查看更多>>摘要：Perovskite solar cells (PSCs) have attracted great attentions due to their excellent photovoltaic performance. Further improvement of device efficiency is limited by the recombination of the charge carriers even a heterojunction-based architecture is employed. Herein, we discovered that a simple surface modification of the perovskite film by incorporating isopropyl alcohol (IPA) post-treatment could convert the top surface to be more n-type, which spontaneously formed an n/n(+) homojunction between the bulk (weak n type (n)) and the surface (more n-type (n(+))) in a single perovskite film. A reconstruction toward a PbI2-rich top surface was induced by the remove of excess formamidinium iodide dissolved in a polar solvent IPA. This reconstructed n/n(+) homojunction lead to the enlarged built-in electric field for efficient charge separation and transport of the photogenerated carriers. The inverted PSCs with the reconstructed n/n+ homojunction contribute to improve efficiency and narrow their efficiency gap with conventional n-i-p type devices. Our result suggests that the homojunction structure is an effective approach to reduce carrier recombination loss and achieve highly efficient PSCs. (C) 2022 Elsevier B.V. All rights reserved.
Dan, Nguyen HuyHau, Kieu XuanYen, Nguyen HaiThanh, Pham Thi...
7页
查看更多>>摘要：Alloy ribbons of Ni50-xCoxMn50-yAly (x = 5, 6, 7, 8 and 9; y = 18 and 19) were fabricated by using melt-spinning method. By varying Co and Al concentrations, the formation of crystalline phases, structural transformations and magnetic phase transitions can be tuned as desired. With high Al and Co concentrations, only a ferromagnetic-paramagnetic (FM-PM) transition of the austenitic phase occurs in the range of 350-450 K. While there is an additional weak ferromagnetic-ferromagnetic (WFM-FM) transition corre-sponding to the martensitic-austenitic (M-A) structural transformation for the ribbons with low Al and Co concentrations. The M-A transformation temperature of the alloy ribbons can be obtained in the range of 150-360 K. An anomalous change in structure and magnetic properties was observed in the ribbon sample with Co and Al concentrations of 8 and 18 at%, respectively. The external magnetic field has a pronounced effect on the M-A transformation and tends to shift this process towards lower temperatures. (C) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：It is of great significance to improve the performance of electrocatalysts by constructing suitable heterogeneous interfaces to adjust the electronic structure of their surfaces. Here, we design and synthesize Co-Fe alloy nanoparticles (NPs) modified nitrogen-doped cubic carbon box (NC) supported MoS2 nanosheets (NC@ MoS2@Co-Fe) as a bi-functional electrocatalytic electrode material, which possesses excellent electrocatalytic oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) performance. The NC@ MoS2@Co-Fe exhibits remarkable bifunctional electrocatalytic activities with an ORR half-wave potential of 0.73 V in 0.1 M KOH electrolyte and an OER overpotential of 400 mV, driving a current density of 10 mA cm-2. The advanced catalytic performance can be attributed to the unique heterojunction structure of the catalyst. The size of the Co-Fe alloy NPs supported on MoS2 can be tuned to avoid the excessive growth of alloy NPs and to expose more catalytic active sites. Meanwhile, the loaded Co-Fe alloy NPs should be covered with a calcined carbon layer derived from the organic ligand to prevent oxidation passivation and particle aggregation. The structure formed by Co-Fe alloy NPs and NC@MoS2 optimizes the electronic structure of the active center and accelerates the electrocatalytic reaction rate, thus synergistically improving the bi-functional electrocatalytic activity of the NC@MoS2@Co-Fe catalyst and can be applied to rechargeable zinc air batteries.
