Hydroxide exchange membrane (HEM) water electrolysis is promising for green hydrogen production due to its low cost and excellent performance. However, HEM often has insufficient stability in strong alkaline solutions, particularly under in-situ electrolysis operation conditions, hindering its commercialization. In this study, we discover that the in-situ stability of HEM is primarily impaired by the locally accumulated heat in HEM due to its low thermal conductivity. Accordingly, we propose highly thermally conductive HEMs with an efficient three-dimensional (3D) thermal diffusion network to promote the in-situ stability of HEM for water electrolysis. Based on the 3D heat conductive network, the thermal conductivity of polymeric HEM is boosted by 32 times and thereby reduce the HEM temperature by up to 4.9 °C in a water electrolyzer at the current density of 1 A cm−2. Thus, the thermally conductive HEM exhibits negligible degradation after 20,000 start/stop cycles and reduces the degradation rate by 6 times compared to the pure polymeric HEM in a water electrolyzer. This study manifests the significance of thermal conductivity of HEM on the durability of water electrolysis, which provides guidelines on the rational design of highly durable HEMs in practical operation conditions for water electrolysis, fuel cells, and beyond. Hydroxide exchange membranes are desirable for water electrolysis but are limited by their instability under operational conditions. Here, authors find that the in-situ stability of the membranes is affected by the locally accumulated heat and can be enhanced by thermally conductive membranes.

We develop a self-consistent one-dimensional model based on plasma fluid theory and the drift-diffusion approximation to investigate how the discharge characteristics, as well as the symmetry, in atmospheric argon RF DBD, are affected when there are differences in the dielectric thickness. The simulation results show that as the dielectric thickness increases, the produced plasma density decreases. The thicker dielectric hinders the ionization process, leading to a significant decrease in the overall ionization rate and electron power absorption of the discharge and a change in their distribution, which characterizes the transition of the discharge from the alpha-gamma mode to the alpha-mode. Moreover, the asymmetric dielectric thickness allows the variation of the electric field to accrue to the thinner side of the dielectric thickness, which in turn deflects the distribution of the plasma towards this side. Also, it behaves as an alpha-gamma mode on the thinner side of the dielectric and an alpha-mode on the other side, resulting in different discharge modes occurring simultaneously on both sides of the same discharge gap. The asymmetric effect of the dielectric thickness on the energy produced is more evident in electron pressure heating and less in electron Ohmic heating.

In this work, based on plasma fluid theory, a 1D model of plasma in atmospheric argon RF dielectric barrier discharge with the assumption of drift-diffusion approximation is established to investigate the effect of secondary electron emission on the discharge characteristics. From the momentum equation of electrons, a detailed decomposition of electron heating is divided into electron pressure heating and electron Ohmic heating. The numerical results indicate that the higher the secondary electron emission coefficient, the higher the plasma density generated by the discharge. The electron temperature is less responsive to changes in secondary electron emission. Moreover, with the secondary electron emission coefficient increasing from 0 to 0.2, the discharge is fully transformed from the alpha-mode to the gamma-mode, which is judged by the conversion of the location of the onset of the ionization from the outer side of the expanding sheaths to the inner side of the sheaths. In addition, when the secondary electron emission is ignored, the electron pressure heating actually represents a cooling process. As the secondary electron coefficient increases, the electron density gradient in the vicinity of the sheaths is reversed, and the electron pressure heating here begins to turn positive. Electron Ohmic heating is the dominant heating mechanism.

Due to its dynamic and non-invasive characteristics, it is difficult to obtain stable and accurate measurement results using contact thermocouple temperature measurement. The temperature measurement accuracy of infrared thermal imaging cameras in non-invasive temperature measurement is affected by factors such as flame emissivity and radiation path attenuation, and there is also a large temperature measurement error. Among them, the colorimetric thermometer can avoid the influence of the emissivity of the measured target, and has the advantages of high accuracy, strong anti-interference ability, and wide temperature measurement range. However, in engineering use, due to the energy zero points set by long-wave and short-wave radiation, the data calculated and output based on the principle of colorimetric thermometry has a "temperature breakpoint" phenomenon. Based on this kind of engineering situation, this paper proposes a temperature calibration method for colorimetric thermometers and a temperature data breakpoint repair method. The actual measurement and verification experiment of a high-temperature blackbody furnace has proven the effectiveness of this temperature data breakpoint repair method, providing more accurate temperature data values for experiments such as flame temperature testing.

