Search

A metal-organic framework (Cu 3 (BTC) 2 , BTC = 1,3,5-benzenetricarboxylate) composite based on polyoxometalate (H 6 P 2 W 18 O 62 ) was synthesized by a simple one-pot solvent-thermal method and applied as an adsorbent to remove methylene blue (MB) from aqueous solution. The chemical structure, morphology and thermostability of the composite were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscope (SEM), Thermogravimetric Analysis (TG) and N 2 adsorption–desorption isotherms. The removal rate of the composite H 6 P 2 W 18 O 62 @Cu 3 (BTC) 2 was greater than that of the pure Cu 3 (BTC) 2 , especially at higher initial concentrations, showing that the adsorption performance of porous Cu 3 (BTC) 2 can be improved through the modification of H 6 P 2 W 18 O 62 . The effect factors containing the initial concentration, contact time, initial solution pH and temperature of MB adsorption onto the composite were systematically explored. The experimental isotherm data was found to fit the Freundlich model well and the process of MB adsorption onto H 6 P 2 W 18 O 62 @Cu 3 (BTC) 2 was controlled by the pseudo-second-order kinetic model. The thermodynamic parameters illustrated that the adsorption was spontaneous and exothermic process. These results show that designing a metal-organic framework composite is a quite promising strategy to achieve extreme application for metal-organic framework. [ABSTRACT FROM AUTHOR]

Skutterudite CoSb 3 material exhibits excellent thermoelectric properties for thermoelectric application. In this work, CoSb 3 thin films were fabricated by direct current magnetron co-sputtering. The composition of thin films was controlled by regulating the deposition power of both Co and Sb. Then the as-deposited Sb-excess sample was chosen to process post-annealing. High-resolution transmission electron microscopy and X-ray diffraction, together with Raman analysis, demonstrate that the annealed samples have well-crystallized and nano-sized skutterudite CoSb 3 structure. Hall measurement shows that specimens are P-type semiconductor. Both of the increasing of Seebeck coefficient and electric conductivity can be obtained when the samples annealed at appropriate temperature, indicating that thermally can improve its thermoelectric properties due to well-crystallized and nano-sized structure. [ABSTRACT FROM AUTHOR]

Cu doped ZnSb based thin films were deposited by direct current magnetron co-sputtering. X-ray diffraction results show that the un-doped thin film reveals a single ZnSb phase and it transforms to Zn 4 Sb 3 phase after Cu doped. The material with Zn 4 Sb 3 phase which belongs to R-3c space group crystal will lead to lower thermal conductivity. The Hall effect measurement shows that the samples are P-type semiconductors. The electrical conductivity increasers after Cu doped due to the increase of carrier concentration and the improvement in crystallinity. Though the Seebeck coefficient decreases after Cu doped, the ZT value increases from 0.11 to 0.43 with higher electrical conductivity and lower thermal conductivity at room-temperature. The temperature-dependent of ZT value is estimated to be ∼1.35 for the thin film with Zn 4 Sb 3 phase by using the bulk lattice thermal conductivity together with the thin film electrical thermal conductivity. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) has been widely used in bandpass filters for wireless communication applications, but its low electromechanical coupling factor (k t 2 ) limits the bandwidth of the filter based on it. In this work, AlN alloys incorporated with various transition metals are theoretically studied, and Mo-alloy AlN (Mo x Al 1−x N) is predicted to be more prominent in improving k t 2 . Furthermore, the influence of Hubbard U correction on the k t 2 of Mo x Al 1−x N is discussed, and the correction is found to show a crucial role at a high x. The magnitude of k t 2 is more correlated with the piezoelectric stress constant e 33 , and both of them depend on the distribution of Mo atoms. The contribution of each atom to piezoelectric performance is described by an effective displacement-response internal-strain parameter Γ 33 in this work, which is generally proportional to internal parameter u and response of u to applied strain along the z -axis. The increase of k t 2 is ascribed to the Mo-induced larger u and Γ 33 , but the Mo dimer and line along the z-axis weaken the increase mechanism. To obtain a high k t 2 , it is better to alloy Mo atoms into more sublayers of AlN and with fewer Mo dimers and lines along the z -axis. The behavior that the Mo atoms distributed evenly in the xy plane is also beneficial. A high k t 2 of 37.8% is predicted in a special quasirandom configuration of Mo 0.167 Al 0.833 N, which might be the highest value reported to date for the AlN alloys. [Display omitted] • Mo-alloy AlN outperforms other alloys in enhancing the k t 2 of AlN. • A high k t 2 of 6.87 times that of pure AlN is predicted. • The magnitude of k t 2 depends on the distribution of Mo atoms in Mo x Al 1−x N. • Γ 33 is used for the first time to explain the contribution of each atom to k t 2 . [ABSTRACT FROM AUTHOR]