查看更多>>摘要：The effect of the addition of Al2O3 on the viscosity of the iron-compound bearing CaO-SiO2-Al2O3-MgO slags with different SiO2 content (= 30, 40, and 50 wt%) was investigated at high temperatures. The addition of Al2O3 increased the viscosity of iron-compound bearing calcium-aluminosilicate melts. The addition of Al2O3 to the slag at low-SiO2 content (= 30 wt%) increased the fraction of Fe2+ at a fixed iron content because Fe3+ cations prefer to exist as tetrahedral unit, i.e., Fe3+ [IV], in the melt. On the other hand, the addition of Al2O3 to the slag at high-SiO2 content (= 50 wt%) increased the fraction of Fe3+ at a fixed iron content due to the preference of octahedrally coordinated Fe3+ [VI] in the slag. Although the redox equilibrium reaction of iron in the CaO-SiO2-Al2O3-FetO-MgO system was strongly affected by the basicity of the melt, the addition of Al2O3 polymerized silicate networks regardless of the SiO2 content in the slags. The activation energy for the viscous flow of the slags had a linear correlation with the non-bridged oxygen per tetrahedron (NBO/T) in the aluminosilicate network. Therefore, the viscosity of the iron-compound bearing calcium-aluminosilicate melt was determined by the degree of polymerization within the aluminosilicate networks.(c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Water electrolysis for hydrogen production requires highly active and inexpensive catalysts. Herein, we combine ultrasonic impact nanocrystallization (UIN) technology with nital etching method to rapidly prepare highly efficient self-supporting Cu electrode with abundant low-angle grain boundaries. When used as a catalyst for hydrogen evolution reaction (HER), the as-prepared electrode exhibits an overpotential of 353 mV at a current density of 10 mA cm-2, which is about 200 mV lower than that of the blank Cu plate. Moreover, the overpotential decreased to 246 mV after the stability test of 100 h, indicating a self-optimizing property. This work paves a new way for the preparation of self-supporting electrode with high performance.
Makola, Lekgowa C.Moeno, SharonOuma, Cecil N. M.Sharma, Ajit...
15页
查看更多>>摘要：Clean energy production and environmental detoxification through photocatalysis have received wide-spread attention due to their efficiency and capability to address global energy and environmental related calamities. Moreover, graphitic carbon nitride (g-C3N4) and many other single-semiconductor based pho-tocatalysts have been widely explored; however, their performance is still unsatisfactory. Herein, the engineering of g-C3N4 as a primary photocatalyst interlayered with niobium carbide (Nb2CTx) MXene co-catalyst for the formation of efficient photo-responsive Schottky-heterojunction photocatalyst is demon-strated. Visible-light absorption of g-C3N4 is proportional to the Nb2CTx contents. Moreover, g-C3N4 energy bandgap was significantly lowered from 2.61 eV to 2.19, 2.08, and 2.32 eV for 1, 3, and 5 wt% of Nb2CTx loaded onto g-C3N4, respectively. Nb2CTx MXene as a co-catalyst allows a formation of an efficient photo-catalyst with high potential to eliminate the use of costly noble metals. The devised Schottky-junction restrained the electron recombination rates threefold relative to the pristine g-C3N4. The conduction band potential of g-C3N4 and the composites were observed to be more positive in relation to the standard reduction potential of O-2/center dot O-2- (-0.33 V) CO2/CO (-0.53 V), CO3N4 (-0.24 V), H-2/H+ (0.0 V), signifying its merits potentials for photocatalysis. The observed charge carriers with more negative reduction potential facilitates efficient photocatalytic reactions, particularly in hydrogen production and catalytic transforma-tion of carbon dioxide into useful sources of energy. Fabricating a heterostructure between g-C3N4 and Nb2CTx MXene demonstrates the feasibility of facile preparation of photocatalysts with merit features due to synergistic catalytic effects. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：With the rapid development of the miniaturization and high-integration of electronic devices, conventional thermal conductive materials cannot ensure the safety and reliability of the high-power devices in working environments. It is urgent to develop thermal management materials with excellent thermo-physical and mechanical properties. In this work, the tungsten-coated graphite flakes (GFs(W)) were prepared by the immersion reduction, and the GFs(W) reinforced copper matrix composites (GFs(W)/Cu composites) were prepared by the vacuum hot-pressing sintering. Based on the microstructure and surface analysis, the W coating obtained at 900 & DEG;C and 200 g/L AMT appears the excellent surface structure and interfacial adhesion, which transfer the interfacial bonding from mechanical combination to mechanical-metallurgical synergy between the GFs and Cu. In addition, the volume fraction of W coating has a threshold to improve properties of the GFs(W)/Cu composites, in which the GFs(6 W)/Cu composites show the outstanding comprehensive performance: the in-plane thermal conductivity and flexural strength are 879.0 & PLUSMN; 10.0 Wm(-1)K(-1) and 166.9 & PLUSMN; 3.4 MPa respectively, which are improved by 22.3% and 356.0%, and the lowest coefficient of thermal expansion is 4.3 & PLUSMN; 0.5 ppmK(-1). To sum up, it provides an effective way to develop novel structural and functional integrated graphite/copper composites for thermal management. (c) 2022 Published by Elsevier B.V.
