查看更多>>摘要：? 2022 Elsevier B.V.Dedicated thermal treatments can improve the mechanical behaviour of high entropy alloys (HEAs) by producing nanostructured microstructures with improved characteristics. Herein, the inherent metastability of an equiatomic CoCuFeMnNi alloy was exploited to induce the formation of secondary phases upon ageing treatment. Advanced characterization techniques, namely high resolution synchrotron X-ray diffraction and aberration corrected scanning transmission electron microscopy, allowed to describe the decomposition of the supersaturated solid solution. Nanometric rounded Cu-rich clusters in the solution-treated alloy and coherent, regularly oriented Cu-rich discs in the peak-aged condition were possibly produced by spinodal decomposition. An almost 100% enhancement of mechanical strength was obtained thanks to the modulation of composition. Moreover, mechanical behaviour at cryogenic temperature was improved by ageing, both in terms of strength and ductility. Plastic deformation took place by dislocation slip, regardless of the testing temperature.
查看更多>>摘要：? 2021 Elsevier B.V.Thermoelectric materials based on Cu1.8S are not hampered by electric-field-driven degradation in real applications, but their high-temperature applications are problematic owing to their tendency to oxidize or spontaneously decompose. Here, we reveal that Cu1.8S powder is gradually oxidized to form a mixture of Cu2O, Cu(SO4), and Cu2O(SO4) at high temperatures under air. Although a dense oxide film is formed on the surface of the sintered Cu1.8S block at high temperature, hindering the oxidation process, the brittle oxide film fails to inhibit the spontaneous decomposition of the Cu1.8S block into the Cu1.96S phase and S vapor at high temperatures. Thus, Cu1.8S thermoelectric materials are unsuitable for applications above 300 °C in air. To address this issue, we partially replaced S atoms with Se; the sintered Cu1.8S0.8Se0.2 blocks exhibited significantly increased anti-oxidation and anti-decomposition capacities in air. In addition, we found that the thermoelectric figure of merit of the sintered Cu1.8S0.8Se0.2 block was 47% higher than that of traditionally prepared, pure Cu1.8S at 450 °C.
查看更多>>摘要：? 2022 Elsevier B.V.CeOx-MnOx/TiO2 (CMT) is the prototype, low-temperature (150–250 ℃) mixed oxide NH3-deNOx catalyst with the greatest potential for industrial application. The improvement of ultra-low temperature (60–150 ℃) denitration activity, SO2 and alkali resistance of CMT catalysts received significant attention. RuOx has been widely utilized in selective catalytic oxidation (SCO), and we believe that the catalyst must first undergo SCO before selective catalytic reduction (SCR). Therefore, a series of RuOx-CMT catalysts were prepared by impregnating RuOx with CMT as the carrier and their catalytic mechanism at low temperature and activity analyzed in detail through XRF, XRD, BET, TEM, HRTEM, STEM+EDS, XPS, H2-TPR, NH3-TPD-MS and in situ DRIFTS characterizations. The obtained results show that RuOx modification significantly improved the low-temperature denitrification activity of CMT by enhancing the interaction of Ce, Mn and Ti, promoting the conversion of inactive bidentate nitrate to the active monodentate nitrate and strengthening the Mars-van Krevelen (M-K), Langmuir-Hinshelwood (L-H), and Eley-Rideal (E-R) mechanisms.
查看更多>>摘要：? 2022 Elsevier B.V.In this work, we have investigated the electronic structure and electrical properties of sputter-deposited high-k dielectrics grown on p-GaAs substrate with post-deposition annealing at 500 °C/N2 ambient. Capacitance-voltage results show that co-sputtered amorphous-HfTiO2 alloy dielectric can reduce interfacial dangling bonds. HRTEM and AR- X-ray photoelectron spectroscopy results confirmed the formation of a thin interfacial layer during sputter deposition. At the atomistic level, the surface reaction and electronic interface structure were investigated by density-functional theory (DFT) calculations. Using the HSE functional, theoretical calculations of bulk HfO2, a-TiO2, and HfTiO2 band gaps are found to be 5.27, 2.61, and 4.03 eV, respectively. Consequently, in the HfTiO2/GaAs interface, the valance band offset is found to be reduced to 1.04 eV compared to HfO2/GaAs structure valance band offset of 1.45 eV. Reduction in border trap density (~1011 V/cm2) was observed due to Ti atoms bridging between As-dangling bonds. The angle-resolved XPS analysis further confirmed Ti-O-As chemical bonding with very thin (~20 ?) dielectric layers.
查看更多>>摘要：? 2022 Elsevier B.V.Currently, it is very necessary to find novel and practical anode materials for sodium ion batteries (SIBs) in energy research. Herein, utilizing the template of ZnS, hollow ZnS-Sb/C nanospheres were synthesized via a cation exchange reaction between Zn2+ and Sbx+ ions and annealing process. When applied as anode for SIBs, the ZnS-Sb/C nanospheres deliver an ultra-high reversible capacity of 747 mA h g?1 at 100 mA g?1 after 150 cycles, excellent cycling and rate performance. Additionally, the assembled Na3V2(PO4)3||ZnS-Sb/C full battery also exhibits good electrochemical performance. Combining the advantages of ZnS and metal Sb, the ZnS-Sb/C nanospheres can largely increase the battery capacity and maintain the phase stability, meanwhile hollow structure provides high specific surface area and carbon layer contributes stable support and excellent conductivity. All the rational design can synergistically provide buffer for the volume expansion during the Na+ intercalation/de-intercalation. Moreover, the high contribution of pseudocapacitance behavior contributes to the superior rate capability and long-term cycling stability. Therefore, ZnS-Sb/C nanospheres will provide a promising strategy for enhancing the performance of SIBs for practical industrialization.
