The effects of PVP surfactant in the direct and indirect hydrothermal synthesis processes of ceria nanostructures

CeO₂ nanostructures with completely different morphologies were successfully prepared using the same cerium source and mineralizer through the direct and indirect hydrothermal methods with different introducing strategies of PVP surfactant. The CeO₂ nanostructures tend to form the morphologies of nano-flowers and nano-cubes through the indirect and direct hydrothermal methods, respectively. X-ray diffraction (XRD) analyses revealed that both as-prepared nanostructures are composed of CeO₂ with a standard fluorite structure. The different synthesis mechanisms and corresponding chemical evolutions of the as-prepared CeO₂ nanostructures are discussed based on the different introducing strategies of PVP surfactant in the direct and indirect hydrothermal processes. Investigation of the UV-shielding ability of both CeO₂ nanostructures suggested that the UV absorbance of the nano-flowers is much higher than that of the nano-cubes.     

Logistics cost analysis of rice straw pellets for feasible production capacity and spatial scale in heat utilization systems: A case study in Nanporo town,Hokkaido, Japan

Rice straw is a promising renewable energy source because it is abundantly available in Asia. This study conducted a case study of logistics cost analysis for rice straw pellets by considering all stages in the supply chain to define the main factors affecting the selling price of rice straw pellets: collection (job-commission or employment of part-time workers), transportation, storage (vinyl greenhouses or storage buildings with larger capacity), pelletizing, and delivery to users with biomass boilers. The selling price was found to be strongly dependent on the production capacity because the investment cost for the pellet production facility had a significant effect of economies of scale. A production capacity of larger than 1500 t y⁻¹ is required for rice straw pellets to compete with wood pellets and fossil fuels in the studied Japanese context if the subsidy rate for the investment is 50%, part-time workers conduct the collection, and rice straw is stored in the storage buildings. Our sensitivity analysis also showed an economically feasible spatial scale: for example, rice straw should be collected within a 20 km radius and the users should be within a 38 km radius when the production capacity is 1500 t y⁻¹. In addition, other critical factors related to the collection of rice straw from the paddy fields and transportation of rice straw rolls to storage were identified as planning factors to further reduce the total logistics cost of rice straw pellets.     

1D ZnFe2O4 nanorods coupled with plasmonic Ag,Ag2S nanoparticles and Co-Pi cocatalysts for efficient photoelectrochemical water splitting

Improving the absorption of visible light, accelerating the separation of carries and reducing the recombination of electron-hole pairs are critical to enhance photoelectrochemical (PEC) performance of ZnFe₂O₄. Herein, the ZnFe₂O₄/Ag/Ag₂S films are firstly prepared with a photocurrent density of 0.91 mA/cm² at 1.23 V vs. RHE, which is 9.10 times higher than that of pristine ZnFe₂O₄ (0.10 mA/cm² at 1.23 V vs. RHE). On the basis, Co-Pi cocatalyst is deposited on ZnFe₂O₄/Ag/Ag₂S to further optimize PEC performance of ZnFe₂O₄, the photocurrent density of ZnFe₂O₄/Ag/Ag₂S/Co-Pi is 1.18 mA/cm² at 1.23 V vs. RHE. The improved PEC performance of ZnFe₂O₄/Ag/Ag₂S/Co-Pi films could be attributed to: (i) fast transmission of electron-hole pairs owing to 1D ZnFe₂O₄ NRs; (ii) surface plasmon resonance (SPR) effect of Ag nanoparticles; (ⅲ) visible light absorption is improved by sensitization of Ag₂S nanoparticles; (ⅳ) Co-Pi cocatalyst decreases the recombination of electron-hole pairs by capturing holes. This work provides new insights for metal plasmas, sensitizers and cocatalysts synergistically modify photoanodes for efficient PEC water splitting.     

Highly efficient metal-free phosphorus-doped platelet ordered mesoporous carbon for electrocatalytic oxygen reduction

Platinum-free electrocatalysts especially, various heteroatom-doped carbon nanostructures have attracted particular attraction as plausible solution for commercializing fuel cell technology. In this direction, novel phosphorus-doped platelet ordered mesoporous carbon (P-pOMC) is developed for the first time as metal-free electrocatalyst for alkaline oxygen reduction reaction. The P-pOMC is synthesized by nanocasting method using platelet ordered mesoporous silica as template. Various characterizations reveal that the P-pOMC materials have covalently bound P atoms with carbon framework for facilitation of oxygen reduction reaction (ORR) and also have very high surface area with uniform distribution of short mesoporous channels for unhindered mass transfer. Combination of P doping and excellent surface properties empowers the newly-developed P-pOMC catalyst to show high ORR activity nearly equal to that of state of the art Pt catalyst along with superior long-term stability and excellent methanol tolerance.     

