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[en] Highlights: • Soluble n-butyl substituted copper phthalocyanine. • Mixture with spiro-OMeTAD and employment in perovskite solar cells. • Impressive improvement of perovskite solar cell efficiency. • n-Butyl derivative gives better results than tert-butyl derivative - Abstract: Perovskite solar cells have been constructed under ambient conditions by using 2,2',7,7'-Tetrakis-(N,N-di-4-methoxyphenylamino)-9,9'-spirobifluorene (spiro-OMeTAD) mixed with a small quantity of soluble tetra-n-butyl substituted copper phthalocyanine as hole transporting material. The introduction of the phthalocyanine derivative resulted in an impressive increase of cell efficiency, which changed from 10.4% in the absence to 15.4% in the presence of phthalocyanine. This effect is related to the creation of deep traps in the hole transporting phase which block back-travelling electrons as well as to the improvement of the structural quality of the spiro-OMeTAD film in the presence of phthalocyanine. Both functionalities decrease shunt paths within the hole transporting phase resulting in increasing the fill factor and the open-circuit voltage of the cell.
[en] The application of electro-technologies to existing biological treatment methods in the United Arab Emirates (UAE) requires further understanding of how microorganisms respond to said electro-technologies. This is necessary in order to optimize and enhance the treated effluent water's quality. Therefore, the primary objective of this research study was to evaluate the microbial communities present in a bio-electrochemical reactor under different operating conditions where variables such as current density and exposure time to electric field were modified in order to achieve system process stability. This study was divided into three Phases. In Phase 1, a laboratory scale study was conducted at different current densities ranging between 5 and 20 A m−2 continuously supplied with no addition of substrate. In Phase 2, a laboratory scale study was conducted at continuous supply of electric field at different current densities ranging between 5 and 20 A m−2 (Stage 1), and at intermittent supply of electric field at constant current density of 15 A m−2 (Stage 2). In each Phase, biokinetics (bacterial counts, growth rates and doubling times), and substrate utilization rate (organic removal) were assessed. Overall, results showed that continuous and intermittent supply of electric field significantly increased observed bacterial counts, growth rates, and soluble chemical oxygen demand (sCOD) removal at lower current densities. High resolution melting analysis (HRM) from Phase 3 indicated that intermittent supply of electric field caused a shift in the microbial population structure in a wastewater bioreactor, while no shift in microbial community population structure was observed in reactors supplied with constant current densities. Taken together, the results presented here indicate that introducing low intermittent or constant electrical current densities to existing biological treatment methods in the UAE has the potential to lead to more efficient and improved reactors for the treatment of wastewater.
[en] Multipodal molecular platforms were designed recently to establish a well-defined contact between molecular electronic components and metallic electrodes to manufacture working devices based on molecular electronics. In this work, we use electrochemical techniques, scanning tunneling microscopy break junction technique and theoretical approaches combining density functional theory (DFT) and non-equilibrium Green's function (NEGF) formalism to investigate the geometrical arrangement and single molecule charge transport in self-assembled monolayers (SAMs) of molecular towers anchored by tetraphenylmethane tripod on Au (111) surface. The effect of the molecular length as well as the role of the position of anchoring groups was addressed. Electrochemical double-layer capacitance measurements and reductive desorption studies combined with theoretical modeling clearly demonstrated that the molecular towers form densely packed SAMs, in which the individual molecules are attached to the Au (111) surface by the tripodal base and the principal molecular axis is directed away from the electrode surface, providing thus desired orientation. Temperature resolved single molecule conductance measurements combined with DFT/NEGF calculations showed that the electric charge is transported by tunneling via highly conductive molecular junctions formed by the tripodal base. Our combined experimental and theoretical work demonstrates that tetraphenylmethane tripods are suitable platforms to bear functional groups serving as molecular electronic components.