查看更多>>摘要：? 2022 Elsevier B.V.This paper reported the correlations between electrocaloric effect (ECE) and dielectric diffuseness of Ba(Ti1-xSnx)O3 (abbreviated as BT-100xSn) ceramics. The BT-100xSn with pure perovskite structure has been synthesized by conventional solid-state reaction method. The temperature dependence of dielectric permittivity indicates that all the BT-100xSn ceramics are normal ferroelectric with diffused phase transition, and the dielectric diffuseness is strengthened as the Sn contents increase. The maximum ECE takes place in the vicinity of phase transition point, which is the characteristic of normal ferroelectrics. The BT-8Sn indicates the largest ?T = 0.46 K and ?T/?E = 0.30 × 10?6 K m/V. The substitutions of Sn contents adjust the maximum ECE to different temperatures, and the good temperature-modulation of ECE is beneficial for the realization of ECE application. Considering the correlations between ECE and dielectric diffuseness, the experimental results demonstrate that the stronger dielectric diffuseness leads to the strengthened temperature stabilities of ECE but accompanied with decreased maximum ECE.
查看更多>>摘要：? 2022 Elsevier B.V.Search for high-performance thermoelectric materials are attractive in directly conversion between heat and useful powers for relieving the energy crisis nowadays. SnTe alloy is always expected to be one ecofriendly candidate, however, its low conversion efficiency has severely limited the practical application as thermoelectric devices, mainly due to the intrinsic low power factor. Here we show that siginificantly enhanced power factors can be achieved in nano-polycrystalline SnTe doped with a small amount elemental Indium (In). Our results demonstrate that the fabricated SnTe in this work shows simultaneously enhanced Seebeck coefficient and decreased carrier concentration with the increase of In content up to 1.25 at%, leading to remarkably improvement of power factors by 95% at 300 K and 56% at 710 K for In0.01Sn0.99Te. Meanwhile, the introduced abundant grain boundaries, dislocations, and lattice distortion in the nanostructured SnTe, which are beneficial for the phonon scattering, can effectively reduce the phonon thermal conductivity. As a result, we observe significant improvement of the conversion efficiency for SnTe throughout wide temperature range from 300 to 710 K and the average ZT in In0.0125Sn0.9875Te can reach up to 0.34, the highest value reported in SnTe-based materials, paving a new way for promising high-performance thermoelectrics.
查看更多>>摘要：? 2022 Elsevier B.V.Improving the crystallinity of polymeric carbon nitride has been proved highly efficient for advanced photocatalysis. Nevertheless, controllable tuning the in-plane and interlayer crystallinity of crystalline carbon nitride has not been realized and their specific effect on photocatalysis is not clear yet. Herein, we proposed a facile one-step approach to selectively fabricate the in-plane or interlayer ordered crystalline carbon nitride by calcining melamine with KOH and NH4Cl at different KOH/NH4Cl ratios. Specifically, a high KOH/NH4Cl ratio results in sample with a highly in-plane integrity while a low ratio leads to a more orderly interlayer stacking. All the crystalline carbon nitride samples exhibit significantly boosted photocatalytic H2 evolution reaction rate as compared to polymeric carbon nitride, suggesting the positive contribution of enhanced crystallinity to photocatalytic activity. More importantly, the as-prepared sample with a highly in-plane integrity surpasses another sample with a more orderly interlayer stacking in photocatalytic performance, benefitting from its highly in-plane ordered structure, which extends light-harvesting range and promotes exciton dissociation. This work provides a platform to investigate the structure activity relationship between crystallinity and photocatalytic properties of crystalline carbon nitride.
查看更多>>摘要：? 2022Designed synthesis of robust while earth-abundant carbon-based electrocatalysts for oxygen reduction reaction (ORR) is central for the wide spread application of renewable energy conversion technologies. Herein, graphitized and curved carbon nanochambers decorated with boron and nitrogen tailored highly-dispersed cobalt moieties (B,N-Co/GCCN) were developed via a feasible strategy combining room temperature crosslinking and in situ catalytic graphitization processes. The graphitized and curved carbon nanochambers enhanced the electron transfer and structural stability and tailored the electronic structure of metal active sites. Moreover, the in situ coupled amorphous carbon and cobalt-nitrogen/boron moieties represented catalytically active sites for catalyzing ORR. Notably, the selected B doping made the electron density of Co of B,N-Co/GCCN higher compared to N-Co/GCCN, promoting the adsorption and activation of oxygen molecule. Benefiting from this integrated structure, the B,N-Co/GHC exhibited high ORR activity comparable to commercial Pt/C catalyst, along with robust electrocatalytic stability with little change in half-wave potential after 5000 cycles. Impressively, a homemade zinc-air battery driven by B,N-Co/GHC showed higher discharging performance than the one driven by Pt/C, demonstrating promising application prospect.
查看更多>>摘要：? 2022 Elsevier B.V.Currently, economic hydrogen production is the key issue preventing the application of the hydrogen as the energy carrier for global low-carbon and ever-increasing energy challenges. Hydrogen generation by spontaneous hydrolysis reaction of light metal-based materials including Mg, Al and NaBH4, is a promising method integrating safe storage and effective supply of hydrogen. However, these hydrolytic materials are still plagued by sluggish hydrogen kinetics and low H2 yield, owing to the formation of the surface passivation layers. While numerous strategies such as refining material's structure, compositing with other materials, alloying and modifying aqueous solutions, have been proposed to enhance hydrogen generation performance, the high cost caused by irreversibility hinders the large-scale application. Therefore, low cost regeneration of materials from hydrolytic byproduct is essential for hydrogen generation via hydrolysis. Herein, this review presents the recent research progress on above topics as well as their application in fuel cells. The future challenges and opportunities in this area are also described.
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