Materials for Renewable and Sustainable Energy最新文献

Mechanical milling and a gas-selective polymer were used to protect MgH₂ from oxidation and improve its dehydrogenation properties. MgH₂ and poly(methyl methacrylate) (PMMA) were simultaneously ball-milled for 5 and 20?h, respectively, to prepare an air-resistant nanostructured composite. The properties of the nanostructured composite were studied by XRD, SEM, and FTIR methods. The dehydrogenation performance of all samples was investigated by TGA analysis. The hydrogen desorption performance of ball-milled samples was also evaluated after exposure to air for 4?weeks. Results showed that MgH₂ desorbed about 0.79 wt.% of hydrogen after heating up to 300 ?C and holding for 15?min at this temperature. The ball-milling of MgH₂ and PMMA for 5 and 20?h led to hydrogen desorption of 6.21 and 6.10 wt.% after heating up to 300 ?C and holding for 15?min at this temperature, respectively, which proved the surface protection of MgH₂ from oxidation by PMMA. After 4?weeks of exposing the ball-milled MgH₂–PMMA samples to air, their hydrogen desorption percentage at the same condition changed to 5.80 and 5.72 wt.% for 5 and 20?h milled samples, respectively. A slight reduction in the dehydrogenation percentage of air-exposed samples proved that the air stability of MgH₂ had been significantly enhanced by its confinement with PMMA.

In this work, we report the preparation of TiO₂ nanoparticles with a high surface area, from 120 to 168 m²?g^?1 by the hydrothermal-microemulsion route and hydrothermal temperature effect over particle size, porosity, and photovoltaic parameter. The TiO₂ samples were characterized by Raman, BET, TEM, SEM-FE, I–V curves, and EIS. The increase of hydrothermal temperature correlates with particle and pore size. Although when the synthesis temperature was 250?°C, the surface area presents an unexpected decrease of c.a. 28%. TiO₂ samples were employed as thin-film photo-anodes for dye-sensitized solar cell (DSSC) solar cells. Photovoltaic results showed that the sample prepared at 250?°C presented the more suitable textural properties for the DSSC application. The prepared TiO₂ materials with a particle size of 6.93?±?0.59?nm and anatase crystalline phase favor electron transport and diffusion of electrolyte species, which directly impact in solar cell efficiency.

Nanostructuring approach on TiNiSn-based half-Heusler (HH) thermoelectric materials (TE) has been well established as the most prominent paradigm for achieving high figure of merit (ZT). Herein, we have extended this approach on our previously reported bulk nanocomposite (BNC), containing HH and Full Heusler (FH) with little traces of Ti₆Sn₅ phase in a stoichiometric composition Ti₉Ni₇Sn₈ for the optimization of high thermoelectric performance. A synergistic effect of nanostructuring of Ti₉Ni₇Sn₈ bulk nanocomposite (BNC) on its thermoelectric properties was noticed, revealing an enhanced value of ZT?~?0.83 at 773?K. This enhancement in ZT value is mainly ascribed to significant reduction in thermal conductivity (κ?~?1.0?W/mK at 773?K), through modification in grain as well as phase boundary scattering. The marginal enhancement in Seebeck coefficient observed is attributed to charge carrier filtering effect at the interface of HH/FH phases.

Among novel nanostructured materials, transition metal chalcogenides (i.e., sulfides and selenides) emerged as promising candidates due to their unique electrochemical properties. The following study presents a facile synthesis approach of Bi₂S₃ nanostructures using solvent mixtures of ethanol and water with different volume ratios and ammonium sulfide as a sulfur precursor. The resultant bismuth sulfides were characterized by field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and nitrogen sorption at 77?K. The adjustment of the solvent mixture revealed the possibility of customizing the crystalline structure from amorphous to fully crystalline, as well as the morphology of the Bi₂S₃, which subsequently influenced on their electrochemical properties. Bi₂S₃ synthesized in a solvent mixture of ethanol-to-water volume ratio 1:2 (Bi₂S₃-EW12) exhibited almost fully crystalline structure and nanoplatelet-like morphology, which translated to the best electrochemical performance. Bi₂S₃-EW12 achieved specific capacity of 748?C?g^?1 in an aqueous 6?mol?L^?1 KOH electrolyte and maintained the highest capacity value at a large current density of 20?A?g^?1.