Design and working principle of bacterial capture and identification using a ZnO/Ag microfluidic SERS sensor array.

A core-shell-shell sandwich material is developed with silver nanowires as the core, ZIF-8 as an inner shell, and gold nanoparticles as the outer shell, namely, Ag@ZIF-8@Au nanowires (AZA-NW). Then, the synthesized AZA-NW is transformed into a surface-enhanced Raman spectroscopy (SERS) sensor (named M-AZA) by the vacuum filtration method and used to enrich, detect, and inactivate traces of bacteria in the environment. The M-AZA sensor has three main functions: (1) trace bacteria are effectively enriched, with an enrichment efficiency of 91.4%; (2) ultrasensitive detection of trace bacteria is realized, with a minimum detectable concentration of 1 × 101 CFU/mL; (3) bacteria are effectively killed up to 92.4%. The shell thickness of ZIF-8 (5-75 nm) is controlled by adjusting the synthesis conditions. At an optimum shell thickness of 15 nm, the effect of gold nanoparticles and ZIF-8 shell on the sensor's stability, SERS activity, and antibacterial performance is investigated. The simulation of the SERS sensor using the finite difference time domain (FDTD) method is consistent with the experimental results, theoretically demonstrating the role of the gold nanoparticles and the ZIF-8 shell. The sensor also shows excellent stability, safety, and generalizability. The campus water sample is then tested on-site by the M-AZA SERS sensor, indicating its potential for practical applications.

Iron-cobalt alloy is a potential and economical magnetostrictive material, however, our microscopic understanding of the co-electrodeposition process of Fe-Co alloys is still unsatisfactory. In this work, a flat Fe-Co film with 10 & mu;m was successfully prepared by electrodeposition with a non-toxic sulfate solution. The effects of (NH4)2SO4, an important additive, were studied and DFT calculation was used to analyze the mechanism of (NH4)2SO4. EIS shows that (NH4)2SO4 can promote the Fe-Co co-deposition process and obviously inhibits the hydrogen evolution reaction. In addition, (NH4)2SO4 can significantly reduce the internal stress of the Fe-Co film by 110,000 MPa, so that the cracks caused by the internal stress are obviously removed. The results of quantum chemistry calculation further show that NH4+ is more inclined to adsorb on Fe-Co surface than H2O and H+, which reduces the hydrogen evolution on the electrode surface. The results are beneficial to improve the Fe-Co codeposition process, reduce the internal stress and to prepare a high-performance Fe-Co magnetic film. The films will be assembled on the electronic devices with sensors.

In this paper, a quad-stable piezoelectric vibration energy harvester induced by the geometric nonlinearity of springs is designed and investigated. The novelty is that by replacing the permanent magnets with a combination of springs, the system can be effectively protected from electromagnetic interference in the working environment. The innovative design of three hinged springs attached to the tip of the cantilever beam makes the stiffness of the structure inherently nonlinear, which can induce the multi-stability of the system. The Euler-Lagrange equations are applied to establish the governing equation of the energy harvester. The static bifurcation analysis reveals the evolution process of multi-stability. The complex dynamic frequency (CDF) method, an efficient approach to solving strongly nonlinear dynamic problems with multi-well systems, is then applied to deduce the system's amplitude-frequency response. Combinations of theoretical and numerical results show that among a wide frequency bandwidth, the system can exhibit such as single-, double- and quadruple-well periodic motions. Finally, experiments are set up to verify the advantage of inter-well motion on harvesting power. Result shows that geometric nonlinearity can effectively make the energy harvester exhibit multi-stability, generate different movement patterns, and obtain high harvesting power.

In this work, a novel method for preparation of SiC/SiO2 nanochain heterojunctions from sustainable agricultural wastes is reported. With corn stover and rice husk ash acting as carbon and silicon sources respectively, SiC/SiO2 nanochains consisting of beads 225 nm in diameter connected by strings 70 nm in diameter and overall 10 μm in length were prepared via a facile catalyst-free carbothermal reduction method. SiC/SiO2 nanochains with good yields and desirable morphologies were obtained at the optimum reaction temperature of 1500 °C and silicon to carbon source weight ratio of 1:3. A possible formation mechanism for the nanochains is proposed. In addition, compared with SiC nanowires, the photoluminescence (PL) spectra measured of the as-prepared SiC/SiO2 nanochains exhibited an obvious blue shift, which suggested that the nanochains have promising application prospects in the field of optical devices. This study provides a facile and environmentally friendly method for the production of SiC/SiO2 nanochain heterojunctions from common agricultural waste and promotes the principles of sustainable development.

