Materials for Renewable and Sustainable Energy最新文献

Biodiesel is an alternative source of renewable energy that can be produced by a transesterification of vegetable oils. Mesoporous molecular sieves, such as SBA-15, due to high surface area and thermal stability are promising precursors for heterogeneous catalysts in the transesterification reaction. In this work, Al-SBA-15 precursor was obtained by direct hydrothermal synthesis, impregnated with different MoO₃ contents (5, 10 and 15 wt%) by the pore saturation method, and evaluated as heterogeneous catalyst in the production of biodiesel from a transesterification of soybean oil with methanol. Al-SBA-15 precursor as well as MoO₃/Al-SBA-15 catalyst were characterized for its structural characteristic by X-ray diffraction, textural characteristic by N₂ adsorption analysis, and thermal stability by thermogravimetric analysis. An experimental planning 2² + 3 CtPt was used to evaluate the influence of MoO₃ content and reaction time on biodiesel yield from soybean oil and methanol. The biodiesel content in the final product was obtained by gas chromatography. An average biodiesel yield of 96% was obtained with the catalyst 10%MoO₃/Al-SBA-15 under the following reaction conditions: 20:1 methanol/soybean oil molar ratio, and 3 wt% of catalyst loading at 150 °C in 3 h. After five consecutive reaction cycles, the biodiesel yield decreased by about 34%. The density and acidity of the biodiesel produced are within the specified values for commercialization according to international standards.

Direct carbon fuel cell (DCFC) is a promising technology with high energy efficiency and abundant fuel. To date, a variety of DCFC configurations have been investigated, with molten hydroxide, molten carbonate or oxides being used as the electrolyte. Recently, there has been particular interest in DCFC with molten carbonate involved. The molten carbonate is either an electrolyte or a catalyst in different cell structures. In this review, we consider carbonate as the clue to discuss the function of carbonate in DCFCs, and start the paper by outlining the developments in terms of molten carbonate (MC)-based DCFC and its electrochemical oxidation processes. Thereafter, the composite electrolyte merging solid carbonate and mixed ionic–electronic conductors (MIEC) are discussed. Hybrid DCFC (HDCFCs?) combining molten carbonate and solid oxide fuel cell (SOFC) are also touched on. The primary function of carbonate (i.e., facilitating ion transfer and expanding the triple-phase boundaries) in these systems, is then discussed in detail. Finally, some issues are identified and a future outlook outlined, including a corrosion attack of cell components, reactions using inorganic salt from fuel ash, and wetting with carbon fuels.

The establishment of perovskite solar cells (PSCs) in terms of their power-conversion efficiency (PCE) over silicon-based solar cells is undeniable. The state-of-art of easy device fabrications of PSCs has enabled them to rapidly gain a place in third-generation photovoltaic technology. Numerous obstacles remain to be addressed in device efficiency and stability. Low performance owing to easily degraded surface and deterioration of perovskite film quality resulting from humidity are issues that often arise. This work explored a new approach to producing high-quality perovskite films prepared under high relative humidity (RH?=?40%–50%). In particular, the ubiquitous 4-tert-butylpyridine (tBp) was introduced into lead iodide (PbI₂) precursor as an additive, and the films were fabricated using a two-step deposition method followed by a delay-deposition technique of methylammonium iodide (MAI). High crystallinity and controlled nucleation of MAI were needed, and this approach revealed the significance of time control to ensure high-quality films with large grain size, high crystallography, wide coverage on substrate, and precise and evenly coupled MAI molecules to PbI₂ films. Compared with the two-step method without time delay, a noticeable improvement in PCE from 3.2 to 8.3% was achieved for the sample prepared with 15?s time delay. This finding was primarily due to the significant enhancement in the open-circuit voltage, short-circuit current, and fill factor of the device. This strategy can effectively improve the morphology and crystallinity of perovskite films, as well as reduce the recombination of photogenerated carriers and increase of current density of devices, thereby achieving improved photovoltaic performance.

