Morphology selective electrodeposition of Cu2O microcrystals on ZnO nanotube arrays as efficient visible-light-driven photo-electrode

ZnO nanotube arrays were synthesized by the electrodeposition method and Cu₂O microcrystals with two kinds of morphologies were deposited on ZnO nanotube arrays successfully. At the deposition potential of −0.5 or −0.7 V, the cubic or spherical Cu₂O microcrystals were selectively deposited on ZnO nanotube arrays. By adjusting the deposition time, Cu₂O microcrystals with different sizes were obtained. The optical properties and photo-electrochemical performance of ZnO/Cu₂O were measured. The results showed that the as-prepared ZnO/Cu₂O heterojunction exhibited improved visible light absorption and enhanced photocurrent due to the excellent ability of Cu₂O microcrystals for harvesting visible light, and the effective separation and transfer of photo-generated electrons and holes owing to p-n junction between ZnO and Cu₂O. The experimental results demonstrate that the photo-electrochemical performance of ZnO/Cu₂O heterojunction nanotube arrays can be manipulated by controlling the morphology and the size of Cu₂O microcrystals.     

Switchgrass growth and morphological changes under established pine-grass agroforestry systems in the lower coastal plain of North Carolina,United States

Switchgrass (Panicum virgatum L.) intercropped with Loblolly pine (Pinus taeda L.) has been proposed as a potential biomass feedstock for biofuel production in the southeastern United States. This study investigated effects of treatments (intercropping vs. grass only) on biomass increment processes and morphological properties of switchgrass at two experimental plots (Lenoir1) located in the coastal plain of North Carolina. We also evaluated effects of trimming lower tree branches of pine trees on switchgrass growth at another watershed-scale site (Carteret7) in the same region. Results showed that biomass yield of intercropped switchgrass was reduced by adjacent trees and negatively affected by relative position of grass to trees at the 6th year after planting at Lenoir1. Relative grass-to-tree position was also found to be a significant (p < 0.001) factor affecting grass growth at Carteret7 site with tree age of 5 years old, which is irrespective to the trimming practice. Trimming lower tree branches did not significantly (p = 0.57) improve biomass yield of switchgrass at Carteret7. We also observed intercropped switchgrass typically had higher specific leaf area and grew taller compared to grass-only plots. Stem-to-leaf ratios of switchgrass were significantly (p = 0.02) affected by trees at Lenoir1, but not by trimming lower branches in Carteret7 and relative position of grass to trees at both study sites. Findings from this study are important for evaluating the viability of producing biofuel feedstocks using this proposed intercropping system in the southeastern United States.     

Morphological engineering of carbon-based materials: in the quest of efficient catalysts for overall water splitting

This work attempts to optimize the catalytic activity of the carbon-based materials by engineering their morphological structure. Several flake-like quantum dots with different shapes such as triangulene, elliptical, rhomboid, and square, as well as hydrocarbons having sunflower, kekulene, and snow-like structures, are considered and their electrocatalytic activities toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are theoretically evaluated. The activity analysis indicates that the OER overpotentials for the examined carbon materials vary in the range between 0.56 and 1.22 V. Benefiting from the improved electronic properties due to the proper morphology, remarkable catalytic activity was achieved for the snow-like morphology affording overpotentials of 0.56 V for OER and ?0.05 V for HER. In addition to snow-like, other morphologies such as triangulene and square can effectively promote acidic hydrogen evolution via Volmer-Heyrovsky mechanism. On contrary, the high values of free energies for H₂O dissociation step reveal that, under the alkaline condition, the examined carbon materials cannot be considered as efficient HER catalysts.     

Improving the fill factor of N2200-based all polymer solar cells by introducing EPPDI as a solid additive

A cheap and commercially available small molecule (namely EPPDI) is introduced to the active layer of N2200-based all polymer solar cells as a solid additive. EPPDI at the optimal ratio can improve the D-A nano-scale morphology and reduce trap density of the active layer by filling morphological spaces. As a result, the photovoltaic performance of the resulting devices based on PF2:N2200 are increased from 6.28% to 7.03% with significantly enhanced fill factor. This work demonstrates a facile approach for improving the performance of all polymer solar cells.     

Comparison of steam-alkali-chemical and microwave-alkali pretreatment for enhancing the enzymatic saccharification of oil palm trunk

This paper demonstrates two different pretreatment protocols for oil palm trunks (OPT); steam-alkali-chemical (SAC) and microwave-alkali (Mw-A) method. The composition, morphology, structure and crystallinity of OPT before and after pretreatment were analyzed. The effectiveness of the pretreated methods was investigated by performing enzymatic saccharification on the OPT. The physiochemical factors namely: enzyme ratio (cellulase to β-glucosidase), pH, temperature and substrate loading (w/v) on enzymatic saccharification were also investigated. The pre-determined optimal conditions were then used for further enzymatic hydrolysis of raw and pretreated OPT substrates. The results revealed a huge degree of reduction in lignin, up to 89% for SAC treated OPT and at least 15% for Mw-A treated OPT sample as compared to untreated ones. High glucose accumulation (79.4%) was obtained after 72 h saccharification for both pretreated OPT samples.     

