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.

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。

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。

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.

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.

微波辅助回流法制备桑椹形Na_3V_2(PO_4)_2O_2F@C正极材料用于高性能钠/锂离子电池（英文）

本论文采用快速微波辅助低温回流策略制备了桑椹形Na_3V_2(PO_4)_2O_2F@C纳米复合材料.研究表明微乳液中的V(acac)_3反胶束体系对该自组装结构的形成起到了关键作用.制得的Na_3V_2(PO_4)_2O_2F晶粒沿着[002]方向生长并被原位包封在碳壳中,形成了高度稳定的自组装结构,这不仅有利于Na^+/e^-的快速迁移,而且能够有效改善电极材料的循环性能并抑制电压衰减.作为钠离子电池正极材料,在0.1 C条件下, Na_3V_2(PO_4)_2O_2F@C的初始放电容量约为127.9 mA h g^(-1).在高倍率(20 C)条件下,容量达88.1 mA h g^(-1), 2000次循环后容量保持率为82.1%.此外,利用非原位X射线衍射, X射线光电子能谱和恒电流间歇滴定技术,初步研究了Na_3V_2(PO4)_2O_2F@C在充放电过程中的反应机理和Na^+迁移机制.同时,在Li/Na离子混合电池当中, Na_3V_2(PO_4)_2O_2F@C也表现出了优异的倍率和循环性能.上述微波辅助低温回流合成策略为开发高性能电化学储能材料开辟了新的途径.

聚酞菁铁驱动的三元平衡Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5作为氧还原反应高效催化剂

聚酞菁具有典型的化学交联结构和均匀分散的金属活性位点,但是较差的活性和导电性限制了其作为氧还原催化剂的应用.本文通过热解聚酞菁铁与多孔碳的混合物制备了三元氧还原催化剂,产物Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5在碱性溶液中的半波电势为0.90 V,远高于市售20%Pt/C的半波电势.电化学测试和X射线吸收精细结构相结合,将Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5的优异氧还原活性归因于Fe_(3)O_(4),Fe_(3)N和Fe-N4三种组分的共存.以Fe_(3)O_(4)/Fe_(3)N/FeN-C@PC-2.5作为空气阴极催化剂的锌空气电池具有较高的开路电压和峰值功率密度.在恒电流放电过程中,该电池的比容量可达到815.7 mA h g^(-1).

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.

具有协同电子结构和形貌调控功能的三元Co_(1-x)V_(x)P纳米针阵列在大电流下的析氢性能研究

制备具有大电流析氢性能的非贵金属电催化剂是一个巨大挑战.协同调控催化剂的电子结构和形貌能够增强其本征催化能力和增加活性位点,被认为是提高催化性能的有效方法.本文以具有协同电子结构和形貌调控功能的三元Co_(1-x)V_(x)P纳米针阵列作为碱性析氢的高效电催化剂.实验和理论计算结果表明,其优异的催化性能来源于物理化学性质的提高、活性表面积的增加及反应动力学的加速.此外,组装的(NF@Co_(1-x)V_(x)–HNNs(+)||NF@Co_(1-x)V_(x)P(-))电解池在1.58、1.75和1.92 V的电压下,能够分别得到10、100和300 mA cm^(-2)的电流密度.

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.