The oxygen reduction reaction (ORR) plays a significant role in energy conversion technologies such as metal-air batteries and fuel cells. The development of efficient ORR electrocatalyst is highly desirable to achieve the fast oxygen reduction. In this work, the bimetallic Cu and Co embedded nitrogen-doped carbon (CuCo-N/C) is fabricated as efficient electrocatalyst for ORR. The incorporation of Cu-precursor into Co-based zeolitic imidazolate frameworks (ZIF) is innovated here to synergistically enhance the activity of Co. Surprisingly, the addition of Cu can also increase the nitrogen content in the CuCo-N/C catalysts, which could generate more active sites and result in the improvement of ORR activity. The optimized CuCo-N/C catalysts exhibit superior ORR performance with a half-wave potential of 0.85 V (vs. RHE), a limiting current density of 5.61 mA cm−2 and enhanced long-term durability comparing with the state-of-the-art Pt/C catalysts. Benefiting from the unique structure, the as-made CuCo-N/C catalysts as electrode for Zn-air battery delivers excellent performance with a peak power density of 66.9 mW cm−2, a high open circuit voltage of 1.468 V, and a voltage degradation of about 1.4% after 12 h discharging, which is much better than that of Pt/C catalysts. • A CuCo-N/C catalyst is obtained by a fast and efficient microwave-assisted method. • High N content and bimetallic Cu/Co contribute to the enhanced ORR performance. • The CuCo-N/C electrode delivers excellent performance in Zn-air battery. [ABSTRACT FROM AUTHOR]

Tin selenide (SnSe) is a very promising thermoelectric material, but there are few reports related to the thermoelectric properties of its thin films, especially for n-type SnSe. In this work, n-type SnSe thin films were synthesized via thermal evaporation using powdered SnSe that was prepared directly by mechanical alloying. It was found that the crystallinity of the films gradually improved and the closer the elemental ratio of Sn and Se was to a ratio of 1:1 with increasing the current through the tungsten boat during the thermal evaporation of the SnSe precursor from 100 to 130 A. Further, the thin films obtained at 120 A show the highest power factor (0.13 μW/mK 2 ) of all the samples fabricated in this study. The samples were then annealed, and the thermoelectric properties of the films were enhanced as this step improved their crystallinities. A Seebeck coefficient of over 100 μV/K could be achieved with an annealing time of 4 h. Combined with a recorded electrical conductivity of 47 S/cm, a maximum power factor of 120 μW/mK 2 at 473 K has been obtained for the annealed film with n-type conductive characteristics; this is nearly six times higher than that reported for polycrystalline n-type bulk SnSe at the same temperature. [ABSTRACT FROM AUTHOR]

Cuprous oxide (Cu 2 O) thin films co-doped with zinc (Zn) and indium (In) were fabricated with direct current (DC) magnetron sputtering. The sputtering voltage of the Cu target was fixed while that of the alloy target of Zn and In was varied. It is found that when the alloy target voltage is below 310 V, pure-phase Cu 2 O can be obtained while a further increase in the alloy target voltage will result in the presence of metallic copper. The surface morphologies, the atomic ratios of the Zn and In, and the grain size do not have a linear dependence on the sputtering voltage of the alloy target. Higher concentration doping will decrease the lattice constant of Cu 2 O. Pure-phase samples doped with Zn and In have relatively higher transmittance and larger optical band gaps. The n-type conduction of Cu 2 O co-doped with Zn and In is realized when the sputtering voltage of the alloy target is 310 V. Zn and In atoms are found to exist as Zn 2+ and In 3+ in the films and they are possible donors for the n-type conduction. [ABSTRACT FROM AUTHOR]

