Enhancing Green Ammonia Electrosynthesis Through Tuning Sn Vacancies in Sn‑Based MXene/ MAX Hybrids

Renewable energy driven N_(2) electroreduction with air as nitrogen source holds great promise for realizing scalable green ammonia production.However,relevant out-lab research is still in its infancy.Herein,a novel Sn-based MXene/MAX hybrid with abundant Sn vacancies,Sn@Ti_(2)CTX/Ti_(2)SnC–V,was synthesized by controlled etching Sn@Ti_(2)SnC MAX phase and demonstrated as an efficient electrocatalyst for electrocatalytic N2 reduction.Due to the synergistic effect of MXene/MAX heterostructure,the existence of Sn vacancies and the highly dispersed Sn active sites,the obtained Sn@Ti2CTX/Ti_(2)SnC–V exhibits an optimal NH_(3) yield of 28.4μg h^(−1) mg_(cat)^(−1) with an excellent FE of 15.57% at−0.4 V versus reversible hydrogen electrode in 0.1 M Na_(2)SO_(4),as well as an ultra-long durability.Noticeably,this catalyst represents a satisfactory NH3 yield rate of 10.53μg h^(−1) mg^(−1) in the home-made simulation device,where commercial electrochemical photovoltaic cell was employed as power source,air and ultrapure water as feed stock.The as-proposed strategy represents great potential toward ammonia production in terms of financial cost according to the systematic technical economic analysis.This work is of significance for large-scale green ammonia production.

Self-derivation and reconstruction of silver nanoparticle reinforced cobalt-nickel bimetallic hydroxides through interface engineering for overall water splitting

Designing efficient and long-lasting non-metal electrocatalysts is an urgent task for addressing the issue of kinetic hysteresis in electrochemical oxidation reactions.The bimetallic hydroxides,catalyzing the oxygen evolution reaction(OER),have significant research potential because hydroxide reconstruction to generate an active phase is a remarkable advantage.Herein,the complete reconstruction of ultrathin CoNi(OH)_(2) nanosheets was achieved by embedding Ag nanoparticles into the hydroxide to induce a spontaneous redox reaction(SRR),forming heterojunction Ag@CoNi(OH)_(2) for bifunctional hydrolysis.Theoretical calculations and in situ Raman and ex situ characterizations revealed that the inductive effect of the Ag cation redistributed the charge to promote phase transformation to highly activate Ag-modified hydroxides.The Co-Ni dual sites in Co/NiOOH serve as novel active sites for optimizing the intermediates,thereby weakening the barrier formed by OOH^*.Ag@CoNi(OH)_(2) required a potential of 1.55 V to drive water splitting at a current density of 10 mA cm^(-2),with nearly 98.6% Faraday efficiency.Through ion induction and triggering of electron regulation in the OER via the synergistic action of the heterogeneous interface and surface reconstruction,this strategic design can overcome the limited capacity of bimetallic hydroxides and bridge the gap between the basic theory and industrialization of water decomposition.

花生芽中白藜芦醇的微波和超声波组合提取研究

本文采用微波和超声波组合法从花生芽中提取白藜芦醇浸膏,并以HPLC法测定所得到的浸膏中白藜芦醇含量。在恒定微波功率600 W和超声波功率1500 W基础上,通过L16 (43)正交试验,考察了乙醇浓度、作用时间和提取温度三个因素对提取效果的影响。优选花生芽在微波和超声波组合作用条件下的最佳提取工艺,并考察该提取法提取白藜芦醇的效果。研究结果表明,微波和超声波组合作用对于花生芽中提取白藜芦醇具有较高的效率。采用这种组合作用的提取方法,乙醇浓度为主要影响因素,然后是提取温度,最后是作用时间。最优的提取工艺是提取溶剂为40%乙醇、微波和超声波作用时间为3 min和提取温度为65℃。

Different responses of soil respiration and its components to nitrogen and phosphorus addition in a subtropical secondary forest

