renewable energy-based technologies have been believed to very well fit into a smart city under various scales, this could supply a secure basis for a modern society with a low-carbon economy. In this review paper, the main components and roles of renewable energy resources (such as solar, wind, geothermal, hydropower, ocean, and biofuels) for the smart city were fully introduced. Besides, integrating the renewable sources form into the energy systems of smart cities was thoroughly analyzed on the basis of technical and economic criteria. Finally, existing challenges and future scenarios were also discussed in detail to clarify the progress and perspective of smart renewable energy systems for the smart city. In general, the integration of renewables into energy systems of the smart city is a sagacious perspective and solution aiming to achieve cleaner process and more sustainable development. However, the optimization issues of the energy system for integrating of renewable components, ensuring good stability, maximizing the operating range, and minimizing the investment costs should be critically evaluated in the future works.
•Designing tools and key criteria for smart renewable energy systems.•Efficiency and prospect of integrating renewables into energy system for smart city.•Existing problems and challenges for renewable-based energy system in smart city.•Future scenarios for the sustainable development of energy system in smart city.
This paper proposes Han-Kobayashi signaling (HKS), under which each pair of users decodes a common message to improve their throughput, for UAV-enabled multi-user communication. Given that only a ...single transmit antenna is used and thus there is no null space of users' channels for inserting an artificial noise that would effectively help to jam an eavesdropper without interfering the users' desired signals, a new information and artificial noise transfer scheme to address physical layer security (PLS) for the considered networks is investigated. Under this scheme, the UAV sends the confidential information to its users within a fraction of the time slot and sends the artificial noise within the remaining fraction. Accordingly, the problem of jointly optimizing the time-fraction, bandwidth and power allocation to maximize the users' worst secrecy throughput is formulated. New inner approximations are proposed for developing path-following algorithms for its computation. Simulation shows that the proposed information and artificial noise transfer enables not only HKS but also orthogonal multi-access and nonorthogonal multi-access to provide PLS for UAV-enabled communication even when the eavesdropper is in the best channel condition. HKS outperforms the other two schemes in terms of users' worst secrecy throughput.
The present work reports efficient electrochemical nanosensors for the sensitive monitoring of 4-nitrophenol (4-NP) in tomato samples using various biosynthesized silver nanoparticles (bio-AgNPs). ...Three different bio-AgNP types were synthesized using natural plant extracts, including green tea (GT) leaf, grapefruit peel (GP), and mangosteen peel (MP), aiming to investigate their effects on the formation of bio-AgNPs, as well as the analytical performance of 4-NP. Based on the obtained results, it was found that the phytochemical content in various plant extracts directly influenced the physicochemical parameters of the created bio-AgNPs, such as particle size, crystallinity, and distribution. More importantly, these parameters have decisive effects on the electrocatalytic activity, conductivity, and electrochemical sensing performance of electrodes modified with them for 4-NP detection. Among the three bio-AgNPs evaluated, the GT-AgNPs (using green tea leaf extract) with uniform shape, small size without aggregation, and high crystallinity showed the best analytical performance for 4-NP determination. The electrode-modified GT-AgNPs exhibited a good 4-NP analytical performance with an electrochemical sensitivity of 1.25 μA μM
−1
cm
−2
and a detection limit of 0.43 μM in the detection range from 0.5 to 50 μM. The practical applicability of the sensor was also studied in tomato samples, promising satisfactory results toward 4-NP detection in other real samples.
In this work, we systematically investigated and compared the electrochemical sensing performances of three electrodes modified with various bio-AgNPs toward 4-NP detection in tomato samples.
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•Alternative biofuel from the algal, plant, and cyanobacterial biomass.•Biohydrogen production is less harmful and high yield.•Different types of enzymes involved in the mechanism of ...biohydrogen production.•Genetic modification of algae could improve the yield of biohydrogen.