[en] the electrochemical performance of LiFe0.75Mn0.25PO4 material is further enhanced via synergistic strategies including crystal orientation growth, microspherical self-assembly and graphene encapsulation. The crystal orientation growth of LiFe0.75Mn0.25PO4 with plate-like morphology not only reduces the Li-ion transport length, but also enlarges the (010) surface, and leads to the improvement of Li-ion diffusion. The self-assembled spherical hierarchical superstructures can effectively prevent the plane-plane stacks of LiFe0.75Mn0.25PO4 nanoplates during spontaneously aggregating, providing more (010) surface for Li+ insertion/extraction. The graphene encapsulation can build a 3D conductive network as well as stabilize the microspherical aggregations, resulting in superior electronic conductivity and stability. As a consequence of the synergistic effects, the as-obtained LiFe0.75Mn0.25PO4 sample exhibits excellent rate capability (141.1 mA h g−1 at 5 C, 126.5 mA h g−1 at 10 C, 107.7 mA h g−1 at 20 C) and outstanding cyclability (25 °C, 94.6% capacity retention after 500 cycles at 1 C). The synergistic strategy involving crystal orientation growth, microspherical self-assembly and graphene encapsulation provides a fascinating candidate to obtain superior olivine-type cathode materials with excellent rate capability and cycling stability, and holds the potential to be extended to the controlled preparation of other electrode materials.
[en] Graphical abstract: Rosalike CuSe hierarchical nanostructures modified TiO2 NTs were firstly synthesized by a facile photo-assisted chemical bath deposition method. The p-type CuSe with the average diameter of 2–4 μm were well well-proportionedly grown on the top surface of n-type TiO2 NTs, forming the p–n heterojunction. And the morphology of an individual CuSe looks like a beautiful flower of rosa in nature. The rosalike hierarchical nanostructures with high surface area will facilitate the adsorption and photocatalysis of reactants. Thus, the resulting hybrid materials exhibit improved photocatalytic activities in degrading anthracene-9-carboxylic acid compared with the unmodified TiO2 nanotubes under simulated solar light. Highlights: ► CuSe hierarchical nanostructures were grown on TiO2 nanotubes using photo-assisted chemical bath deposition. ► The fabrication technique of CuSe operated at room temperature and room pressure. ► The hierarchical nanostructures with high surface area facilitated the adsorption and photocatalysis of reactants. ► The hybrid materials exhibited improved photocatalytic activities compared with the unmodified TiO2 nanotubes. ► A possible mechanism was proposed to explain the formation of rosalike architecture CuSe at low temperature. - Abstract: Highly crystalline CuSe hierarchical nanostructures made of nanosheets have been successfully synthesized on the surface of TiO2 nanotube arrays (NTs) pre-loaded with Cu2O nanowires using a photo-assisted chemical bath deposition. The pre-synthesized Cu2O nanowires served as copper precursor and nucleation centers for the crystal growth, resulting in the rapid formation of CuSe crystals at low temperature. This novel material held the advantages of both p–n junction and hierarchical nanostructures which provided high specific surface areas, thus facilitating the transfer of the electrons and inhibiting the recombination of the photogenerated hole-electron pairs, which were demonstrated by photoelectrochemistry measurements. Meanwhile, UV–vis diffuse reflectance spectra (DRS) showed the modified TiO2 significantly enhanced the absorption in the visible light region. X-ray diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM) were employed to demonstrate that the resulting CuSe was single crystalline. A possible mechanism was proposed to explain the formation of rosalike architecture CuSe at low temperature. In addition, this novel material exhibited remarkable photocatalytic performance on the degradation of anthracene-9-carboxylic acid (ACA).
[en] Highlights: • The impedance of the ohmic loss in PEM fuel cells is analytically determined. • The equivalent circuit and impedance characteristics are specified. • The predicted impedances are verified based on measured impedances in literature. - Abstract: The impedance characteristics of the ohmic loss in proton exchange membrane fuel cells are studied analytically, presenting a process model. The governing equations describing the ohmic loss and the water transport in the membrane and the cathode gas diffusion layer are analytically solved and the impedance is determined. Then, an equivalent circuit is presented as a function of the fuel cell properties and operating conditions. Various characteristics and specifications of the determined equivalent circuit are studied. The results obtained from the equivalent circuit are in agreement with the measured fuel cell impedances reported in the literature. It is shown that the membrane ohmic loss is the dominant part of the high frequency resistance, and the membrane and cathode gas diffusion layer water transport impacts the low frequency arc and the inductive loop in the Nyquist plot, respectively. Also, the membrane diffusion coefficient can be extracted from the time constant of the low frequency semi-circle in the Nyquist plot
[en] Highlights: • Calendar aging under different storage conditions for three different battery technologies studied. • Two scenarios of aging under power cycling at two different temperatures investigated for one battery technology. • Relaxation profile of battery voltage just after full charge is highly correlated to aging. • Linear dependence between just after charge open circuit voltage and remaining capacity demonstrated. • No computational method and direct prediction of battery state of health or remaining capacity. - Abstract: The performance of lithium batteries degrades over time. The degradation rate strongly depends on stress conditions during use and even at rest. Thus, accurate and rapid diagnosis of battery state of health (SOH) is necessary for electric vehicle manufacturers to manage their vehicle fleets and warranties. This paper demonstrates a simple method for assessing SOH related to battery energy capability (SOHE). The presented method is based on the monitoring of Urelax over aging. Urelax is the open-circuit voltage of the battery measured after full charging and 30 min of rest. A linear dependence between Urelax and remaining capacity is noted. This correlation is demonstrated for three different commercial battery technologies (different chemistries) aged under different calendar and power cycling aging conditions. It was determined that the difference between two Urelax voltages measured at two different aging states is proportional to SOHE decay. The mean error of the linear model is less than 2% for certain cases. This method could also be a highly useful and rapid tool for a complete battery pack diagnosis.