In this work, p-type Bi0.5Sb1.5Te3 nanopowders with nanoflower morphology were successfully synthesized by a hydrothermal method. The nanopowders were then hot-pressed into bulk, and the thermoelectric properties of the pellets were examined. For comparison, Bi0.5Sb1.5Te3 nanopowders with nanoplate morphology and binary Bi2Te3/Sb2Te3 (0.5:1.5) nanocomposites were also prepared. The results showed that for the bulk made by nanopowders with nanoflower morphology, the microstructure consisted of tiny grains embedded in large particles. The larger grains in the bulk increased the electrical conductivity, and the energy filtering effect induced by the tiny grains increased the Seebeck coefficients, so the power factor of the Bi0.5Sb1.5Te3 samples made by nanoflowers was higher than that of the other samples. Meanwhile, the thermal conductivity of the Bi0.5Sb1.5Te3 samples made by nanoflowers was lower than that of the other samples due to the larger number of grain boundaries in the bulk. As a result, the ZT value of the bulk made by the Bi0.5Sb1.5Te3 samples with nanoflower morphology was higher than that of the other two samples for all testing temperatures. Here we provide a relatively simple synthesis route to produce bulk materials with reasonable microstructures to effectively improve the ZT.

To improve operational safety and system reliability, real-time wireless health monitoring systems are necessary for freight trains. However, due to the lack of onboard power and space restrictions, monitoring sensors rely on batteries as power sources, which are not eco-friendly and involve high maintenance costs for battery replacement. Therefore, developing self-powered maintenance-free wireless monitoring sensors integrated with energy harvesting is in urgent demand. Here, we propose a compact ultralow-frequency and broadband piezoelectric energy harvester (UBPEH) that can be easily installed in the limited space of the axle box to effectively harvest bogie lateral vibrations. The T-shaped UBPEH employs magnetic interaction to soften the stiffness and strengthen the stopper operation in a low-frequency range. To predict and optimize the prototype, we establish the model of UBPEH by considering the displacement, inclination angle, and shape of the magnets. Theoretical and experimental results show that the prototyped UBPEH might operate in the range of 1-11 Hz, covering the representative frequencies of bogie vibrations on freight trains. An output power of 605 kiW on a matched resistance of 200 k Omega under the acceleration of 11 Hz and 0.5 g (g = 9.8 m s(-2)) is achieved, and the harvested electric power can successfully drive typical commercial wireless Bluetooth sensors. Furthermore, the harvester possesses output stability and mechanical durability under actual service hours of freight trains. The results of this work pave the way to implement self-powered wireless condition monitoring on freight trains.

In situ polymerization has been used to prepare polypyrrole (PPy) supported reduced graphene oxide (RGO). The prepared PPy/RGO composites were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and X-ray photoelectron spectroscopy. The thermoelectric properties of the PPy/RGO composites were studied by measuring the Seebeck coefficient, electrical conductivity and power factor. The influences of the PPy/RGO composition and acids on the thermoelectric properties were also investigated. The results show that the thermoelectric properties of PPy/RGO composites prepared by in situ polymerization are better than those of PPy/RGO blends, and the thermoelectric properties increase as RGO content increases to 40% because of the increased carrier mobility. PPy/RGO composites doped with organic acids display superior thermoelectric properties to those doped with inorganic acids.

Investigation of Cu(II) and Se(IV) electrochemical reduction processes in solutions with poly(ethylene glycol) (PEG) provides important theoretical guidance for the preparation of Cu-Se alloy films with stronger thermoelectric properties. The results reveal that PEG adsorbing on the electrode surface does not affect the electrochemical reduction mechanism of Cu(II), Se(IV), and Cu(II)-Se(IV), but inhibits the electrochemical reduction rates. The surface morphology and composition change with a negative shift in the deposition potentials. The Cu-Se alloy film, which was prepared at 0.04 V, was α-Cu2Se as-deposited and P-type thermoelectric material after annealing. The highest thermoelectric properties were as follows: Seebeck coefficient (α) was +106 μV·K−1 and 1.89 times of Cu-Se alloy film electrodeposited in Cu(II)-Se(IV) binary solution without PEG; resistivity (ρ) was 2.12 × 10−3 Ω·cm, and the calculated power factor (PF) was 5.3 μW·cm−1K−2 and 4.07 times that without PEG.

