查看更多>>摘要：? 2022 Elsevier B.V.Perovskite fluoride is a potential electrode material for supercapacitors because its high theoretical specific capacitance. However, the relatively poor cyclic stability and rate performance limit its practical application. In this paper, we successfully synthesized the bimetallic perovskite fluorides/reduced graphene oxide (NaCo0.2Ni0.8F3/rGO) composite materials through a simple solvothermal method. The effects of the Co/Ni ratio regulation and the addition of rGO on the electrochemical properties of the perovskite composite materials have been investigated in detail. The variable valence metal ions by Co/Ni ratio regulation can lead to multiple redox reactions, which are helpful to improve the specific capacity of the materials. Meanwhile, the addition of rGO could improve the cycle stability and rate performance by virtue of the great conductivity of the rGO and the uniform dispersion of perovskite nanoparticles on it. The NaCo0.2Ni0.8F3/rGO composite electrode displays the high specific capacity of 805.7 C g?1, excellent rate performance (82% capacity retention from 0.5 to 16 A g?1) and superior cycle stability (92% retention over 5000 cycles). Furthermore, the active carbon//NaCo0.2Ni0.8F3/rGO asymmetric supercapacitor exhibits a high energy density of 52.19 Wh kg?1 under a power density of 750 W kg?1. It is believed that the above findings supply an efficient electrode design for the future practical application of perovskite fluorides in high-performance supercapacitor.
查看更多>>摘要：? 2022 Elsevier B.V.Silicon-based materials are expected to be the next generation of anode materials for lithium-ion batteries (LIBs). However, the electrode structure will be damaged due to large volume expansion during the lithiation process, resulting in a rapid decay of the battery performance. Nanostructures, porous structures, and carbon coatings have been shown to be effective in reducing the effect of volume expansion. In this work, porous carbon coated silicon (Si/PC) nanoparticles were prepared to suppress the effect of silicon volume expansion while improve the infiltration of electrolyte and the diffusion of lithium ions. The prepared Si/PC nanoparticles were mixed with commercial graphite in different mass ratios as anode materials for LIBs, which can effectively control the specific capacities of the anodes and help the practical applications by reducing the production cost. As the mass ratio of the prepared Si/PC nanoparticles to commercial graphite is 2:1, the first discharge specific capacity is 1586.3 mA h g?1 with an initial coulombic efficiency of 82.1% at a current density of 200 mA g?1. After 250 cycles at 1000 mA g?1, the capacity retention rate is 86.8%. The full cell with LiNi0.8Mn0.1Co0.1O2 as cathode shows an excellent cycle stability with a high stack cell energy density of 882.3 Wh/L.
查看更多>>摘要：? 2022 Elsevier B.V.The development of low-cost, durable and easily available electrocatalysts as alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR) will promote the large-scale commercial application of fuel cells and metal-air batteries. Among the transition metal based N4-metallomacrocyclic molecules, the Co macrocycle catalyst usually exhibits superior long-term durability and stability than the Fe family. Developing efficient Co-N4 ORR electrocatalyst is of great significance. In the work, fluorinated cobalt phthalocyanine (CoPcF16) were anchored on various carbon materials in different structural dimensions (1–3D) including 1D carboxyl carbon nanotube (CNT), 1D carbon nanofibers (CNF), 2D nitrogen doped graphene (N-G), and 3D ordered mesoporous carbon CMK-3, which were explored and investigated as electrocatalysts for ORR. The results show that the molecular CoPcF16 anchored on theses carbon materials exhibited different electrocatalytic activity with the increased half-wave potential (E1/2) order of CMK-3>CNT>N-G>CNF, which is related to oxo functionalities (axial coordination to Co), porous structures and defective sites. The CoPcF16-carbons hybrids exhibited much lower tafel slope and comparable E1/2 than commercial Pt/C catalysts for ORR. The prepared catalysts also demonstrated excellent stability even after 5000 cycling. CoPcF16-carbons hybrids will be potential candidates to replace Pt-based catalysts for PEMFCs applications in future.