[en] Equivalent circuit model (ECM)-based state-of-charge (SOC) estimation has been considered as one of the most important aspects in battery management system (BMS). However, in case of a lithium iron phosphate (LiFePO4) cell, because of the flatness and hysteresis effect of the open-circuit voltage (OCV) curve, there are inevitable drawbacks directly related to both erroneous SOC information and the slow SOC convergence speed caused by incorrect OCV characteristics. Therefore, this approach gives insight to the design and implementation of the ECM-based SOC estimator that is suitable for an actual LiFePO4 cell. Two approaches for settlement in current OCV issues are as follows. Firstly, through linearization between coordinated charging and discharging OCVs, an OCV hysteresis model can be easily implemented. This model incorporating OCV measurement data is adequately applied to the model-based SOC estimator using the extended Kalman filter (EKF). Secondly, a well-adjusted measurement error covariance controlled in the EKF is used to alleviate an undesired SOC fluctuation that surely results in low BMS performance. This measurement error covariance additionally enables us to provide the fast SOC convergence speed against an inaccurate initial SOC value. This approach has been sufficiently validated by extensive experimental results conducted on LiFePO4 cells that had a rated capacity of 14 Ah by EIG. Consequently, our validation showed the clearness of the proposed work for a reliable SOC estimator of a LiFePO4 cell.
[en] Highlights: • Cu-Ni-W/SiC nano composite coatings were electrodeposited on steel. • Effects of the concentration nano SiC particles, stirring rate and current density on incorporation of nano SiC particles were investigated. • Effects of incorporation SiC particles in the coatings on microstructure and mechanical properties of the nano composite coatings were investigated. • The incorporation of nano SiC particles in the coatings leads to increasing wear resistance and microhardness of the coatings. - Abstract: In this work Cu-Ni-W/SiC nanocomposite coatings were prepared by electrodeposition method and the effects of incorporation of silicon carbide (SiC) nanoparticles on microstructure and wear resistance of Cu-Ni-W coatings were investigated. In this regard, the effects of various parameters such as concentration of SiC nanoparticles, stirring rate and current density on incorporation of SiC nanoparticles were examined by scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX) to reach the optimum composition for the bath. In addition, the effects of SiC nanoparticles on the wear resistance of the coatings was examined by pin on disk wear technique. It was found that in comparison with other coatings, the coating electrodeposited from the bath containing 15 g/L SiC nanoparticles at a current density of 20 mA.cm"−"2 and stirring rate of 400 rpm has the highest microhardness and wear resistance
[en] Highlights: • Electrochemistry on thiadiazine-based compounds. • Energy level approximation. • Low-bandgap copolymer electron accepting building blocks. • Design rules for “push–pull” copolymerization approaches using thiadiazines. -- Abstract: A series of synthesized small organic molecules based on the 4H-1,2,6-thiadiazine moiety are studied using electrochemistry, to probe their potential as comonomer building blocks for solar-absorbing polymers for organic solar cells. This is the first instance of an electrochemical report for this family of heterocycles. Structure–physical property relationships are identified that can guide future synthetic efforts. Parameters that can influence the properties of the final copolymer such as the choice of electron donor comonomer and the energy level of the fullerene adduct acceptor are factored-in and discussed and the thiadiazines that can meet the requirements are singled-out