Latest ArticlesA novel Pd-Fe/α-Al2O3 catalyst was synthesized by incipient-wetness impregnation method with bayberry tannin as chelating promoter and commercial hollow column Raschig ring α-Al2O3 as support for the synthesis of diethyl oxalate from CO and ethyl nitrite. A variety of characterization techniques including N2 physical adsorption, optical microscopy, scanning electron microscopy and energy dispersive system (SEM-EDS), inductively coupled plasma optical emission spectroscopy (ICP-OES), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), were employed to explore the relationship between the physicochemical properties and activity of catalysts. It indicated that a large number of phenolic hydroxyl groups in bayberry tannin can efficiently anchor the active component Pd, reduce the particle size and make the active Pd as a multi-ring distribution on the commercial α-Al2O3 support, which were beneficial to improve the catalytic activity for the production of diethyl oxalate from CO and ethyl nitrite. 0.3 wt% Pd-Fe/α-Al2O3 showed excellent catalytic activity and selectivity in a continuous flow, fixed-bed reactor with the loading amount of 10 mL catalysts. Under the mild reaction conditions, the space-time yield of diethyl oxalate was 978 g L-1 h-1 and CO conversion was 44% with the selectivity to diethyl oxalate of 95.5%.
Research on pollution characteristics and toxicities of emerging polycyclic aromatic sulfur heterocycles (PASHs) in PM2.5 has not been reported due to the lack of analytical method with the needed performance. In the present study, a novel method for the determination of 14 PASHs in PM2.5 was developed using atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS). Atmospheric pressure chemical ionization was operated with multiple reaction monitoring in positive ionization mode. High sensitivity (method detection limit < 1.673 pg/m3), acceptable recoveries (67.6%–120.8%) and precisions (RSD of 2.2%–15.4%) were obtained. The method was successfully applied for analyzing PASHs in 10 PM2.5 samples collected from Taiyuan, a typical industrial city in China, in 2016. The total concentrations were from 929 pg/m3 to 14,593 pg/m3. The determined levels indicated that further investigations on environmental fate and toxicities of PM2.5-bound PASHs may be needed.
Realizing nitrogen reduction reaction (NRR) to synthesis NH3 under mild conditions has gained extensive attention as a promising alternative way to the energy- and emission-intensive Haber–Bosch process. Among varieties of potential strategies, photoelectrochemical (PEC) NRR exhibits many advantages including utilization of solar energy, water (H2O) as the hydrogen source and ambient operation conditions. Herein, we have designed a solar-driven PEC-NRR system integrating high-efficiency Fe2O3-based photoanode and atomically dispersed cobalt (Co) cathode for ambient NH3 synthesis. Using such solar-driven PEC-NRR system, high-efficiency Fe2O3-based photoanode is responsible for H2O/OH- oxidation, and meanwhile the generated photoelectrons transfer to the single-atom Co cathode for the N2 reduction to NH3. As a result, this system can afford an NH3 yield rate of 1021.5 μg mgCo-1 h-1 and a faradic efficiency of 11.9% at an applied potential bias of 1.2 V (versus reversible hydrogen electrode) on photoanode in 0.2 mol/L NaOH electrolyte under simulated sunlight irradiation.
In this study, large-scale Te-doped polycrystalline SnSe nanopowders were synthesized by a facile hydrothermal approach and the effect of Te doping on the thermoelectric properties of SnSe was fully investigated. It is found that the carrier concentration increases due to the reduction of band gap by alloying with Te, which contributes to significant enhancement of electrical conductivity especially at room temperature. Combined with the moderated Seebeck coefficient, a high power factor of 4.59 μW cm−1 K−2 is obtained at 773 K. Furthermore, the lattice thermal conductivity is greatly reduced upon Te substitution owing to the atomic point defect scattering. Benefiting from the synergistically optimized both electrical- and thermal-transport properties by Te-doping, thermoelectric performance of polycrystalline SnSe is enhanced in the whole temperature range with a maximum ZT of ~0.79 at a relatively low temperature (773 K) for SnSe0.85Te0.15. This study provides a low-cost and simple low-temperature method to mass production of SnSe with high thermoelectric performance for practical applications
The development of high-performance and cost-effective electrocatalysts towards oxygen reduction reaction (ORR) is of significant importance, but still challenging for the practical applications in related energy systems. ORR process typically suffers from sluggish kinetics, the exploration of ORR electrocatalyst thus requires elaborate design. Herein, an effective strategy is developed for growing Co/N-doped carbon nanotube arrays on 2D MOFs-derived matrix via the pyrolysis of Co/Zn metal-organic-framework (MOF) nanosheets. The Co/Zn-MOF nanosheets serve as both the self-template for the 2D carbonized framework morphology and C/N source for the in-situ growth of 1D N-doped carbon nanotubes. The constructed hierarchical architecture effectively integrates the 0D/1D Co nanoparticle/N-doped carbon nanotube interface and 1D (nanotubes)/2D (nanosheets) junction into frameworks with highly exposed active surface, enhanced mass-transport kinetics and electrical conductivity. As a result, the designed composite exhibits superior ORR activity and durability in alkaline media as compared to commercial Pt/C. Particularly, it shows promising ORR performance with a half-wave potential of 0.78 V versus reversible hydrogen electrode and negligible activity attenuation after 5000 potential cycles in acidic electrolyte. The designed strategy can be extended to construct other MOFs-derived carbon matrixes with diverse hierarchical structures and provide an efficient avenue for searching high-performance electrocatalysts.