Background:Nitrogen(N)and phosphorus(P)deposition have largely affected soil respiration(Rs)in forest ecosystems.However,few studies have explored how N and P individually or in combination to influence Rs and its components(autotrophic respiration,Ra;heterotrophic respiration,Rh),especially in highly P-limited subtropical forests.To address this question,we conducted a field manipulation experiment with N and/or P addition in a 50-year-old subtropical secondary forest.Results:We found that N addition on average reduced Rs,Ra,and Rh by 15.2%,15%,and 11.7%,respectively during 2-year field study.P addition had an inconsistent effect on Ra,with Ra increasing by 50.5%in the first year but reducing by 26.6%in the second year.Moreover,P addition on average decreased Rh by 8.9%–30.9%and Rs by 6.7%–15.6%across 2 years.In contrast,N and P co-addition on average increased Rs,Ra,and Rh by 1.9%,7.9%,and 2.1%during the experimental period.Though Rs and Rh were significantly correlated with soil temperature,their temperature sensitivities were not significantly changed by fertilization.Ra was predominantly regulated by soil nitrogen availability(NH4+and NO3−),soil dissolved organic carbon(DOC),and enzyme activities,while the variation in Rh was mainly attributable to changes in soil microbial community composition and soilβ-D-Cellubiosidase(CB)andβ-Xylosidase(XYL)activities.Conclusion:Our findings highlight the contrasting responses of Rs and its components to N or P addition against N and P co-addition,which should be differentially considered in biogeochemical models in order to improve prediction of forest carbon dynamics in the context of N and P enrichment in terrestrial ecosystems.

Radiation-hardened property of single-walled carbon nanotube film-based field-effect transistors under low-energy proton irradiation

Strong C-C bonds,nanoscale cross-section and low atomic number make single-walled carbon nanotubes(SWCNTs)a potential candidate material for integrated circuits(ICs)applied in outer space.However,very little work combines the simulation calculations with the electrical measurements of SWCNT field-effect transistors(FETs),which limits further understanding on the mechanisms of radiation effects.Here,SWCNT film-based FETs were fabricated to explore the total ionizing dose(TID)and displacement damage effect on the electrical performance under low-energy proton irradiation with different fluences up to 1×1015 p/cm2.Large negative shift of the threshold voltage and obvious decrease of the on-state current verified the TID effect caused in the oxide layer.The stability of the subthreshold swing and the off-state current reveals that the displacement damage caused in the CNT layer is not serious,which proves that the CNT film is radiation-hardened.Specially,according to the simulation,we found the displacement damage caused by protons is different in the source/drain contact area and channel area,leading to varying degrees of change for the contact resistance and sheet resistance.Having analyzed the simulation results and electrical measurements,we explained the low-energy proton irradiation mechanism of the CNT FETs,which is essential for the construction of radiation-hardened CNT film-based ICs for aircrafts.

微波法提取分离肉桂醛

肉桂醛是一种重要的食品香料、医疗和保健药品以及化工原材料。常规的肉桂醛提取分离方法,主要采用索氏提取法和超声波提取法,分离主要采用水蒸气蒸馏法。本文采用微波提取法和微波水合物蒸馏分离法,从肉桂皮中提取分离肉桂醛。实验表明,本文所采用的微波方法不仅产率比较高,而且省时、高效和环保,具有重要的实践意义。