查看更多>>摘要：? 2022 Elsevier B.V.Developing highly active and stable air electrode is crucial to large-scale commercialization of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein we report A-site Ca-doped layered double perovskites, Pr1-xCaxBa0.94Co2O5+δ (PCxB0.94C, x = 0.1–0.3), as a family of promising cathode materials for catalyzing the oxygen reduction oxygen (ORR). Benefiting from enhanced electrical conductivity and promoted surface oxygen exchange/chemical diffusion rates, Pr1-xCaxBa0.94Co2O5+δ demonstrates an efficient ORR activity in intermediate-temperature region. The electrochemical performance of the samples is characterized by symmetrical half-cells and button fuel cells. Among all these compositions, Pr0.8Ca0.3Ba0.94Co2O5+δ (PC0.3B0.94C) exhibits the lowest polarization resistance (Rp) of 0.027 Ω cm2 at 700 °C. The peak power density (PPD) of 1114 mW cm-2 is achieved in the PC0.3B0.94C cathode-based button fuel cell at 700 °C, along with outstanding stability over a period of 130 h. The findings endow the potential utilization of the PC0.3B0.94C cathode for IT-SOFCs under the realistic conditions.
查看更多>>摘要：? 2022 Elsevier B.V.The combined effect of chemical doping and grain orientation on the thermoelectric properties of delafossite-type CuFeO2 ceramics was investigated. Ni was chosen as the dopant, whereas the reactive templated grain growth method was used for the fabrication of grain-oriented bulk ceramics. Nanorods of Ni-doped α-FeOOH with a nominal Ni content of up to 5 mol% were synthesized by the hydrothermal method and were then used as the template to fabricate Ni-doped CuFeO2 ceramics with a preferred c-axis orientation. The electrical conductivity, Seebeck coefficient, and thermal conductivity of the Ni-doped CuFeO2 ceramics along the in-plane direction (perpendicular to the orientation axis) were measured at temperatures between 300 and 1100 K. Ni doping was found to effectively increase the electrical conductivity and decrease the thermal conductivity, whereas it maintained a high Seebeck coefficient of around 400 μV K?1. Consequently, the c-axis-oriented CuFeO2 ceramics doped with 1 and 3 mol% Ni showed an enhanced dimensionless figure of merit of 0.08 at 900 K.
查看更多>>摘要：? 2022The utilization of non-precious and noble-metal free catalysts for the photo conversion of water into hydrogen is of significant interest. In particular, the typical layered MoS2 has attracted interest as a low-cost alternative to platinum in the photocatalytic hydrogen evolution system. However, theoretical studies have suggested that the activity of the MoS2 co-catalyst arises only at the S sites on the edges of grains, and not on the basal planes. In this respect, the doping of a foreign metal into the MoS2 system is an interesting method for boosting the hydrogen production rate by increasing the conductivity and number of active sites. Herein, simple methods are used to decorate CdS nanorods with earth-abundant, few-layered zinc-doped MoS2 nanosheets (Zn-MoS2/CdS), and the so-obtained Zn-MoS2/CdS composite is used for the photocatalytic hydrogen evolution reaction under solar irradiation in the presence of lactic acid as a hole scavenger. Thus, the catalyst is shown to provide significant hydrogen generation activity, along with excellent and continuous photo stability for more than 60 h under optimal conditions. Moreover, the hydrogen evolution rate of the Zn-MoS2/CdS composite is up to ~75-fold greater than that of the pure CdS. The loading of Zn-MoS2 is shown to increase the synergistic effects of the photocatalyst due to the effective separation of charge carriers, extensive exposure of catalytic sites, and high dispersion of the few-layered Zn-MoS2. In addition, the stability of the optimized material is enhanced by the doping of Zn metal into the MoS2. To the best of our knowledge, the hydrogen evolution activity of the as-prepared composite is the highest ever reported for the CdS and single metal-doped MoS2-based catalysts. Hence, this type of Zn-MoS2/CdS composite is strongly believed to have great potential as a low-cost, highly-efficient, noble-metal free catalyst for the photocatalytic reduction of water.