In this research, treated metakaolinite (TMK) was introduced into the TiO₂ photoelectrode to fabricated dye-sensitized solar cells (DSSCs). The photovoltaic cells have four main natural components, i.e., a photosensitizer (carotenoid bixin), photoelectrode (TiO₂/kaolinite), electrolyte (glycerine carbonate derivative), and counter-electrode (carbon). Their stability, reusability, and equivalent circuit were studied. The presence of 5% of TMK in anatase TiO₂ paste decreased the TiO₂ band gap from 3.21 to 3.16?eV. The result showed that the presence of 5% of TMK in TiO₂ paste was more favorable to obtain higher energy conversion efficiency. Under a light intensity of 200?W/m², it produced an energy conversion yield of 0.086%. The combination of the electrolyte and the TMK demonstrated a synergistic effect to improve the electrical properties of the DSSC. The energy storage function worked well until the third day of analysis. The DSSC based on TiO₂/TMK photoelectrode exhibited 16 times better stability than pure TiO₂-based photoelectrode. The Faraday charge transfer processes showed that the TiO₂/TMK photoelectrode is not in direct contact with the carbon counter-electrode.

Understanding the mechanism of CO₂ reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO₂ conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO₂ reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO₂ on iron as earlier mechanistic studies are centred on the transformations of the C_2v geometry alone and not the other possible conformations i.e., flip-C_2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO₂ dissociation against the hydrogen-assisted CO₂ transformation through formate and carboxylate into CO and formic acid. Our results show that CO₂ in the C_2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transformation of CO₂ in the Cs and flip-C_2v is challenging kinetically and thermodynamically compared to the C_2v mode. The formic acid formation is favoured over CO via the reverse water gas shift reaction mechanism on Fe (100). Both formic acid formation and CO formation will proceed via the carboxylate intermediate since formate is a stable intermediate whose transformation into formic acid is challenging both kinetically and thermodynamically.

The electrochemical production of green and low-cost ammonia requests the development of high-performance electrocatalysts. In this work, the ampoule method was applied to modulate the surface of the zinc electrode by implanting defects and low-valent active sites. The N-doped ZnS electrocatalyst was thus generated by sulfurization with thiourea and applied for electrocatalytic nitrogen reduction reaction (ENRR). Given the rich sulfur vacancies and abundant Zn-N active sites on the surface, excellent catalytic activity and selectivity were obtained, with an NH₃ yield rate of 2.42?×?10^–10?mol?s^?1?cm^?2 and a Faradaic efficiency of 7.92% at ??0.6?V vs. RHE in 0.1?M KOH solution. Moreover, the as-synthesized zinc electrode exhibits high stability after five recycling tests and a 24?h potentiostatic test. The comparison with Zn foil, non-doping ZnS/Zn and recent metal sulfide electrocatalysts further demonstrated advanced catalytic performance of N@ZnS/Zn for ENRR. By simple synthesis, S vacancies, and N-doping defects, this promising electrocatalyst would represent a good addition to the arena of transition-metal-based catalysts with superior performance in ENRR.

This study has investigated the effect of the incorporation of graphene foam (GF) into the matrix of a ternary transition-metals hydroxide containing nickel, cobalt, and manganese for optimal electrochemical performances as electrodes for supercapacitors applications. An adopted simple, low-cost co-precipitation synthesis method involved the loading a mass of the ternary metal hydroxides (NiCoMn-TH) onto various GF mass loading so as to find ints effect on the electrochemical properties of the hydroxides. Microstructural and chemical composition of the various composite materials were investigated by employing scanning/transmission electron microscopy (SEM/TEM), x-ray diffraction (XRD), Raman spectroscopy, and N₂ physisorption analysis among others. Electrochemical performances of the NiCoMn-TH/200?mg GF composite material evaluated in a three-electrode system using 1?M KOH solution revealed a maximum specific capacity around 178.6 mAh g^?1 compared to 76.2 mAh g^?1 recorded for the NiCoMn-TH pristine material at a specific current of 1 A g^?1. The best mass loading of GF nanomaterial (200?mg GF), was then utilised as a positive electrode material for the design of a novel hybrid device. An assembled hybrid NiCoMn-TH/200?mg GF//CSDAC device utilizing the NiCoMn-TH/200?mg GF and activated carbon derived from the cocoa shell (CSDAC) as a positive and negative electrode, respectively, demonstrated a sustaining specific capacity of 23.4 mAh g^?1 at a specific current of 0.5 A g^?1. The device also yielded sustaining a specific energy and power of about 22.32 Wh kg^?1 and 439.7?W?kg^?1, respectively. After a cycling test of over 15,000 cycles, the device could prove a coulombic efficiency of?~?99.9% and a capacity retention of around 80% within a potential range of 0.0–1.6?V at a specific current of 3?A?g^?1. These results have demonstrated the prodigious electrochemical potentials of the as-synthesized material and its capability to be utilized as an electrode for supercapacitor applications.