具有绿色降解自修复特性的苯氧树脂及其复合材料的制备

以苯硼酸(PBA)作为苯氧树脂(PO)的固化剂,采用一步法合成了一种含有可逆硼酸酯键(B—O—C)的新型苯氧树脂(POPBA30),并制备了碳纤维增强复合材料(CFRPs)。探讨了POPBA30树脂的固化过程和热性能,以及CFRPs的力学性能、热力学性能、降解性能、自修复性能及耐溶剂性能。利用红外光谱对PO、POPBA30、再生苯氧树脂(R-PO)和再生苯硼酸(R-PBA)进行了结构表征。通过差示扫描量热分析测得POPBA30的T_(g)高达206℃,热重分析测得POPBA30在空气和氮气气氛中的T_(d5)分别为411℃和399℃,800℃的质量保留率均高于38%;POPBA30还具有良好的耐化学性,可以在常见的溶剂中稳定存在21 d。以POPBA30为基体制备复合材料(CF/POPBA30),通过万能试验机测得其弯曲强度、层间剪切强度和抗张强度分别为975 MPa,55MPa和734 MPa。CF/POPBA30还具有优异的自修复性能,自修复效率约为85.6%。此外,CF/POPBA30可在室温下99%的乙醇水溶液中发生绿色降解,并实现对碳纤维和苯氧树脂的回收。

Nitrous oxide emissions from three temperate forest types in the Qinling Mountains,China

To understand soil N2O fluxes from temperate forests in a climate-sensitive transitional zone,N2O emissions from three temperate forest types(Pinus tabulaeformis,PTT;Pinus armandii,PAT;and Quercus aliena var.acuteserrata,QAT)were monitored using the static closed-chamber method from June 2013 to May 2015 in the Huoditang Forest region of the Qinling Mountains,China.The results showed that these three forest types acted as N2O sources,releasing a mean combined level of 1.35±0.56 kg N2O ha^-1 a^-1,ranging from0.98±0.37 kg N2O ha^-1 a^-1 in PAT to 1.67±0.41 kg N2O ha^-1 a^-1 in QAT.N2O emission fluctuated seasonally,with highest levels during the summer for all three forest types.N2O flux had a significantly positive correlation with soil temperature at a depth of 5 cm or in the water-filled pore space,where the correlation was stronger for temperature than for the water-filled pore space.N2O flux was positively correlated with available soil nitrogen in QAT and PAT.Our results indicate that N2O flux is mainly controlled by soil temperature in the temperate forest in the Qinling Mountains.

Copper-induced formation of heterostructured Co_(3)O_(4)/CuO hollow nanospheres towards greatly enhanced lithium storage performance

We report a facile template-free fabrication of heterostructured Co_(3)O_(4)/CuO hollow nanospheres using pre-synthesized Co/Cu-glycerate as conformal precursor.The introduction of copper nitrate in the solvothermal reaction system of glycerol/isopropanol/cobalt nitrate readily induces the conversion from solid Co-glycerate to hollow Co/Cu-glycerate nanospheres,and the effect of the Co/Cu atomic ratio on the structure evolution of the metal glycerates as well as their corresponding oxides were investigated.When examined as anode materials for lithium-ion batteries,the well-defined Co_(3)O_(4)/CuO hollow nanospheres with Co/Cu molar ratio of 2.0 demonstrate excellent lithium storage performance,delivering a high reversible capacity of 930 mAh/g after 300 cycles at a current density of 0.5 A/g and a stable capacity of 650 mAh/g after 500 cycles even at a higher current density of 2.0 A/g,which are much better than their counterparts of bare CuO and Co_(3)O_(4).The enhanced lithium storage performance can be attributed to the synergistic effect of the CuO and Co_(3)O_(4)heterostructure with hollow spherical morphology,which greatly enhances the charge/electrolyte transfer and effectively buffers the volume changes upon lithiation/delithiation cycling.

Fe regulating Ni_(3)S_(2)/ZrCoFe-LDH@NF heterojunction catalysts for overall water splitting

