Structure-dependent activity and stability of Al2O3 supported Rh catalysts for the steam reforming of n-dodecane

Steam reforming of liquid hydrocarbon fuels is an appealing way for the production of hydrogen. In this work, the Rh/Al₂O₃ catalysts with nanorod (NR), nanofiber (NF) and sponge-shaped (SP) alumina supports were successfully designed for the steam reforming of n-dodecane as a surrogate compound for diesel/jet fuels. The catalysts before and after reaction were well characterized by using ICP, XRD, N₂ adsorption, TEM, HAADF-STEM, H₂-TPR, CO chemisorption, NH₃-TPD, CO₂-TPD, XPS, Al²⁷ NMR and TG. The results confirmed that the dispersion and surface structure of Rh species is quite dependent on the enclosed various morphologies. Rh/Al₂O₃-NR possesses highly dispersed, uniform and accessible Rh particles with the highest percentage of surface electron deficient Rh⁰ active species, which due to the unique properties of Al₂O₃ nanorod including high crystallinity, relatively large alumina particle size, thermal stability, and large pore volume and size. As a consequent, Rh/Al₂O₃-NR catalyst exhibited superior catalytic activity towards steam reforming reactions and hydrogen production rate over other two catalysts. Especially, Rh/Al₂O₃-NR catalyst showed the highest hydrogen production rate of 87,600 mmol g_fuel^?1 g_Rh^?1min^?1 among any Rh-based catalysts and other noble metal-based catalysts to date. After long-term reaction, a significant deactivation occurred on Rh/Al₂O₃–NF and Rh/Al₂O₃-SP catalysts, due to aggregation and sintering of Rh metal particles, coke deposition and poor hydrothermal stability of nanofibrous structure. In contrast, the Rh/Al₂O₃-NR catalyst shows excellent reforming stability with negligible coke formation. No significantly sintering and aggregation of the Rh particles is observed after long-term reaction. Such great catalyst stability can be explained by the role of hydrothermal stable nanorod alumina support, which not only provides a unique environment for the stabilization of uniform and small-size Rh particles but also affords strong surface basic sites.     

Polyaniline encapsulated Ti-MOF/CoS for efficient photocatalytic hydrogen evolution

We report the study of conductive polyaniline (PANI) chain embedded Ti-MOF functionalized with CoS as a cocatalyst for hydrogen evolution reaction (HER) application. The post synthetically modified hybrid photocatalyst PANI/Ti-MOF/CoS greatly influences the redox and e^? ? h⁺ separation process and exhibits an impressive rate of HER (～1322 μmol h^?1g^?1), suppressing the pristine Ti-MOF (～62 μmol h^?1g^?1) with apparent quantum yield (AQY) of ～3.2 and transient current response of ～46.4 μA cm^?2. In this system, Ti-MOF provides the circulation of Ti³⁺ and Ti⁴⁺ to the reaction of photocatalytic H₂ generation, where the additional PANI and CoS amended the performance of H₂ production through electron enrichment and thereby improving the stability and integrity of Ti-MOF. The Electrochemical studies demonstrated increased photocurrent by interweaving Ti-MOF crystal with PANI through cation-π interaction thereby enhancing interface connection and then promoting electron transfers. The charge dynamics revealed the initial charge transfer from photoexcited PANI to encapsulated MOF framework to boost the photocatalytic performance of the system. Further, the electron movement at the Ti-MOF/CoS interface is investigated through work function and electrochemical potential of electrons (Fermi level). DFT results demonstrate the importance of CoS in improving the photocatalytic performance of hybrid Ti-MOF catalyst, which leads to superior catalytic behaviour. These results establish that the encapsulation of catalytic active sites inside MOFs with desirable energy band gaps would be an ideal choice for the production of solar fuels.     

IRS辅助的SWIPT系统中基于能效优先的波束成形设计与优化

以智能反射面(intelligent reflecting surface,IRS)辅助的无线携能通信(simultaneous wireless information and power transfer,SWIPT)系统为背景,研究了该系统中基于能效优先的多天线发送端有源波束成形与IRS无源波束成形联合设计与优化方法。以最大化接收端的最小能效为优化目标,构造在发送端功率、接收端能量阈值、IRS相移等多约束下的非线性优化问题,用交替方向乘子法(alternating direction method of multipliers,ADMM)求解。采用Dinkelbach算法转化目标函数,通过奇异值分解(singular value decomposition,SVD)和半定松弛(semi-definite relaxation,SDR)得到发送端有源波束成形向量。采用SDR得到IRS相移矩阵与反射波束成形向量。结果表明,该系统显著降低了系统能量收集(energy harvesting,EH)接收端的能量阈值。当系统总电路功耗为?15 dBm时,所提方案的用户能效为300 KB/J。当IRS反射阵源数与发送天线数均为最大值时,系统可达最大能效。     

Quantification of Dendritic Spines Remodeling under Physiological Stimuli and in Pathological Conditions

