Coupling ferromagnetic ordering electron transfer channels and surface reconstructed active species for spintronic electrocatalysis of water oxidation

Sluggish reaction kinetics of oxygen evolution reaction(OER), resulting from multistep proton-coupled electron transfer and spin constriction, limits overall efficiency for most reported catalysts. Herein, using modeled ZnFe_(2-x)Ni_xO_(4)(0 ≤ x ≤ 0.4) spinel oxides, we aim to develop better OER electrocatalyst through combining the construction of ferromagnetic(FM) ordering channels and generation of highly active reconstructed species. The number of symmetry-breaking Fe–O–Ni structure links to the formation of FM ordering electron transfer channels. Meanwhile, as the number of Ni^(3+)increases, more ligand holes are formed, beneficial for redirecting surface reconstruction. The electro-activated ZnFe_(1.6)Ni_(0.4)O_(4) shows the highest specific activity, which is 13 and 2.5 times higher than that of ZnFe_(2)O_(4) and unactivated ZnFe_(1.6)Ni_(0.4)O_(4), and even superior to the benchmark IrO_(2) under the overpotential of 350 mV. Applying external magnetic field can make electron spin more aligned, and the activity can be further improved to 39 times of ZnFe_(2)O_(4). We propose that intriguing FM exchange-field interaction at FM/paramagnetic interfaces can penetrate FM ordering channels into reconstructed oxyhydroxide layers, thereby activating oxyhydroxide layers as spin-filter to accelerate spin-selective electron transfer. This work provides a new guideline to develop highly efficient spintronic catalysts for water oxidation and other spin-forbidden reactions.

Surface Oxygen Injection in Tin Disulfide Nanosheets for Efficient CO_(2) Electroreduction to Formate and Syngas

Surface chemistry modification represents a promising strategy to tailor the adsorption and activation of reaction intermediates for enhancing activity.Herein,we designed a surface oxygen-injection strategy to tune the electronic structure of SnS_(2) nanosheets,which showed effectively enhanced electrocatalytic activity and selectivity of CO_(2) reduction to formate and syngas(CO and H_(2)).The oxygen-injection SnS_(2) nanosheets exhibit a remarkable Faradaic efficiency of 91.6%for carbonaceous products with a current density of 24.1 mA cm^(−2) at−0.9 V vs RHE,including 83.2%for formate production and 16.5%for syngas with the CO/H_(2) ratio of 1:1.By operando X-ray absorption spectroscopy,we unravel the in situ surface oxygen doping into the matrix during reaction,thereby optimizing the Sn local electronic states.Operando synchrotron radiation infrared spectroscopy along with theoretical calculations further reveals that the surface oxygen doping facilitated the CO_(2) activation and enhanced the affinity for HCOO*species.This result demonstrates the potential strategy of surface oxygen injection for the rational design of advanced catalysts for CO_(2) electroreduction.

Recent Advances in the Comprehension and Regulation of Lattice Oxygen Oxidation Mechanism in Oxygen Evolution Reaction

Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution reaction(OER)is a critical step in water electrolysis and is often limited by its slow kinetics.Two main mechanisms,namely the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM),are commonly considered in the context of OER.However,designing efficient catalysts based on either the AEM or the LOM remains a topic of debate,and there is no consensus on whether activity and stability are directly related to a certain mechanism.Considering the above,we discuss the characteristics,advantages,and disadvantages of AEM and LOM.Additionally,we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future.For instance,it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM.Furthermore,we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte(OH^(-)or H_(2)O).Additionally,we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.

Regional Economic Development in the Chinese Mode

The integrated development of central city is an important driving force for the boo-ming economy of a region. In paper, I study the level of development of the 35 central cit-ies and the?surrounding areas in China. With the factor analysis?model, I selecting 12 signific-ance indicators and using the SPSS 13.0 to make a rank for the 35 central cities’ develop-ment standard. Besides, making an analysis and giving some suggestions base on Chinese actual economic policies and regional realities.

深度学习揭示史上最大灭绝事件中生物形态演变过程

生物形态多样性(morphological diversity or disparity)是古生物学和现代生物学研究的核心内容之一,早在居维叶时期就曾将生物形状和结构的不连续性作为将动物分组的基础.生物形态多样性是定量化类群样本形态差异性的最直观方法之一,从而为化石类群的演化、繁盛和消亡提供了记录和解释.