With the continuous depletion of traditional energy sources,the development of sustainable energy sources has become one of the important tasks today.A two-step synthesis method was employed to construct Ni_(3)S_(2)/ZrCoFe-LDH@NF heterostructured electrocatalysts on nickel foam(NF)in situ.X-ray diffractometer,scanning electron mi-croscope,transmission electron microscope,and X-ray electron spectroscopy were employed to characterize the Ni_(3)S_(2)/ZrCoFe-LDH@NF heterostructure,and the hydrogen-extraction reaction(HER),oxygen-extraction reaction(OER)and total hydrolysis properties of this electrocatalyst were tested in 1 mol·L^(-1)KOH electrolyte.It is shown that Ni_(3)S_(2)/ZrCoFe-LDH@NF is a lamellar stacked heterostructure with an overpotential of 330 mV and a Tafel slope of 90.9 mV·dec^(-1)at a current density of 100 mA·cm^(-2)in the OER reaction and 159.2 mV at a current density of 10 mA·cm^(-2)in the HER reaction.The Tafel slope is 96 mV·dec^(-1),and the catalyst exhibits good structural stability in the 100 h total hydrolysis stability test.The successful construction of this heterostructured electrocatalyst provides a good idea and research basis for the subsequent heterojunction and its application in electrocatalysis.

Rapid microwave-assisted refluxing synthesis of hierarchical mulberry-shaped Na_3V_2(PO_4)_2O_2F@C as high performance cathode for sodium & lithium-ion batteries

Unique hierarchical mulberry-shaped Na3V2(PO4)2O2F@C nanocomposite was fabricated by a rapid microwave-assisted low-temperature refluxing strategy. The V(acac)3 reverse micelle systems in the water-in-oil microemulsions played key roles in forming the self-assembly architectures. The prepared Na3V2(PO4)2O2F@C nanoparticles with the anisotropic growth along the [002] direction were in-situ encapsulated in carbon shells, which greatly contribute to fast Na+/e-transfer in electrodes. And the self-assemblies with high structure stability help to improve the cycle performance and mitigate voltage fading. The initial discharge capacity of Na3V2(PO4)2O2F@C as cathode for sodium ion batteries is about 127.9 m A h g-1 at 0.1 C. Besides, a high rate performance with a capacity of 88.1 mA h g-1 at 20 C has been achieved, and the capacity retains 82.1% after 2,000 cycles. In addition, the reaction kinetics and Na+ transportation mechanism of Na3V2(PO4)2O2F@C were preliminarily investigated by the ex situ X-ray diffraction, X-ray photoelectron spectroscopy and galvanostatic intermittent titration technique. More interestingly, when coupled with Li, the fabricated hybrid Li/Na-ion batteries also exhibit excellent rate and cycling performances. The proposed rapid refluxing strategy to synthesize mulberry-shaped Na3V2(PO4)2O2F@C opens up a new opportunity to develop high-performance electrode materials for the energy storage systems.

Synergistic electronic and morphological modulation on ternary Co_(1-x)V_(x)P nanoneedle arrays for hydrogen evolution reaction with large current density

It is a great challenge to prepare non-noble metal electrocatalysts toward hydrogen evolution reaction(HER)with large current density.Synergistic electronic and morphological structures of the catalyst have been considered as an effective method to improve the catalytic performance,due to the enhanced intrinsic activity and enlarged accessible active sites.Herein,we present novel ternary Co_(1-x)V_(x)P nanoneedle arrays with modulated electronic and morphological structures as an electrocatalyst for highly efficient HER in alkaline solution.The NF@Co1-xVxP catalyst shows a remarkable catalytic ability with low overpotentials of 46 and 226 mV at current densities of 10 and 400 mA cm^(-2),respectively,as well as a small Tafel slope and superior stability.Combining the experimental and computational study,the excellent catalytic performance was attributed to the improved physical and chemical properties(conductivity and surface activity),large active surface area,and fast reaction kinetics.Furthermore,the assembled Co–V based electrolyzer(NF@Co_(1-x)V_(x)–HNNs(+)||NF@Co_(1-x)V_(x)P(-))delivers small full-cell voltages of 1.58,1.75,and 1.92 V at 10,100,and 300 mA cm^(-2),respectively.Our findings provide a systematic understanding on the V–incorporation strategy to promote highly efficient ternary electrocatalysts via synergistic control of morphology and electronic structures.