In this paper, the preparation of Cu-doped BixCuySb2-x-yTez thin film thermoelectric materials by electrodeposition in inorganic solution system was studied. The effects of Cu2+ concentration on the properties of BixCuySb2-x-yTez thin film thermoelectric materials were investigated. The composition, morphology and phase of the prepared BixCuySb2-x-yTez thin films were characterized by energy dispersive spectroscopy, environmental scanning electron microscope and X-ray diffraction. The conductivity and Seebeck coefficient of BixCuySb2-x-yTez thin film prepared under different conditions were also tested. The results show that doping of Cu element into BixSb2-xTez thermoelectric material can not only reduce the resistivity of the material, but also improve the morphology of the material, and the Seebeck coefficient of BixCuySb2-x-yTez thermoelectric material can reach up to 152 μV/K. When the Cu2+ concentration is 1.28 mmol L-1, the highest power factor of 577.6μW∙K-2∙m-1 can be obtained.

金属、氮共掺杂碳材料类催化剂(Metal-N-C,Metal=Fe、Mn、Co等)具有良好的氧还原(ORR)催化性能,成为近年应用于燃料电池正极的非铂类催化剂的研究热点.普遍上,Fe-N-C类催化剂具有最高的ORR催化性能,但其促进的Fenton反应(Fe2++H2O2,ORR双电子过程的副产物)会导致PEMFC结构损坏.因此,使用酞菁锰(MnPc)为前驱体,通过有机金属气相沉积工艺,合成了一种以单层石墨烯为基体的Mn-N-C类催化剂(Mn-N-C/G-30).通过热重分析可知,MnPc分子在480℃下脱H形成悬空键而产生的分子间键合作用使其生长为Mn-N-C/G-30催化剂.通过SEM、TEM、XRD的形貌表征,表明合成Mn-N-C/G-30催化剂结构与前驱体酞菁锰完全不同,是一种新型叶片状纳米材料,且具单晶结构,其晶格间距为0.315 nm.通过Raman和XPS的结构表征,证明合成Mn-N-C/G-30催化剂结构中形成了不同于MnPc中Mn-N4配位结构的Mn-N活性位点.采用了三电极体系进行电化学测试.线性伏安扫描测试结果表明,合成Mn-N-C/G-30催化剂在25℃、0.1 mol/L的KOH水溶液中的ORR起始电位和在电位0.88 V条件下的电流密度分别为0.97 V和1.4 mA/cm2,优于MnPc(0.85 V和0.1 mA/cm2)和商业化Pt/C催化剂(0.94 V和1.3 mA/cm2)的性能(以上电位均相对于氢标电位).K-L图的计算结果表明,合成Mn-N-C/G-30催化剂上的ORR过程为高效的四电子转移步骤.

Fe基软磁材料主要有FeNi合金、FeCo合金和FeSi合金等.由于它们具备高磁化强度、高磁化率和低矫顽力等优异的软磁性能,而被广泛应用于电子、电气、国防等领域.随着科技的发展,要求电子元器件具有更小的尺寸和更优异的性能,因而对软磁性材料薄膜化的需求也日益迫切.从电化学基本原理出发,针对当前的研究现状,对电沉积合成Fe基软磁性薄膜材料的各个工艺参数的影响与调控进行了简单的分析与介绍.主要介绍了电沉积方法,并介绍了电沉积法多种调控沉积层成分、形貌、厚度以及性能的手段.随后介绍了Fe基软磁性薄膜的电沉积工艺研究现状,研究表明,沉积电流、镀液组成、镀液pH值、温度、沉积时间、外加磁场等因素均会影响磁性薄膜的组成及性能.此外,单独介绍了FeSi合金电化学制备复合电沉积技术,主要介绍了FeSi合金复合共沉积中硅的分散性问题,并对铁硅合金的电沉积研究现状作了简单总结.主要的目的在于能对当前Fe基软磁性材料的研究现状有一定的掌握,并对以后的发展使用提供借鉴.

Biomass-derived nitrogen-self-doped carbon was prepared by a simple and green approach based on the direct pyrolysis of pork heart using KOH as an activation reagent at controlled temperatures (700-900 degrees C). The obtained samples displayed a specific surface area up to 1718.84 m(2) g(-1), high content of nitrogen (3.03%) and interconnected porous structure, which is able to expose abundant active sites and promote mass transfer. Electrochemical measurements showed that our catalyst possessed a high electrocatalytic activity for oxygen reduction reaction in alkaline solution that is equivalent to that of commercial Pt/C. The sample carbonized at 700 degrees C (PC-APHs-700) with the onset potential of 0.92 V and half-wave potential of 0.80 V possessed the highest concentrations of graphite and pyridine nitrogen and exhibited the best performance among the PC-APHs-T samples. In addition, PC-APHs-700 had a higher long-term stability and stronger methanol tolerance than commercial Pt/C. This work demonstrates that it is a promising approach to develop and utilize carbon materials with added value as effective metal-free cathode catalysts for alkaline fuel cells based on economic and environmental friendly renewable biomass. (C) 2020 Elsevier Inc. All rights reserved.