查看更多>>摘要：? 2022 Elsevier B.V.A two directional high thermal conductive carbon fiber reinforced aluminum matrix composite with low interface damage is prepared by a vacuum hot-pressure diffusion method using the mesophase-pitch-based carbon fiber (CFMP) cloth as fast heat conduction channels. The fiber/matrix interface is composed of an amorphous gradient transition layer between aluminum matrix and CFMP rather than Al4C3 interface phase, thus endowing the continuous heat conduction channels in the composite. The composites deliver the high thermal conductivity of 305.5 W?m?1?K?1 in the X (Y) direction and the low volume density of only 2.53 g?cm?3 when the fiber volume fraction reaches 30 vol%. The high thermal conductivity of the composite is attributed to the highly oriented fast heat transfer effect of the CFMP, the isotropic heat transfer effect of the aluminum matrix and the low-damage CFMP/aluminum interface. This study opens a new avenue to design and select the high thermal conductivity and lightweight thermal management materials for the aerospace field.
查看更多>>摘要：? 2022 Elsevier B.V.Based on the Monte Carlo method and using the Ising model, the magnetic as well as the magnetocaloric properties of lacunar compounds La1-xxMnO3 (x = 0.1 and 0.2) were investigated. Free boundary conditions for our system were applied to simulate the 3D-Ising Hamiltonian of these systems. Cubic magnetic sublattices of size L3, with L = 20, 24 and 28, were investigated in this study to compute the magnetization and the magnetic susceptibility as a function of temperature (T) at various applied fields. In order to calculate the variation of the magnetic entropy versus the applied magnetic field, we have examined an isothermal process by considering a term of magneto-crystalline anisotropy. In order to validate the results, many parameters were calculated. The results obtained are in good agreement with the experimental ones. The high relative cooling power values of our compounds leads to promising material for magnetic refrigeration technology. This material could be considered as a good candidate for applications requiring high values of TC.
查看更多>>摘要：? 2022 Elsevier B.V.Carbon nanomaterials (such as graphene, carbon nanotubes and nano-diamond) are widely used to synthesize metal matrix composites to strengthen metals such as Ti, Al and Cu. However, severe aggregation of these nano-scale reinforcements within the metal matrix has been a serious issue to achieve good performance metal matrix composites. In this study, we employed an in-situ co-precipitation method to decorate reduced graphene oxides with aluminium oxide nanoparticles (i.e. rGONs@Al2O3), which were then introduced into Ti-6Al-4 V matrix using the processes of ball milling and spark plasma sintering. Effects of co-precipitation temperature on the characteristics of rGONs/Al2O3 nanopowders, and their concentrations on microstructures and mechanical properties of the composites were systemically investigated. Characterization results revealed that γ-Al2O3 nanoparticles were uniformly wrapped with rGONs fakes, and numbers and sizes of Al2O3 nanoparticles were decreased with the increase of co-precipitation temperature. The rGONs@Al2O3 nanoparticles were uniformly coated onto the surfaces of the Ti-6Al-4 V powders, thus achieving a much finer grain size of matrix after the sintering process. As the content of rGONs@Al2O3 was increased, the strength of the composites was enhanced, whereas the elongation was slightly decreased. Due to effects of grain refinement and effective load transfer, the composite of 0.5 wt% rGONs@Al2O3 has achieved a high yield strength and an ultimate tensile strength of 950 MPa and 1022 MPa, which were ~120.4% and ~117.1% of the TC4 matrix, respectively. The fracture morphology was a mixture of cleavage fracture and ductile fracture.
查看更多>>摘要：? 2022 Elsevier B.V.Good interfacial compatibility is essential to grow intermetallic compound layer on the surface of substrates for the potential application of electrocatalytic reactions. Here, an interface strategy is proposed to prepare a free-standing copper-cobalt-nickel nitride electrode，in which copper-cobalt-nickel nitride is anchored on hydrophilic treated nickel foam. Compared to bi-metal hierarchical catalysts, the as-fabricated epitaxial heterostructure shows excellent oxygen evolution reaction (OER) activity with an ultralow overpotential of 190 mV, as well as an overpotential of 63 mV for hydrogen evolution reaction (HER) at the current density of 10 mA cm–2. Most importantly, the modified tri-metal nitrides exhibit improved interfacial compatibility due to the interfacial defects, which can increase electron transport across the junction during the catalytic reactions. Density functional theory calculations reveal that the synergistic effect between copper, cobalt, and nickel nitride creates a proper electronic structure that lowers the reaction barriers of HER/OER.
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