Integration of nisin into nanoparticles for application in foods

Nisin and other similar food preservatives of natural origins have seen a substantial upsurge in global interest in recent years. The use of nanotechnology to regulate and manipulate nisin for enhanced capacities in the food and nutrition sector is expanding dramatically. Nanotechnology has significant food science applications in nanoparticle delivery systems, packaging, food security, and safety. However, there have been considerable issues regarding the use of nisin in the food sector, including its uncontrolled interactions with various food components, its degradation and electrostatic repulsion. These issues potentially limit its use. Alternate strategies, including a variety of nanoparticle systems such as nanoemulsions, polymeric nanoparticles, nanofibers, and combinations of nisin with other technologies, are employed to enhance the utility of nisin in the food industry. This review highlights the recent developments and new perspectives related to the uses of nisin in the food industry.Industrial relevanceThis review highlights the current status of nanotechnology in the food industry. The issues concerning use of nisin by the food industry are addressed. Nisin shows enhanced efficacy in combination with other current technologies for improved food safety.     

N,N′-Dibromo-N,N′-1,2-ethanediylbis(benzene sulfonamide) as a novel N-bromo reagent catalyzed tetrahydropyranylation/depyranylation of alcohols and phenols under mild conditions

Preparation and catalytic application of N,N′-dibromo-N,N′-1,2-dethanediylbis(benzene sulfonamide) for tetrahydropyranylation of various types of alcohols and phenols in dichloromethane and depyranylation of these compounds in methanol at room temperature is described.     

氮化物陶瓷粉体的制备技术及发展趋势

氮化物陶瓷具有优异的耐高温、抗腐蚀、耐磨损性能,是一类应用广泛的结构功能材料。采用烧结方式制备结构与性能满足要求的氮化物陶瓷材料,有必要首先合成符合一定纯度和烧结活性的氮化合物粉体。本文综述了传统产业化氮化物陶瓷粉体的制备技术,以及新型合成技术的研究进展;对现有技术中存在的问题做了归纳总结,并依据国家政策层面的需求和支持提出该领域的发展趋势。     

Synthesis and investigation of the properties of poly(methyl-β-cyanoethylsilylene)-methylphenylsilylene

Dichlorosilane monomer methyl-β-cyanoethyldichlorosilane, was prepared from acrylonitrile and methyl dichlorosilane in the catalytic system of N,N,N′,N′-tetramethylethylen-diamin (TMEDA)/Cu₂O by hydrosilylation reaction. Consequently, a copolysilane poly(methyl-β-cyanoethylsilylene)-methylphenylsilylene was synthesized by Wurtz-type reductive coupling reaction of methyl-β-cyanoethyldichlorosilane and methylphenyldichlorosilane using sodium as catalyst in toluene. Furthermore, UV absorption, fluorescent and thermal properties of the copolysilane were investigated. Results reveal that the copolysilane bearing β-cyanoethyl side group possesses good thermal oxidative stability and strong fluorescence emitting at 412 nm.     

Effect of additives on the WGS activity of combustion synthesized CuO/CeO2 catalysts

This paper presents a study on the role of additives (samaria, lanthana, zirconia, and zinc oxide) to ceria as a support of copper catalysts for low-temperature WGSR. A single-step urea-combustion procedure was used for preparation of highly active catalysts. The results revealed the beneficial role of Sm₂O₃ and ZnO doping in increasing BET surface area and total pore volume of the catalysts and decreasing the degree of crystallinity of ceria. TPR profiles evidenced enhanced reducibility of modified catalysts. The WGS activity of these catalysts correlates well with BET, XRD, and TPR data. By comparing the catalysts with a commercial CuO–ZnO–Al₂O₃ sample we point out the feasibility of using CuO/doped-ceria catalysts for low-temperature WGSR.     

Performance evaluation of molybdenum dichalcogenide (MoX2; X= S,Se, Te) nanostructures for hydrogen evolution reaction

Hydrogen evolution reaction (HER) using transition metal dichalcogenides (TMDs) have gained interest owing to their low-cost, abundancy and predominant conductivity. However, forthright comparisons of transition metal chalcogenides for HER are scarcely conducted. In this work, we report the synthesis of series of molybdenum chalcogenide nanostructures MoX₂ (X = S, Se, Te) via a facile hydrothermal method. Used as an electrocatalyst for HER, MoS₂ nanograins, MoSe₂ nanoflowers and MoTe₂ nanotubes could afford the benchmark current densities of 10 mA cm⁻² at the overpotentials of −173 mV, −208 mV and −283 mV with the measured Tafel slope values of 109.81 mV dec⁻¹, 65.92 mV dec⁻¹ and 102.06 mV dec⁻¹, respectively. Besides other factors influencing HER, the role of electronic conductivity in HER of these molybdenum dichalcogenides are elucidated. In addition, the presented molybdenum dichalcogenides in this work are also complimented with robustness as determined from high-current density stability measurements.