查看更多>>摘要：Blown-powder additive manufacturing process, directed energy deposition (DED) is applicable to scale-up material development with cost-effective elemental powder mixtures. In this paper, the effectiveness of applying DED to the design and synthesis of model CoCrFeNiTi high entropy alloys (HEAs) was demonstrated. Through a careful design of composition and delicate selection of particle size and shape, three CoCrFeNiTi HEAs with different microstructures were in-situ synthesized from premixed elemental powders. Transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction were used for microstructure characterization. H3-Co24.4Cr17.4Fe17.5Ni24.2Ti16.5 in at% (close to Co1.5CrFeNi1.5Ti) was fabricated with a soft face-centered cubic (FCC)-gamma phase structure while hard intermetallic phases such as sigma-FeCr, delta-NiTi2, and a small amount of Ni3Ti2 were precipitated and uniformed distributed in the FCC matrix for H1-Co22.2Cr16.1Fe19Ni21.8Ti20.9 and H2-Co25.9Cr15Fe17Ni20.8Ti21.3. With a large percent of the secondary phases, H1 exhibited a hardness value of about 853 HV0.5. These HEAs displayed a high oxidation resistance comparable to Inconel 625 superalloy. A detailed evaluation of the composition, microstructure, hardness, oxidation resistance, and wear resistance of these HEAs was conducted as compared with those of a reference HEA and two popular wear-resistant steels. (c) 2022 Elsevier B.V. All rights reserved.
查看更多>>摘要：Power generation from ethanol by solid oxide fuel cells (SOFCs) can be a clean and green way to utilize renewable fuel. In this study, the performance of the reduced La0.4Sr0.6Co0.2Fe0.7Nb0.1O3-delta (LSCFN) with anchored Co-Fe nanoparticles is investigated as the electrode in low concentration ethanol for the first time. The cell with the LSCFN as the symmetrical electrodes demonstrates considerable peak power density (0.32 W cm-2) and excellent durability (160 h) at 800 C. Moreover, the reduced LSCFN is further applied as a catalyst layer to prevent the Ni-YSZ anode-supported cell from coking in ethanol fuel. Interestingly, both cells modified with or without this LSCFN layer demonstrate similar output performance in H-2. While in ethanol, the catalyst layer modified cell exhibits better coking resistance and stability than the conventional cell, showing 0.97 W cm-2 at 800 C, as well as excellent durability for 210 h. The results suggest that combining the Ni-YSZ anode-supported cells with the excellent carbon tolerance of the LSCFN can clean and stable directly generate power from ethanol. (C) 2022 Published by Elsevier B.V.
查看更多>>摘要：In this article, we studied the magnetic and transport properties by magnetization, resistivity, and specific heat measurements for EuCu4As2 crystals with a rhombohedral structure. Strongly anisotropic magnetism and rich magnetic phases were observed under magnetic field in this compound. Interestingly, we observed two types of magnetoresistance: a large negative magnetoresistance (-55%, at 35 K, 9 T) near the magnetic transition temperature, due to reduction of magnetic scattering under magnetic field; a large positive magnetoresistance (60% at 2 K, 9 T) at lower temperatures when Eu2+ moments ordering ferromagnetically, similar to that observed in the non-magnetic isostructural analogue SrAg4As2 with possible nontrivial topological bands, which may be related to its special band structure.(c) 2022 Elsevier B.V. All rights reserved.
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