In this study, copper selenide thin films were fabricated by ion beam sputtering deposition by using a fan-shaped target of Cu and Se. The influence of heat treatment on thermoelectric properties of copper selenide thin films was investigated. X-ray diffraction results demonstrate that the as-deposited and annealed thin films are both amorphous. The SEM images show that the thin films are discontinuous and just like island structure. The thin films are crystalline when the substrate temperature is added at the deposition process. The thin film exhibits the dominating CuSe phase at the substrate temperature of 250 °C and it transforms to single CuSe 2 phase at the temperature of 300 °C. When the substrate temperature further increased to 350 °C, the mixed Cu 2−x Se phase is dominated. The thin film with Cu 2−x Se phase has a high electrical conductivity of 2.02 × 10 4 Scm −1 at 423 K and thin film with CuSe 2 phase has a high Seebeck coefficient of 37.3 μVK −1 at 316 K. [ABSTRACT FROM AUTHOR]

Transition metal oxides have obtained considerable research attention in energy storage devices. In this study, we demonstrate the preparation of hierarchical CoMn 2 O 4 @Ni(OH) 2 nanowire arrays (CoMn 2 O 4 @Ni(OH) 2 /Ni) by a combination of hydrothermal reactions and annealing process. This hybrid CoMn 2 O 4 @Ni(OH) 2 /Ni electrode possesses a significantly enhanced capacity of 8.5 F cm−2 at 1 mA cm−2 (3017.9 F g−1 at 0.4 A g−1). Additionally, the assembled all-solid-state asymmetric supercapacitor (CoMn 2 O 4 @Ni(OH) 2 /Ni//AC ASC) displays a comparable energy density of 76.2 Wh kg−1. Meanwhile, the prepared CoMn 2 O 4 @Ni(OH) 2 /Ni anode revealed initial discharge capacity (~3548.2 mAh g−1). After 50 cycles, the CoMn 2 O 4 @Ni(OH) 2 /Ni anode also shows a satisfied cycling stability (1437.4 mAh g−1 of capacity maintained). Further, the LED devices can be lit up for more 230 min by the assembled CoMn 2 O 4 @Ni(OH) 2 /Ni cell. Therefore, this novel CoMn 2 O 4 @Ni(OH) 2 /Ni materials with excellent electrochemical property have great potential in the high energy storage applications. [Display omitted] • The rough surface of nanowires enhances the binding force with nanosheets and improve the cycling stability. • The ultra-thin Ni(OH) 2 nanosheets can protect the internal CoMn 2 O 4 nanowires and possess large surface area. • The hybrid electrode reveals good electrochemical performance in both supercapacitors and Li ion batteries. [ABSTRACT FROM AUTHOR]

NiCo x P @ NiCo-LDH catalysts are prepared by phosphating NiCo nanosheets on NiCo-layered double hydroxide (LDH) with multi-layer heterostructure. The NiCo x P @ NiCo-LDH could undergo electrocatalytic hydrogen evolution from the methanol/water mixture and value-added formate co-production. During the electrocatalytic reactions, the phosphating NiCo x P nanosheets could greatly improve the electron transfer efficiency, and it has a synergistic effect with heterostructures to enhance the electrocatalytic performance. During the hydrogen evolution and methanol oxidation reactions, the potential is only 0.132 and 1.23 V when the current density reaches 10 mA cm−2. Meanwhile, the NiCo x P @ NiCo-LDH symmetric two-electrode electrolyzer has a lower potential of only 1.43 V at a current density of 10 mA cm−2 and the Faraday efficiency of the production of formate and H 2 is nearly 100%. The electrocatalysts also display excellent stability during the water/methanol co-electrolysis. [Display omitted] • NiCo x P @ NiCo-LDH was prepared using a simple electrochemical deposition method. • The NiCo x P @ NiCo-LDH exhibits superior electrocatalytic activity and long-term stability. • The selectivity of the methanol oxidation reaction is high and the product is value-added formate. • The catalyst shows excellent catalyst activity because of the synergistic effect of Ni and Co and abundant active sites. [ABSTRACT FROM AUTHOR]