Spinel-type manganese-cobalt oxides have been regarded as important class of electrocatalysts for oxygen reduction reaction (ORR). However, they are usually synthesized through oxidation-precipitation under aqueous ammonia and then crystallization at high temperature (150-180 degrees C), which not only increases the energy consumption but also induces the growth of particles that is unfavorable for ORR. Herein, through a facile precipitation-dehydration method, ultrasmall spinel manganese-cobalt oxide nanoparticles (similar to 5 nm) homogeneously dispersed on conductive carbon black (MnxCo3-xO4/C) were fabricated at low temperature (60 degrees C). And the bimetallic composite oxide (Mn1.5Co1.5O4/C) with cubic spinel structure and high Mn content exhibits remarkable enhancement of ORR activity and stability compared with single metal oxide (both Mn3O4/C and Co3O4/C). The essential reason for the enhancement of activity can be attributed to the presence of the mixed Mn3+ and Mn4+ cations in Mn1.5Co1.5O4/C. Moreover, the ORR activity of Mn1.5Co1.5O4/C is comparable to that of commercial 20 wt% Pt/C, and the relative current density only decreases 1.4% after 12 h test, exceeding that of Pt/C and most reported manganese-cobalt oxide electrocatalysts. (C) 2020, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

The electrochemical reduction of Bi(III), Sb(III) and Te(IV) with EDTA and tartaric acid complexing agents in sulfuric acid solution were studied by linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) separately. The results reveal that the addition of EDTA makes the reduction potential of Bi(III) shift negatively, but does not affect the reduction potential of Sb(III) and Te(IV), which makes the deposition potential of Bi(III), Sb(III) and Te(IV) close to each other. The addition of tartaric acid makes the reduction potential of Bi(III) negatively shift a little and the reduction potential of Sb(III) shift negatively, but does not affect the reduction potential of Te(IV), which makes the deposition potential of Bi(III), Sb(III) and Te(IV) far away from each other. Meanwhile, the role of EDTA is to increase the solubility of Bi(III), and tartaric acid is expected to improve the solubility of Sb(III), EDTA and tartaric acid could enhance the stability of Bi(III)-Sb(III)-Te(IV) ternary mixture. (C) 2019 The Electrochemical Society.

A single-atom TM-Nx (TM = Fe, Co, Mn, etc.) embedded graphene matrix is known for its excellent activity and durability in oxygen reduction reaction (ORR) catalysis. Among them, Mn-N4 sites have been theoretically proved to undergo a complete 4-electron pathway with low ORR overpotentials and low activation barriers in O2 dissociation. However, in reality there still remain significant activity gaps between such Mn-N4 based catalysts (such as MnPc and MnP) and Fe-N4 or Pt-group metal catalysts. The inferior ORR performance of MnPc and MnP could be attributed to the strong binding ability of Mn that causes great difficulties in removing the ORR products from the surface sites. On this basis, 17 types of Mn-Nx models containing various three-, four- and five-coordination groups were established. Systematic density functional theory (DFT) calculations were performed to investigate the N,C coordination effects on their corresponding ORR activities. Scaling relations were found among the binding strengths of key ORR intermediates, which could be modulated by the N doping level among different coordination groups. A volcano plot for ORR overpotentials (ηSHE) as a function of *OH adsorption free energy (ΔG*OH) was further established. The 3D five-coordination sites exhibit much higher ORR activity due to the great decrease in strong binding abilities compared with 2D three- or four-coordination sites. Particularly, (Cyan)Mn-N4/D is positioned near the apex of the volcano plot with an ηSHE of 0.33 V even lower than that of Pt(111) (0.34 V). Furthermore, the electron withdrawing/donating mechanisms among Mn, N, C, and O were investigated and related to the binding abilities of different coordination groups. Electronic structure calculations indicate that the binding abilities of Mn-Nx well correlate with the σ-type anti-bonding components between Mn-3d and O-2p states near the Fermi energy level.