In comparison to other methods of producing hydrogen, the production of biohydrogen is significantly less harmful to the surrounding ecosystem when it was produced from the biological origin such as microalgae. It could take the place of conventional fossil fuels while avoiding the emission of greenhouse gases. The substrates such as food, agricultural waste, and industrial waste can be readily utilized after the necessary pretreatment, led to an increase in the yield of hydrogen. Improving the production of biofuels at each stage can have a significant impact on the final results, making this method a potentially useful instrument. As a consequence of this, numerous approaches to pretreat the algal biomass, numerous types of enzymes and catalyst that play a crucial role for hydrogen production, the variables that influence the production of hydrogen, and the potential applications of genetic engineering have all been comprehensively covered in this study.
Tetrahydrofuran (THF) is well-known as a clathrate former as well as a promoter for gas hydrate formation. This work examines interactions between water and tetrahydrofuran via the effect on water’s ...vibrational spectrum. Due to water’s large oscillator strength in the hydrogen-bonded region, interactions are diagnosed by isolating small clusters in a transparent medium (carbon tetrachloride in this study). A weak THF/water hydrogen bond is reflected by a 3450 cm–1 OH-donor vibration (blue shifted from the water/water hydrogen bond) and a 3685 cm–1 nonbonded OH stretch (blue shifted 22 cm–1 from the decoupled OH stretch in this medium). Increasing the THF concentration results in another 20 cm–1 blue shift of the OH-donor stretch. Additional THF does not complex with free water but rather joins with existing THF/water structures to form a cluster enriched in THF. These results complement previous work examining THF vibrations in clathrate hydrates. Together, they generate a picture in which water mediates between THF pairs mediation that affects vibrational frequencies of both species. In addition to a frequency shift, water’s hydrogen-bonded resonance gains oscillator strength due to its mediating configuration.
Summary
This article provides a comprehensive study on quantitative properties of linear mixed fractional‐order systems with multiple time‐varying delays. The delays can be bounded or unbounded. We ...first obtain a result on existence and uniqueness of solutions to these systems. Then, we prove a necessary and sufficient condition for their positivity. Finally, we provide a necessary and sufficient criterion to characterize asymptotic stability of positive linear mixed fractional‐order systems with multiple time‐varying delays.
The use of zinc and its alloys in rechargeable aqueous batteries faces a major problem: corrosion. This must be overcome to ensure the delivery of the sustainable hybrid rechargeable aqueous battery ...system. In this review, the mechanism of zinc corrosion in acidic aqueous electrolytes has been discussed, followed by a summary of corrosion studying methods. The use of polymer-containing materials to protect zinc from corrosion and their possible applications in batteries are also discussed.
The chemistry, methods, and results of corrosion studies on zinc coating using polymer-containing materials may be exploited in the development of the next generations of hybrid rechargeable aqueous batteries.
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•The present review aims to highlight the importance of biomass.•This review focuses on energy applications of biomass and waste-derived materials.•Waste-derived silica and activated ...carbon play an important role in energy application.
The present review article aims to highlight the importance and availability of biomass and focuses on energy applications such as fuel cells, supercapacitors, batteries, and solar cells from biomass-based materials like silica, activated carbon and ammonia because these materials play a major role in energy application. We specifically discuss the yield, purity, and availability of activated carbon and silica from waste biomass, as well as new developments in this field of biomass and waste-based materials manufacturing processes. This review shows that biomass and waste-based materials have great potential for energy applications. Among them, silica and activated carbon are mostly studying materials. However, ammonia production from biomass is very limited currently. It addresses and encourages additional research to support actual uses of biomass and waste-based materials, especially biomass-derived ammonia in energy storage and conversion domains. Here, we discuss the most recent advancements in biomass and waste-derived materials. In order to gain a better understanding ofthe processes underlying their improved performance, numerous new achievements have been noted. The best biomass and waste-derived materials for futuristic energy devices are then highlighted.
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