Foraminiferal Extinction and Size Reduction during the Permian-Triassic Transition in Southern Tibet

The miniaturization of organisms during the Permian-Triassic mass extinction,as an ecological strategy in response to environmental devastation,has been widely recognized in diverse marine invertebrates.Previous studies on the extinction process and miniaturization of foraminifers in the Permian-Triassic interval have relied on the fossil record of the low-latitude Paleotethys or a global database,although data and materials from the high-latitude Neotethys region are still rare.To reveal the evolutionary patterns and spatial variability of foraminifers at different latitudes and paleogeographic contexts,here we investigated the fossil distribution and size variation of foraminifers in the Selong Section of southern Tibet,located in the mid-latitude Neotethys of the Southern Hemisphere during the Permian-Triassic transition.The results show that the foraminifer of the Selong Section experienced a two-pulsed extinction(total species extinction rate of 71%),consistent with the time in South China but with a lower magnitude of extinction.Meanwhile,the data show that foraminiferal test volume was significantly miniaturized following the first pulse of extinction event:the mean size of post-extinction foraminifer was only 15%of that in the pre-extinction,mainly reflected by the disappearance of large forms as well as occurrences of smaller survivors and originators.Combined with the South China record,size data from southern Tibet indicate that the miniaturization of foraminifera is synchronous in the Paleotethys and Neotethys but smaller in magnitude in the Neotethys.We propose that ocean anoxia and acidification may be the environmental pressures leading to local and global foraminiferal miniaturizations,along with global warming,which might play a dominant role.

An Improved Modulation Strategy for Single-phase Three-level Neutral-point-clamped Converter in Critical Conduction Mode

Two-level totem-pole power factor correction(PFC)converters in critical conduction mode(CRM)suffer from the wide regulation range of switching frequency.Besides,in highfrequency applications,the number of switching times increases,resulting in significant switching losses.To solve these issues,this paper proposes an improved modulation strategy for the single-phase three-level neutral-point-clamped(NPC)converter in CRM with PFC.By optimizing the discharging strategy and switching state sequence,the switching frequency and its variation range have been efficiently reduced.The detailed performance analysis is also presented regarding the switching frequency,the average switching times,and the effect of voltage gain.A 2 k W prototype is built to verify the effectiveness of the proposed modulation strategy and analysis results.Compared with the totem-pole PFC converter,the switching frequency regulation range of the three-level PFC converter is reduced by 36.48%and the average switching times is reduced by 45.10%.The experimental result also shows a 1.2%higher efficiency for the three-level PFC converter in the full load range.

Regulating atomic Fe-Rh site distance for efficient oxygen reduction reaction

Exploring the atomic interaction mechanisms of dense single-atom catalysts(SACs)is of great significance for their application in oxygen reduction reaction(ORR).However,the intrinsic mechanism of the site-distance effect on the catalytic performance has been largely ignored.Here,we demonstrate the site-distance effect of Fe-Rh_(x)@NC catalysts in ORR theoretically and experimentally.Bader charge analysis reveals that the strong interaction between Fe and Rh atoms at a certain atomic distance(dFe-Rh)alters the catalytic electronic structure,facilitating the optimization of catalyst adsorption strength.Motivated by the theoretical calculations,we designed and synthesized the Fe-Rhx@NC catalysts through a spatial confinement strategy.The characterization results prove that the Fe-Rh_(2)@NC has the optimal d_(Fe-Rh),which improves its intrinsic ORR activity,providing a half wave potential of 0.91 V,higher than that of the commercial Pt/C(0.86 V).This study emphasizes the importance of determining the basic mechanism of the site-distance effect in dissimilar metal atoms catalysts,which is conducive to the design of efficient catalyst systems for practical applications.

Design of bifunctional single-atom catalysts NiSA/ZIF-300 for CO_(2) conversion by ligand regulation strategy

Carbon-supported noble-metal-free single-atom catalysts(SACs)have aroused widespread interest due to their green chemistry aspects and excellent performances.Herein,we propose a“ligand regulation strategy”and achieve the successful fabrication of bifunctional SAC/MOF(MOF=metal-organic framework)nanocomposite(abbreviated NiSA/ZIF-300;ZIF=ZIF-8)with exceptional catalytic performance and robustness.The designed NiSA/ZIF-300 has a planar interfacial structure with the Ni atom,involving one S and three N atoms bonded to Ni(Ⅱ),fabricated by controllable pyrolysis of volatile Ni-S fragments.For CO_(2) cycloaddition to styrene epoxide,NiSA/ZIF-300 exhibits ultrahigh activity(turnover number(TON)=1.18×105;turnover frequency(TOF)=9830 molSC·mol_(Ni)^(-1)·h^(-1);SC=styrene carbonate)and durability at 70℃ under 1 atm CO_(2) pressure,which is much superior to Ni complex/ZIF,NiNP/ZIF-300,and most reported catalysts.This study offers a simple method of bifunctional SAC/MOF nanocomposite fabrication and usage,and provides guidance for the precise design of additional original SACs with unique catalytic properties.