In filled CoSb 3 thin films with various In content were prepared on flexible substrates by multi-step co-sputtering method, which provided a promising way to prepare low-cost and high performance thin films. The influence of In content on the microstructure and thermoelectric properties of the CoSb 3 based thin films are systematically investigated. The thin film transforms from P -type to N -type with the increasing of In content. Both of the electrical conductivity and the Seebeck coefficient of the thin films increase after In filled. The thermal conductivity of the In filled thin film significantly decreases and the ZT value of the In-filled thin films are much higher than that of the unfilled thin film. It can be observed that the In filled thin films are single CoSb 3 phase and the grain size increases after In filled. The average grain size of all the thin films are less than 50 nm, indicates the thin films are nano-particles structure. [ABSTRACT FROM AUTHOR]

The self-catalytic growth of Al x Ga 1 − x N nanowires by chemical vapor deposition (CVD) with Ga, Al and NH 3 as the source materials and sapphire (0 0 0 1) as the substrates was studied. The Al mass, the distance between Al and Ga, and the growth temperatures have an influence on the morphologies of the samples. Without Ga, no nanowires are obtained. The Al content x in Al x Ga 1 − x N nanowires hardly changes with the starting mass of Al but slightly decreases with the increase in the growth temperature. We propose that it is Ga that acts as the catalyst during the self-catalytic growth of Al x Ga 1 − x N nanowires since the higher desorption rate of Ga and the N rich condition result in the island growth of GaN on sapphire and the island growth mode favors the formation of nanowires with the incorporation of Al. The Al content x in Al x Ga 1 − x N nanowires relies on the ratio of the saturation vapor pressure of Al to the sum of that of Ga and Al. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zn–Sb thin film was synthesized by using ternary layers annealing method. [•] Zn composition can be effectively controlled after heat treatment by using this approach. [•] Thin film with Zn4Sb3 as secondary phase has highest power factor at 300°C. [ABSTRACT FROM AUTHOR]

Design and synthesis of multi-functional electrocatalysts with high efficiency and low cost to replace noble metals are significantly important to realize new energy technologies. Herein, we report CuCo 2 S 4 hollow nanoneedle arrays as efficient trifunctional electrocatalysts for overall water splitting and aluminium-air batteries. CuCo 2 S 4 hollow nanoneedle arrays are grown on Ni foam (NF) via a facile hydrothermal method. Benefiting from the porous and hollow structure to expose more active sites, the CuCo 2 S 4 /NF hollow nanoneedle arrays exhibit superior electrocatalytic performance for hydrogen evolution (HER), oxygen evolution (OER), oxygen reduction reactions (ORR) in alkaline electrolytes. The corresponding experimental HER and OER overpotentials of CuCo 2 S 4 /NF catalyst are 61 mV and 189 mV at 10 mA cm−2 in 1.0 M KOH. In an assembled primary Al-air battery, the CuCo 2 S 4 /NF catalysts demonstrate an outstanding peak power density of 160 mW cm−2. This work provides a new strategy for developing non-noble metal multiple-functional catalysts for energy conversion and energy storage devices. Image 1 • Hollow nanoarrays copper-cobalt intermetallic sulfide on Ni foam are synthesized. • CuCo 2 S 4 exhibit synergistic electrocatalytic activity for HER, OER and ORR. • Al-air batteries self power the two-electrode configuration during water splitting. [ABSTRACT FROM AUTHOR]

Bismuth telluride (Bi 2 Te 3) is an efficient thermoelectric material, and fabricating Bi 2 Te 3 thin films with good thermoelectric properties is a prerequisite to realizing the potential of these materials in microdevice application. Controllable content deposition and low-negative thermal treatment are the two main challenges in preparing high-performance thin films. In this study, stoichiometric Bi 2 Te 3 thin films were successfully fabricated via the two-step thermal vapor process with a single evaporation source. Then, the rapid thermal process, which could avoid component loss, was used to further improve the crystallinity and thermoelectric properties of thin films. The Seebeck coefficient of Bi 2 Te 3 thin films clearly increased after rapid heat treatment, leading to enhanced power factor and good flexibility. Such thin films exhibited low thermal conductivity due to their nano-sized grains, resulting in high ZT of flexible Bi 2 Te 3 thin films. • Stoichiometric Bi 2 Te 3 thin films were successfully fabricated via the two-step single-source thermal evaporation. • Rapid thermal process was used to further improve the crystallinity and thermoelectric properties of thin films. • The Seebeck coefficient of the thin films increased after rapid heat treatment, leading to enhanced power factor. • Thin films exhibited low thermal conductivity due to their nano-sized grains, resulting in high ZT value. [ABSTRACT FROM AUTHOR]