Controlling ions transport across the membrane at different pH environments is essential for the physiological process and artificial systems. Many efforts have been devoted to pH-responsive ion gating, while rarely systems can maintain the rectification in pH-changing environments. Here, a composite nanochannel system is fabricated, which shows unidirectional rectification with high performance in a wide pH range. In the system, block copolymer (BCP) and polyethylene terephthalate (PET) are employed for the amphoteric nanochannels fabrication. Based on the composite system, a model is built for the theoretical simulation. Thereafter, rectification mapping is conducted on the system, which can provide abundant information about the relations between charge distribution and ions transport properties. The proposed rectification mapping can definitely help to design new materials with special ion transport properties, such as high-performance membranes used in the salinity gradient power generation field.
Flexible Na-ion storage cathodes are still very few due to the challenge in achieving both reliable mechanical flexibility and excellent electrochemical performances. Herein, a new type of flexible Na3(VOPO4)2F cathode with nanocubes tightly assembled on carbon cloth is fabricated by a facile solvothermal method for the first time. The cathode is able to exhibit superior rate capability and stable cycling performance up to 1000 cycles, due to the surface-assembling of crystalline nanocubes on carbon fibers. In addition, it shows good mechanical flexibility, nearly no capacity decay is observed after continuous bending of 500 times. With this novel cathode and a directly-grown Na2Ti2O5 anode, a fully binder-free Na-ion battery is assembled. It can deliver a high working voltage and increased gravimetric energy/power densities (maximum values: 220.2 Wh/kg; 5674.7 W/kg), and can power a LED indicator at bending angles from 0° to 180°.
Electrical double-layer capacitors are widely concerned for their high power density, long cycling life and high cycling efficiency. However, their wide application is limited by their low energy density. In this study, we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon (CoAT-NC) material. Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix, which is benefit for improving electrical conductivity and density of states of the carbon material. Therefore, an enhanced performance is expected when CoAT-NC is served as electrode in a supercapacitor device. CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte. Furthermore, a good energy density of 30 Wh/kg can be obtained in the organic electrolyte.
Hydrous electrolytes with high electrochemical potentials were obtained by hydrating water molecules into solutes to form high Li: water molar ratio electrolytes (HMRE). Solid polyethylene glycol (PEG) were employed to enhance the molar ratio of Li+ to water in the electrolytes while reducing the consumption of Li-salt. The obtained mole ratio of Li+ to water molecules in the hydrous electrolytes was greater than 1:1; however, the mass fraction of Li-salt was reduced to 61% (approximately 5.5 mol/kg, based on water and PEG). Compared with that of water-in-salt electrolytes, the mass fraction of Li-salt could be remarkably reduced by adding solid PEG. The electrochemical stability of the electrolytes improved considerably because of the strong hydration of Li+ by the water molecules. A beneficial passivation effect, arising from the decomposition of the electrolyte, at a wide potential window was observed.
A new family of isostructural 3d-4f polymetallic complexes, formulated as [Cu6Ln5(μ3−OH)9 (C4H8O2N)6(C5H4ON)6(H2O)9]·(ClO4)6·(H2O)22 (Ln = Pr, 1; Nd, 2; Sm, 3; Eu, 4; Gd, 5), was successfully isolated through the simple hydrolysis reaction of 2-aminoisobutyric acid, 2-hydroxypyridine, Cu(CH3COO)2·H2O, and Ln(ClO4)3·6H2O. Notably, the [Cu6Ln5] clusters with high molecular symmetry of D3h are rare examples of 2-aminoisobutyric acid-based 3d-4f clusters. The successful theoretical modeling of 5 yielded that the Gd-Gd exchange is of order 0.2 K, whereas the Gd-Cu exchange is an order of magnitude larger. Magnetization data collected for complex 5 yield a magnetic entropy change (−ΔSm) of 19.6 J kg−1 K−1 at 3 K and 7 T, which may be attributed to the weak magnetic interactions between the component metal ions.
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