Atomically precise Ru-O-Ru clusters for enhanced water dissociation in alkaline hydrogen evolution

Atomic clusters typically exhibit distinctive electronic structures and physicochemical properties.However,as the size decreases,their ability to adsorb and dissociate water also diminishes,thereby affecting chemical reactions involving water molecules.Enhancing the adsorption and dissociation capabilities of atomic clusters towards water molecules and elucidating the mechanisms underlying their performance enhancement have become important research directions.Herein,employing the carrier-anchored strategy,Ru-O-Ru atomic clusters were prepared and displayed excellent activity and durability in the hydrogen evolution reaction.Specifically,the Ru-O-Ru atomic clusters exhibited only 86 mV overpotential at 100 mA·cm−^(2) and superior membrane-electrode-assembly activity than commercial Ru/C catalyst.Synchrotron radiation-based Fourier transform infrared spectroscopic measurements revealed that the modification of oxygen in Ru-O-Ru units promoted the reorientation of water molecules from a H-up orientation to H-down,therefore,enhanced the formation of strong hydrogen-bond network of interfacial water on the surface of Ru-O-Ru clusters,leading to enhanced adsorption and dissociation of water and accelerated Volmer step.Those findings provide a potential strategy and deep insights for the development of atomic clusters in electrocatalysts.

Laser-assisted synthesis of PtPd alloy for efficient ethanol oxidation

The inefficiency of ethanol oxidation reaction(EOR)presents a significant obstacle in harnessing renewable biofuels with high energy density into electricity.Despite efforts,most Pt-based catalysts still suffer from drawbacks such as poor activity and susceptibility to CO poisoning,particularly in acidic conditions.Herein,we employed a physical laser-assisted approach to synthetize a PtPd alloy with a 1:1 atomic ratio.This alloy demonstrates remarkable performance in acidic EOR,boasting a high mass activity of 1.86 A·mgPt^(−1)and competitive resistance to poisoning.Combining in situ synchrotron radiation infrared spectroscopy with theoretical calculations,we reveal that the synergic interaction between Pt and Pd enhances both the adsorption of OH*intermediate and the dehydrogenation ability of ethanol.This work will prove the feasibility of synthesizing bimetallic alloys by a physical laser-assisted strategy and promote the development of advanced alloy electrocatalysts.

毛乌素沙地无定河上游河岸沙丘地貌格局及风水交互作用

风水交互作用是干旱半干旱地区常见的地貌现象和重要的地表过程。河岸沙丘是风水交互作用下形成的典型沙丘地貌景观。以毛乌素沙地的无定河流域为研究区,基于遥感影像解译等方法,探明河道与沙丘相互作用的地貌动态变化过程。结果表明:(1)1990—2020年,无定河上游的植被覆盖得到良好恢复,河道两侧流动沙丘逐渐固化,流动沙丘向半固定沙丘转化,半固定沙丘向固定沙丘转化。(2)河道影响了沙丘分布的连续性,使其破碎化,也阻挡了沙丘移动和部分粗粒径沙粒的传输,河流成为一道天然防沙屏障。(3)典型河段河岸沙丘地貌格局呈以河道为中心的带状分布,随着远离河道,依次分布着流动沙丘、半固定沙丘、固定沙丘。风向和河流流向的夹角通过影响风水交互作用的方式和强度,进而影响河岸沙丘的形成与分布。(4)半干旱区河岸沙丘地貌系统与河流水文系统通过水源补给关系保持动态平衡状态,但过度的人类活动可能会打破其阈值,引起沙化程度加大以及河流水文状况的恶化。

高端精密装备精度测量基础理论与方法

完整而精确的测量信息获取是装备设计优化、制造过程调控和服役状态保持的基础,是实现重大装备“上水平”“高性能”的内在要素。本文分析了我国高端精密装备精度测量基础理论发展所面临的重大需求挑战,总结了当前高端精密装备制造精度测量理论、方法与技术领域的主要进展,凝炼了该领域未来5~10年的重大关键科学问题,探讨了前沿研究方向和科学基金资助战略。

