One-step sonochemical synthesis of NiMn-LDH for supercapacitors and overall water splitting

Transition metals are attracting numerous interests for their substantial applications in supercapacitors and as non-noble metal electrocatalyst for overall water splitting. Herein, the NiMn layer double hydroxide (NiMn-LDH) is developed using the sonochemical route at different reaction times, which act as a multifunctional electrode for supercapacitors and overall water splitting. The capacitance of layer double hydroxide (LDH) synthesized at 4 h (NiMn-LDH-4 h) of reaction time was found to be 527 F g^?1 at 1 A g^?1, with 91.2% capacitance retention after 5,000 cycles at 2 A g^?1 in 6 M KOH. For hydrogen and oxygen evolution reactions, the NiMn-LDH-4 h electrode exhibits a standard of 10 mA cm^?2 at an overpotential of 120 mV and 296 mV, respectively, in 1 M KOH. Moreover, fabricated NiMn-LDH-4 h||NiMn-LDH-4 h electrolyzer for overall water splitting benchmarks 10 mA cm^?2 at 1.6 V. The superior electrochemical properties of the NiMn-LDH electrodes might be attributed to quick diffusion paths and enhanced redox reaction of NiMn-LDH nanosheets because of the high surface area.

     

Morphology Tailored Synthesis of C-WO<Subscript>3</Subscript> nanostructures and its Photocatalytic Application

Photocatalytic degradation is an ambitious and cost effective technique used for decontamination and sanitization of the waste polluted water of environment. Hydrothermal method is used to synthesis the carbon coupled WO₃ nanoparticles with different concentrations of carbon (0.0, 0.2, 0.5, 1.0 and 2.0%) from precursor Na₂WO₄·2H₂O with glucose and nitric acid. Synthesized nanoparticles were characterized by SEM, EDX, XRD, UV–Vis, and PL to study morphology, and particle size, composition, structural and optical properties, respectively. SEM revealed that morphology of the carbon coupled WO₃ nanoparticles becomes spherical by increasing amount of coupled carbon atoms. The average grain size of the carbon doped nanoparticles is found to be 15–20 nm. Furthermore, size of nanoparticles affect the band gap of synthesized nanoparticles as well. It has also been observed that carbon coupled WO₃ nanoparticles effectively take part in photo degradation due to reduction of electron–hole recombination rate.     

Grid to wheel energy efficiency analysis of battery‐ and fuel cell–powered vehicles

Sustainable energy consumption is an important part of the renewable energy economy as renewable energy generation and storage. Almost one‐third of the global energy consumption can be credited to the transportation of goods and people around the globe. To move towards a renewable energy–based economy, we must adopt to a more sustainable energy consumption pattern worldwide especially in the transportation sector. In this article, a comparison is being made between the energy efficiency of a fuel cell vehicle and a battery electric vehicle. A very simple yet logical approach has been followed to determine the overall energy required by each vehicle. Other factors that hinder the progress of fuel cell vehicle in market are also discussed. Additionally, the prospects of a hydrogen economy are also discussed in detail. The arguments raised in this article are based on physics, economic analyses, and laws of thermodynamics. It clearly shows that an “electric economy” makes far greater sense than a “hydrogen economy.” The main objective of this analysis is to determine the energy efficacy of battery‐powered vehicles as compared to fuel cell–powered vehicles.     

Effect of Ho3+ ions on microwave losses and high-temperature electrical behavior of Li-based magnetic oxides

We investigate here the effect of holmium on Li–Co nano-ferrites to elaborate the surface morphology, dynamic magnetic and electrical transport properties. The transmission electron microscopy (TEM) technique was employed to examine the microstructure and grain size distribution. TEM analysis confirmed the nanocrystalline nature (~50 nm) of the prepared materials. X-ray photoelectron spectroscopy (XPS) experiment results verify the presence of all metal ions with the required valences. Ferromagnetic resonance (FMR) analysis revealed the need for a dense microstructure to cut down the microwave losses. FMR line width was observed to reduce from 2757 -to 1676 Oe except for x = 0.12 by the substitution of Ho ions which correspond to low microwave losses. The dc resistivity results show that high resistivity values are associated with smaller grains of the samples and vice versa. Resistivity values are found to increase from 3.66 × 10⁸ -to 5.31 × 10⁸ Ω-cm by increasing the Ho addition. Seebeck experiment revealed n-type conduction. Together with showing the nature of charge carriers, a decrease in the Seebeck coefficient with increasing Ho ensured the replacement of Fe ions by Ho ions on B-sites.     

Designing an experimental rig for developing a fire severity model using numerical simulation

In this study, an experimental rig representing a deep enclosure was designed to be used to validate a CFD‐based fire model in predicting the outcome. The model then can be used for further study to investigate physical phenomenon within a deep enclosure and to develop an engineering fire severity (heat release rate, HRR, vs time vs position [1]) model. Two empirical models (the VU model [1] and Kawagoe model [2]) were used along with Fire Dynamics Simulator (FDS) in designing the experimental rig. For a specific‐sized enclosure, when the HRR was prescribed to the FDS as input from the VU model, it was accurately reproduced, while the HRR from the Kawagoe was used as the input, the FDS calculated much lower value. The experimental rig of that specific size was then built, and various parameters were measured from the tests with liquid fuel fire within this experimental rig. The measured HRR was prescribed into the FDS, and the FDS could reproduce HRR values well. However, the predicted temperature and radiation flux was not as good, especially when the flames were near the opening. This may be due to the tendency of flames over‐projecting outside the opening in FDS simulations.     

State estimation for short‐time switched linear systems under asynchronous switching

In this note, the state estimation problem for a class of short‐time switched linear systems is investigated. By incorporating the concept of finite‐time stability, an observer is designed to ensure the error dynamics finite‐time stable in the short‐time switching interval under the general asynchronous switching whereas synchronous switching mode is its special case. A numerical example is provided to illustrate the effectiveness of our study in this paper. Copyright © 2013 John Wiley & Sons, Ltd.     

Facile hydrothermal synthesis of 3D flower‐like La‐MoS2 nanostructure for photocatalytic hydrogen energy production

Three‐dimensional (3D) flower‐like MoS₂ nanostructures were prepared via facile and cost‐effective hydrothermal method by varying hydrothermal temperature (180°C, 200°C, and 220°C) and reaction time (6, 12, 24, and 36 hours). The results demonstrated that the sample prepared at 200°C for 24 hours have 3D flower‐like MoS₂ nanostructure (SEM) with hexagonal phase structure (XRD). Moreover, this novel photocatalyst was also modified by lanthanum element (La³⁺) with varying La³⁺ atomic ratio (0.5%, 1%, 2%, 3%, and 4%). Interestingly, the La³⁺ incorporation into MoS₂ has good effect on the specific surface area and optical properties of MoS₂ photocatalyst. Furthermore, the flower‐like 3%LaMoS₂ nanostructure photocatalyst exhibited 5.2‐times higher efficiency for H₂ evolution via water splitting as compared with pure MoS₂ under the same conditions. This superior efficiency of the photocatalyst for H₂ production arises from the positive synergistic effect between MoS₂ and lanthanum in the composite photocatalyst due to higher surface area, enhanced light absorption, and inhibited electron‐holes pair recombination. This study presents an expensive photocatalyst for energy production via water spitting.