Electrochemical water splitting driven by renewable energy-derived electricity is considered as the most promising pathway for delivering clean and sustainable hydrogen production. The key to achieving an efficient water splitting process is developing highly active electrocatalysts. Two-dimensional (2D) nanomaterials hold great promise in the electrocatalysis field due to their unique physicochemical properties. Some of them are not active enough because of the poor intrinsic activity, low density of active sites or low electrical conductivity. Some are inert for electrocatalytic reactions, but are able to work as the functional substrates for hybrid electrocatalysts. Thus, tremendous strategies have been developed to modulate the physicochemical and electronic properties of 2D nanomaterial-based electrocatalysts, and to make full use of the functionalities of functional 2D nanomaterial substrates to achieve fast catalytic reaction kinetics. In this review, the recent progress on the well-established design strategies for the 2D nanomaterials-based electrocatalysts is highlighted. The perspectives on the?current challenges and future development of 2D electrocatalysts are addressed.

The conversion of model waste plastic mixture into high-value liquid product was studied in the presence of hydrogen and composites of zeolite beta catalysts. For the sake of comparison, the conversion of actual waste plastic mixture and high-density polyethylene was also carried out. The composite zeolite beta catalysts were synthesized using a range of silica-to-alumina ratios, alkali concentrations, and hydrothermal treatment times. SEM, EDX, XRD, N₂-BET, FTIR, and py-FTIR were used for the characterization of the catalysts. The catalytic experiments were conducted in a 500?ml stirred batch reactor at 20?bar initial cold H₂ pressure and the temperature of the reaction was varied between 360 and 400?°C. The two composite catalysts, BC27 and BC48, prepared without alkali pretreatment were found to be the most suitable catalysts. With BC27 and BC48 at 400?°C, 93.0?wt% conversion was obtained with actual plastic mixture and the liquid yield exceeded 68.0?wt%. Experiments with the regenerated catalysts showed their performance comparable to the fresh catalysts.

The production of hydrogen to be used as an alternative renewable energy has been widely explored. Among various methods for producing hydrogen from hydrocarbons, methane decomposition is suitable for generating hydrogen with zero greenhouse gas emissions. The use of high temperatures as a result of strong carbon and hydrogen (C–H) bonds may be reduced by utilizing a suitable catalyst with appropriate catalyst support. Catalysts based on transition metals are preferable in terms of their activeness, handling, and low cost in comparison with noble metals. Further development of catalysts in methane decomposition has been investigated. In this review, the recent progress on methane decomposition in terms of catalytic materials, preparation method, the physicochemical properties of the catalysts and their performance in methane decomposition were presented. The formation of carbon as part of the reaction was also discussed.

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Aerogels are 3-D nanostructures of non-fluid colloidal interconnected porous networks consisting of loosely packed bonded particles that are expanded throughout its volume by gas and exhibit ultra-low density and high specific surface area. Aerogels are normally synthesized through a sol–gel method followed by a special drying technique such as supercritical drying or ambient pressure drying. The fascinating properties of aerogels like high surface area, open porous structure greatly influence the performances of energy conversion and storage devices and encourage the development of sustainable electrochemical devices. Therefore, this review describes on the applications of inorganic, organic and composite aerogel nanostructures to dye-sensitized solar cells, fuel cells, batteries and supercapacitors accompanied by the significant steps involved in the synthesis, mechanism of network formation and various drying techniques.

Direct utilization of hydrocarbon fuels in solid oxide fuel cells (SOFCs) has drawn special attention for high energy conversion efficiency, low cost, and simple devices. However, when fueled with hydrocarbons, SOFCs encountered great difficulty in both performance and stability, which should be attributed to the sluggish hydrocarbon oxidizing reactions, the severe carbon deposition reactions, and the possible sulfur poisoning reactions in the anode. This review summarizes potential anode reactions in hydrocarbon-fueled SOFCs and discusses the possible anode deactivation mechanisms. Further, various strategies to improve the anode performance and stability are reviewed, including substituting alloys or increasing oxide basicity for nickel-based anodes, adopting oxide anodes, and adding catalyst layers. The advantages and challenges of each strategy are discussed. Special attention is paid on properties and models of novel oxide anodes, of which nano-metal catalysts are in-situ exsolved. The publications concerning SOFC anodes, mainly in recent 5?years, are listed and compared in this article.

We examined the electronic property of Sb-doped Na_0.785CoO₂ using density functional calculations based on GGA+U formalism. We demonstrated that Sb dopants were the most stable when replacing Co ions within the complex Na_0.875CoO₂ lattice structure. We also showed that the Sb_Co dopants adopted the?+?5 oxidation state introducing two electrons into the host Na_0.875CoO₂ compound. The newly introduced electrons recombined with holes that were borne on Co⁴⁺ sites that had been created by sodium vacancies. The elimination of Co⁴⁺ species, in turn, rendered Na_0.875(Co_0.9375Sb_0.0625)O₂ non-magnetic and diminished the compound’s thermoelectric effect. Furthermore, the Sb_Co dopants tended to aggregate with the Na vacancies keeping a minimum distance. The conclusions drawn here can be generalised to other highly oxidised dopants in Na_xCoO₂ that replace a Co.