Modeling and Stability Issues of Voltage-source Converter-dominated Power Systems:A Review

With the substantive increase in the proportion of voltage-source converter(VSC)-based equipment,traditional power systems that primarily constituted of synchronous generators(SGs)gradually evolved into VSC-dominated ones.At the same time,there is an urgent need for modeling and stability assessment of such systems,since low inertia and weak damping features impair the ability of the systems to resist random disturbances.Existing works model the system dynamic processes from various domains(i.e.,time,frequency and energy),and analyze/determine the system stability under small or large disturbances.Among them,small-signal stability assessments mainly adopt the time-domain analysis based on the state-space model while frequency-domain methods include the impedance model,phase-amplitude dynamics model,and static synchronous generator model.Large-signal stability assessments mainly exploit the time-domain simulation with detailed models(i.e.,continuous/discrete-time mixed model with differentialdifference-algebraic equations),and the energy-domain analysis is based on energy function models.This paper presents a comprehensive review of existing modeling and stability analysis methods for VSC-dominated power systems,including their basic principles,key features,application scenarios and development tendencies.Key technical issues related to modeling and stability analysis are also summarized.

冰期气候突变的高低纬同步性

一项最新发表在Science上的研究表明[1],北极格陵兰岛冰芯记录的末次冰期中发生的气候突变事件与中低纬度的气候变化是同时发生的.由于积雪年复一年的堆积,地球两极的格陵兰岛和南极大陆形成了厚厚的冰盖.冰盖中不同冰层间的微小气泡,保留了当时大气的水分子和其他粒子,为我们了解地质历史时期的地球古气候和古环境提供了独一无二的记录载体.例如,气泡中的化学成分可以记录过去的温室气体(比如二氧化碳)的水平,而火山灰或沙尘则暗示着强大的火山喷发或显著的全球干旱.它们像古生物化石,勾勒出过去特定时段的古气候特征.因此,从冰川或者冰盖中钻取的长冰芯记录,为我们了解地球历史上发生过的复杂气候变化提供了一把钥匙.其中,冰芯中氧同位素比值(δ18O,指质量数为18的氧原子所占比率与标准平均海洋水的偏差再乘以1000)的变化,与当地气温有着密不可分的联系[2],为我们重建过去大气温度的变化提供了可能.

Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation

Actinide-based catalysts have been regarded as promising candidates for N_(2) fixation owing to their unique 5f orbital with flexible oxidation states.Herein,we report for the first time the dispersion of uranium(U)single atoms on TiO_(2) nanosheets via oxygen vacancy confinement for N_(2) electroreduction.The single-atom U catalyst exhibited a high NH_(3) yield of 40.57μg h^(-1) mg^(-1),with a reasonably high Faraday efficiency of 25.77%,ranking first among the reported nitrogen-free catalysts.Isotope-labeling operando synchrotron infrared spectroscopy verifies that the key*N_(2)H_(y) intermediate species was derived from the N_(2) gas of the feed.By using operando X-ray absorption spectroscopy,we found enhanced metal-support interaction between U single atoms and TiO_(2) lattice with more U-O_(latt) coordination under working conditions.Theoretical simulations suggest that the evolved 1O_(ads)-U-4O_(latt) moieties act as a critical electronfeedback center,lowering the thermodynamic energy barrier for the N_(2) dissociation and the first hydrogenation step.This work provides the possibility of tailoring the interaction between metal active sites and supports for designing high-performance actinide-based single-atom catalysts.

Phase separation of the nuclear pore complex facilitates selective nuclear transport to regulate plant defense against pathogen and pest invasion

The nuclear pore complex(NPC),the sole exchange channel between the nucleus and cytoplasm,is composed of several subcomplexes,among which the central barrier determines the permeability/selectivity of the NPC to dominate the nucleocytoplasmic trafficking essential for many important signaling events in yeast and mammals.How plant NPC central barrier controls selective transport is a crucial question remaining to be elucidated.In this study,we uncovered that phase separation of the central barrier is critical for the permeability and selectivity of plant NPC in the regulation of various biotic stresses.Phenotypic assays of nup62 mutants and complementary lines showed that NUP62 positively regulates plant defense against Botrytis cinerea,one of the world’s most disastrous plant pathogens.Furthermore,in vivo imaging and in vitro biochemical evidence revealed that plant NPC central barrier undergoes phase separation to regulate selective nucleocytoplasmic transport of immune regulators,as exemplified by MPK3,essential for plant resistance to B.cinerea.Moreover,genetic analysis demonstrated that NPC phase separation plays an important role in plant defense against fungal and bacterial infection as well as insect attack.These findings reveal that phase separation of the NPC central barrier serves as an important mechanism to mediate nucleocytoplasmic transport of immune regulators and activate plant defense against a broad range of biotic stresses.