Effects of preparation conditions on the morphology and performance of palladium nanostructures

Three-dimensional palladium nanoflowers (PdNF) composed of ultrathin Pd nanosheets had been synthesized by a solvothermal approach in our previous work. Here, the effects of preparation conditions on the morphology and electrochemical performance of palladium nanostructures were investigated. The explored conditions are as follows: the ratio of reducing agent to capping agent, the concentration of PdCl₂ precursor, the amount of HCl (used for PdCl₂ dissolution), the reaction temperature and time. Only when these conditions are strictly controlled, the obtained Pd material displays a uniformly nanoflower-like morphology, otherwise the Pd samples with nanoparticles or incomplete flowers can only be obtained. Then, the relationship between the morphology of Pd and its electrocatalytic activity was further studied. The results indicate that the Pd with perfect nanoflowers morphology possesses superior activity for formic acid electro-oxidation, while the Pd with incomplete flowers and ordinary (or irregular) particle morphology shows moderate and inferior activity. Therefore, the morphology-dependent electrocatalytic activity has been demonstrated in this work.     

Role of morphology in electrochemical hydrogen storage using binary DyFeO3-ZnO nanocomposites as electrode materials

Hydrogen storage technology is one of the most challenging issues due to the increasing demand for fossil fuel replacement and the reduction of greenhouse gas emissions. In the current paper, the main aim is one-step and eco-friendly preparation of DyFeO₃-ZnO nanocomposites using Barberry fruit extract as natural precursor (with the role of both fuel and capping agent) to compare with various conventional carboxylic acids. To further examine, the effect of different parameters like calcination temperature and the type of the chelating agent was scrutinized to acquire optimum shape, structure, morphology and size of the obtained products. This is the first effort on the investigation of the hydrogen storage capacity of DyFeO₃-ZnO nanocomposites in terms of role of morphology. The electrochemical hydrogen storage capacity of obtained DyFeO₃-ZnO nanocomposites was studied mediated by chronopotentiometry charge-discharge methods in KOH medium. The synthesis of nanocomposites in the presence of chemical or natural capping agent (carboxylic acids or Barberry fruit extract) led to different morphologies which affects to the electrochemical performance. As a result, the electrode which is provided by plate-like DyFeO₃-ZnO nanocomposites performed 600.11 mAh/g discharge capacity compared with other samples. Based on the obtained results, DyFeO₃-ZnO nanocomposites can be promising compounds to improve the electrochemical performance of hydrogen storage.     

Hydrophilic polyurethane acrylate and its physical property for efficient fabrication of organic photovoltaic cells via stamping transfer

Recently, stamping transfer process using by soft mold or film has been considered by promising technology to solve the drawbacks of spin coating such as deposition of large area and specific region, reducing the material loss, and multi-staking device structures. For the previous researches, polyurethane acrylate (PUA) stamp was essentially treated the 1H, 1H, 2H, 2H-Perfluorooctyltrichlorosilane (FOTS) for self-assembled monolayer (SAM) onto the Si wafer to modify surface energy. Because the FOTS is known as corrosive material, it is necessary to develop the intrinsic property of PUA with environment friendly. In this research, we investigates non-FOTS based PUA stamping transfer and the different surface energy properties that result in various physical phenomena when used for organic photovoltaics. To transfer the material, the energy release rate (G) between the PUA and the coated material should be smaller than the G between the coated material and the substrate. As a result, hydrophilic PUA was used to reduce the interaction between the PUA and the organic bulk heterojunction (BHJ) layer to transfer the BHJ layer from the PUA stamp to a PEDOT:PSS-coated ITO-substrate. 2-Hydroxyethyl methacrylate (HEMA) is included as the reactive diluent to reduce the PUA viscosity, and the contact angle was measured to compare the surface property between the reference PUA and the HEMA-PUA. The stamping-transferred BHJ device exhibits a 95% relative efficiency (2.9%) when compared to that obtained when using a spin-coating process, which is considered as a good alternative to fabricate optoelectronic devices. More importantly, we have found a decrease in the fill factor (64%–58%) and a comparable performance (3.0%–2.9%) derived from the increase in the charge recombination and resistance during the stamping transfer.     

Effect of TiO2 addition on the sintering densification and mechanical properties of MgAl2O4–CaAl4O7–CaAl12O19 composite

Materials designed in the high-alumina region of Al₂O₃–MgO–CaO system have been widely used in many technological fields. However, their further applications are limited by the high sintering temperatures necessary to achieve densification due to the poor sintering ability of calcium hexaluminate (CaAl₁₂O₁₉) and spinel (MgAl₂O₄). Considering this aspect, the present work investigated the effect of TiO₂ addition on the sintering densification and mechanical properties of MgAl₂O₄–CaAl₄O₇–CaAl₁₂O₁₉ composite by solid state reaction sintering. The results showed that the CA₆ grains presented a more equiaxed morphology instead of platelet structure by incorporating Ti⁴⁺ into its structure, which greatly improved the densification after heating at 1600 °C. The flexural strength was greatly enhanced with increasing addition of TiO₂ due to the significant decrease in porosity and improvement in uniformity of grain size as well as the absence of microcracks in the presence of Al₂TiO₅. The increased content of TiO₂ also played an active role in toughening this composite attributed to the increase in resistance to crack initiation and propagation.