Numerous brain diseases are associated with abnormalities in morphology and density of dendritic spines, small membranous protrusions whose structural geometry correlates with the strength of synaptic connections. Thus, the quantitative analysis of dendritic spines remodeling in microscopic images is one of the key elements towards understanding mechanisms of structural neuronal plasticity and bases of brain pathology. In the following article, we review experimental approaches designed to assess quantitative features of dendritic spines under physiological stimuli and in pathological conditions. We compare various methodological pipelines of biological models, sample preparation, data analysis, image acquisition, sample size, and statistical analysis. The methodology and results of relevant experiments are systematically summarized in a tabular form. In particular, we focus on quantitative data regarding the number of animals, cells, dendritic spines, types of studied parameters, size of observed changes, and their statistical significance.     

Recursive algorithm for modeling non-linear etching rates in reactive plasma jet based optical surface machining of borosilicate crown glass

Application-specific optical glass properties are achieved by utilizing complex material compositions. This can be problematic in reactive plasma-assisted deterministic surface processing since a non-volatile surface layer may form depending on the glass composition, which affects the etch rate and thereby the local etching depth. In this investigation, a model algorithm is proposed to tackle some restrictions in applying fluorine-based plasma jet as etching tool utilized for freeform surface machining of optics made of complex glass composition, like borosilicate crown glass (e.g., N-BK7®). In this regard, firstly an analytical model is proposed for estimating the depth-dependent etch rate function. Subsequently, a recursive simulation algorithm is introduced for convolving the derived depth-dependent etch rate function with the given dwell time matrix to simulate a deterministic freeform generation process. By the proposed simulation algorithm, the impeding influence of the residual layer on the reduction of etching depth is computed prior to a real experiment in order to scale the local dwell time to ensure the targeted local removal. Finally, the simulated freeform shape is compared with the corresponding result of an etching experiment to validate the feasibility of the proposed approach.     

Surface Reconstruction Engineering with Synergistic Effect of Mixed-Salt Passivation Treatment toward Efficient and Stable Perovskite Solar Cells

Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI₂. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.     

Evolution of the electrical resistivity at rest and during oscillatory shearing of co-continuous morphology (PP/PMMA)/MWCNT systems

In this work, a modified parallel-disks configuration on a strain-controlled ARES rheometer (TA Instrument) was used to study the evolution of the electrical resistivity at rest and during oscillatory shearing of a co-continuous immiscible polymer blend morphology based on polypropylene and /polymethyl(methacrylate) (PP/PMMA) in which various amounts (0–3 wt%) of multiwall carbon nanotubes (MWCNT) were added. The co-continuity of both PP and PMMA phases allowed the buildup of a conductive network due to the preferential localization of the conductive MWCNT at the interface between PP and PMMA. Under a stepwise increase of the oscillatory strain amplitude below a critical value (γ_c = 6.3%), a significant decrease in the electrical resistivity was observed for MWCNT concentrations above the percolation threshold (0.3 wt%) due to the conductive paths induced by both thermal (Brownian) motion and oscillatory shearing. However, for deformation amplitudes higher than γ_c, the resistivity increased due to the destruction of the MWCNT paths induced by the large deformation imposed on the PP/PMMA interface. These observations were also confirmed by the evolution of the storage modulus (G′) which remained constant for γ_c < 6.3% (linear viscoelastic regime), while the values decreased above γ_c due to the destruction of the system's morphology.     

Nanoraspberry-like palladium/spongy nickel oxide for electrooxidation of five light fuels

The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage.     

Greatly improved NIR shielding performance of CuS nanocrystals by gallium doping for energy efficient window

In this work, gallium doped copper sulfide (Ga-doped CuS) nanocrystals were prepared using a solvothermal method. The effects of Ga doping on the crystal structures, chemical composition, morphology, optical properties and thermal performance of copper sulfide (CuS) were investigated. The Ga-doped CuS nanocrystals had a hexagonal structure comparable to that of pure CuS. The Cu⁺/Cu²⁺ ratio first decreased and then increased with increasing Ga³⁺ doping. Both CuS and Ga-doped CuS exhibited nanoplate and nanorod morphologies. The visible transmittance of the Ga-doped CuS films was in the range of 61–77.1%. Importantly, the near-infrared (NIR) shielding performance of the films can be tuned by adjusting the concentration of the Ga dopant. The NIR shielding value of the optimal Ga-doped CuS film was 72.4%, which was approximately 1.5 times as high as that of the pure CuS film. This can be ascribed to the enhanced plasmonic NIR absorption that resulted from an increase in the hole concentration after doping with Ga³⁺ ions. In the thermal performance test, the Ga-doped CuS film lowered the interior temperature of the heat box by 9.1 °C. Therefore, the integration of good visible transmittance and high NIR shielding performance make the Ga-doped CuS nanocrystals a promising candidate for energy-efficient window coatings.