Analysis and field test on reactive capability of photovoltaic power plants based on clusters of inverters

With the increasing capacity of photovoltaic(PV)power plants connected to power systems, PV plants are often required to have some reactive power control capabilities to participate in reactive power regulation. Reactive power regulation of grid-connected PV inverters can be achieved using different control strategies. In this paper, the reactive power capability of inverters and the technical requirement of PV plants are analyzed. The reactive power capability of a 30 MW PV plant is evaluated against relevant technical standards using a new testing method proposed in this paper.

Iron polyphthalocyanine-derived ternary-balanced Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 as a high-performance electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is the cornerstone reaction of the cathode in metal±air batteries;however,slow kinetics requires high-performance catalysts to promote the reaction.Polyphthalocyanine (PPc) has a typical chemical cross-linking structure and uniformly dispersed metal active sites,but its poor activity and conductivity limit its applications as an ORR catalyst.Herein,a manageable and convenient strategy is proposed to synthesize ternary ORR catalysts through the low-temperature pyrolysis of Fe PPc.The optimal catalyst,Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5,exhibits excellent ORR activity in alkaline solution with a half-wave potential of 0.90 V,which is significantly higher than that of commercial 20%Pt/C (0.84 V).Electrochemical tests and extended X-ray absorption fine structure spectroscopy reveal that the superior ORR activity of Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 could be ascribed to the balance of its ternary components(i.e.,Fe_(3)O_(4),Fe_(3)N,and Fe-N;species).A Zn±air battery incorporating Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 as an air cathodic catalyst delivers a high open-circuit voltage and peak power density.During galvanostatic discharge,the battery demonstrates a specific capacity of 815.7 mA h g^(-1).The facile strategy of using PPc to develop high-performance composite electrocatalysts may be expanded to develop new types of catalysts in the energy field.

Plasma transport simulation under different conditions and optimization analysis of dual-stage grid ion thruster

In order to study the extraction and acceleration mechanism of the dual-stage grid,a three-dimensional model based on the Particle-In-Cell/Monte Carlo Collision(PIC/MCC)method is performed.Dual-stage grid ion thruster is a new type of electrostatic ion thruster,which can break through the limitations of traditional gridded ion thrusters,and greatly improve the specific impulse.The high performance also makes the grid sensitive to operating parameters.In this paper,the influence of grid parameters on xenon ion thruster’s performance in a wide range is systematically simulated,and the optimal operating condition is given.Both the over-focusing of the plume,and the transparency of the screen grid are improved,and the grid corrosion is reduced through simulation optimization.The specific impulse under the given working conditions is 9877.24 s and the thrust is 7.28 mN.Based on the simulation optimization,the limitation of the dual-stage grid is discussed.The grid performs well under high voltage conditions(>3000 V)but not well under low voltage conditions(<2000 V).Finally,since argon is cheaper and more advantageous in future engineering applications,the plasma distribution and grid extraction ability under xenon and argon are analyzed and compared to study the flexibility of the dual-stage grid ion thruster.The simulation results show that a set of optimal parameters is only applicable to the corresponding propellant,which needs to be optimized for different propellant types.

Time-course of perceptual processing of “hole” and “no-hole”figures: An ERP study

Closure or the presence of a ＂hole＂ is an emergent perceptual feature that can be extracted by the visual system early on. This feature has been shown to have perceptual advantages over openness or ＂no-hole＂. in this study, we investigated when and how the human brain differentiates between ＂hole＂ and ＂no-hole＂ figures. Event-related potentials （ERPs） were recorded during a passive observation paradigm. Two pairs of simple figures （Experiment 1） and two sets of Greek letters （Experiment 2） were used as stimuli. The ERPs of ＂hole＂ and ＂no-hole＂ figures differed ~90 ms after stimulus onset： ＂hole＂ figures elicited smaller P1 and N1 amplitudes than ＂no-hole＂ figures. These suggest that both P1 and N1 components are sensitive to the difference between ＂hole＂ and ＂no-hole＂ figures; perception of ＂hole＂ and ＂no-hole＂ figures might be differentiated early during visual processing.