Synergistically electronic tuning of metalloid CdSe nanorods for enhanced electrochemical CO_(2) reduction

Engineering the electronic properties of catalysts to target intermediate adsorption energy as well as harvest high selectivity represents a promising strategy to design advanced electrocatalysts for efficient CO_(2) electroreduction.Herein,a synergistical tuning on the electronic structure of the Cd Se nanorods is proposed for boosting electrochemical reduction of CO_(2) .The synergy of Ag doping coupled with Se vacancies tuned the electronic structure of the CdSe nanorods,which shows the metalloid characterization and thereby the accelerated electron transfer of CO_(2) electroreduction.Operando synchrotron radiation Fourier transform infrared spectroscopy and theoretical simulation revealed that the Ag doping and Se vacancies accelerated the CO_(2) activation process and lowered the energy barrier for the conversion from CO_(2) to;COOH;as a result,the performance of CO_(2) electroreduction was enhanced.The as-obtained metalloid Ag-doped CdSe nanorods exhibited a 2.7-fold increment in current density and 1.9-fold Faradaic efficiency of CO compared with the pristine CdSe nanorod.

Coordinately unsaturated nickel single atom electrocatalyst for efficient CO_(2)conversion

Single-atom catalysts(SACs)have shown unexpected catalytic activity due to their unique electronic structure and coordination environment.Nonetheless,the synthesis of an atomically precise low-coordination single-atom catalyst remains a grand challenge.Herein,we report a coordinately unsaturated Ni-N_(3)single-atom electrocatalyst using a metal-organic framework(MOF)derived N-C support with abundant exposed N for excellent electrochemical CO_(2)reduction.The obtained Ni-N_(3)/NC active site exhibited highly efficient CO_(2)-to-CO conversion with a Faradaic efficiency of 94.6%at the current density of 100 mA/cm^(2).In situ X-ray absorption spectroscopy(XAS)measurement suggested that the Ni atomic center with unsaturated coordination had the lower initial chemical state and higher charge transfer ability.In situ Fourier transform infrared(FT-IR)and theoretical calculation results revealed that the unsaturated catalytically active center could facilitate activation of CO_(2)and thus heighten CO_(2)electroreduction activity.These findings provided insights into the rational design of definitive coordination structure of SACs for boosting activity and selectivity.

Fast SHEPWM Solution Method for Wind Power Converter Based on State Equations

Selective harmonic elimination pulse width modula-tion(SHEPWM)is a modulation strategy widely used for three-level wind power grid-connected converters.Its purpose is to eliminate specified sub-low frequency harmonics by controlling switching angle.Furthermore,it can reduce fluctuation of the microgrid system and improve system stability.Intelligent al-gorithms have been applied to the SHEPWM solution process to mitigate calculation complexity associated with the algebraic method,as well as the need to set the initial value.However,disorder of the optimization result causes difficulty in satisfying incremental constraint of the three-level NPC switching angles,and affects the success rate of the algorithm.To overcome this limitation,this paper proposes a fast SHEPWM strategy to optimize the result obtained by the intelligent algorithm.The SHEPWM can be realized by solving switching angles through a state equations-based mathematical model,which is constructed by using the initial variables randomly generated by the intelligent algorithm as the disturbance.This mathematical model improves the success rate of calculation by simplifying constraint representation of switching angles and solving the disorder problem of the optimization result.At the same time,a method based on the circle equation and the trigonometric function is applied to the initial variable assignment of the state equation,which further improves the speed and accuracy of the solution,realizes a more thorough filtering effect,and further reduces the impact of sub-low frequency harmonics on a wind power integrated system.Finally,simulation and experiment results have been used to prove the effectiveness of the proposed SHEPWM strategy when combined with intelligent algorithms.Index Terms-Wind power converter,adaptive genetic algorithm,selective harmonic elimination pulse-width modulation(SHEPWM),state equation,success rate.