2D CoOOH Sheet-Encapsulated Ni2P into Tubular Arrays Realizing 1000 mA cm^-2-Level-Current-Density Hydrogen Evolution Over 100 h in Neutral Water

Water electrolysis at high current density(1000 mA cm-2 level)with excellent durability especially in neutral electrolyte is the pivotal issue for green hydrogen from experiment to industrialization.In addition to the high intrinsic activity determined by the electronic structure,electrocatalysts are also required to be capable of fast mass transfer(electrolyte recharge and bubble overflow)and high mechanical stability.Herein,the 2D CoOOH sheet-encapsulated Ni2P into tubular arrays electrocatalytic system was proposed and realized 1000 mA cm-2-levelcurrent-density hydrogen evolution over 100 h in neutral water.In designed catalysts,2D stack structure as an adaptive material can buffer the shock of electrolyte convection,hydrogen bubble rupture,and evolution through the release of stress,which insure the long cycle stability.Meanwhile,the rich porosity between stacked units contributed the good infiltration of electrolyte and slippage of hydrogen bubbles,guaranteeing electrolyte fast recharge and bubble evolution at the high-current catalysis.Beyond that,the electron structure modulation induced by interfacial charge transfer is also beneficial to enhance the intrinsic activity.Profoundly,the multiscale coordinated regulation will provide a guide to design high-efficiency industrial electrocatalysts.

Trajectory engineering via a space-fractional Schrodinger equation with dynamic linear index potential

We theoretically and numerically study the propagation dynamics of a Gaussian beam modeled by the fractional Schrodinger equation with different dynamic linear potentials. For the limited case α = 1(α is the Lévy index) in the momentum space, the beam suffers a frequency shift which depends on the applied longitudinal modulation and the involved chirp. While in the real space, by precisely controlling the linear chirp, the beam will exhibit two different evolution characteristics: one is the zigzag trajectory propagation induced by multi-reflection occurring at the zeros of spatial spectrum,the other is diffraction-free propagation. Numerical simulations are in full accordance with the theoretical results. Increase of the Lévy index not only results in the drift of those turning points along the transverse direction, but also leads to the delocalization of the Gaussian beam.

Sequential reactant water management by complementary multisite catalysts for surpassing platinum hydrogen evolution activity

Alkaline hydrogen evolution reaction(HER)offers a near-zero-emission approach to advance hydrogen energy.However,the activity limited by the multiple reaction steps involving H_(2)O molecules transfer,absorption,and activation still unqualified the thresholds of economic viability.Herein,we proposed a multisite complementary strategy that incorporates hydrophilic Mo and electrophilic V into Ni-based catalysts to divide the distinct steps on atomically dispersive sites and thus realize sequential regulation of the HER process.The Isotopic labeled in situ Raman spectroscopy describes 4-coordinated hydrogen bonded H_(2)O to be free H_(2)O passing the inner Helmholtz plane in the vicinity of the catalysts under the action of hydrophilic Mo sites.Furthermore,potential-dependent electrochemical impedance spectroscopy(EIS)reveals that electrophilic V sites with abundant 3d empty orbitals could activate the lone-pair electrons in the free H_(2)O molecules to produce more protic hydrogen,and dimerize into H_(2) at the Ni sites.By the sequential management of reactive H_(2)O molecules,NiMoV oxides multisite catalysts surpass Pt/C hydrogen evolution activity(49 mV@10 mA∙cm^(-2) over 140 h).Profoundly,this study provides a tangible model to deepen the comprehension of the catalyst–electrolyte interface and create efficient catalysts for diverse reactions.

Interface engineering via molecules/ions/groups for electrocatalytic water splitting

The electrochemical water splitting to produce hydrogen converts electric energy into clean hydrogen energy,which is a groundbreaking concept of energy optimization.To achieve high efficiency,numerous strategies have been developed to enhance the performance of electrocatalysts.Among these,interface engineering with molecules/ions/groups,serves as a versatile approach for optimizing the performance of electrocatalysts in water splitting.On the basis of numerous achievements in high-performance electrocatalysts engineered through molecules/ions/groups at interface,a comprehensive understanding of these advancements is crucial for guiding future progress.Herein,after providing a concise overview of the background,the interface engineering via molecules/ions/groups for electrocatalytic water splitting is demonstrated from three perspectives.Firstly,the engineering of electronic state of electrocatalysts by molecules/ions/groups at interface to reduce the Gibbs free energy of the corresponding reactions.Secondly,the modification of local microenvironment surrounding electrocatalysts via molecules/ions/groups at interface to enhance the transfer of reactants and products.Thirdly,the protection of electrocatalysts with molecule/ion/group fences improves their durability,including protecting active sites from leaching and defending them against harmful species.The fundamental principles of these three aspects are outlined for each,along with pertinent comments.Finally,several research directions and challenges are proposed.

Nanopore-rich NiFe LDH targets the formation of the high-valent nickel for enhanced oxygen evolution reaction

Nickel-iron layered double hydroxides(NiFe LDHs)represent a promising candidate for oxygen evolution reaction(OER),however,are still confronted with insufficient activity,due to the slow kinetics of electrooxidation of Ni^(2+)cations for the high-valent active sites.Herein,nanopore-rich NiFe LDH(PR-NiFe LDH)nanosheets were proposed for enhancing the OER activity together with stability.In the designed catalyst,the confined nanopores create abundant unsaturated Ni sites at edges,and decrease the migration distance of protons down to the scale of their mean free path,thus promoting the formation of high-valent Ni^(3+)/^(4+)active sites.The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation.Thus,the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm^(−2)and a small Tafel slope of 75 mV∙dec^(−1),which are competitive among the advanced LDHs based catalysts.Moreover,the RP-NiFe LDH catalyst was implemented in anion exchange membrane(AEM)water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h.These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer.This concept also provides valuable insights into the design of other catalysts for OER and beyond.

Operando reconstruction towards stable CuI nanodots with favorable facets for selective CO_(2) electroreduction to C2H4

Cu-based electrocatalysts with favorable facets and Cu^(+)can boost CO_(2) reduction to valuable multicarbon products.However,the inevitable Cu^(+)reduction and the phase evolution usually result in poor performance.Herein,we fabricate CuI nanodots with favorable(220)facets and a stable Cu^(+)state,accomplished by operando reconstruction of Cu(OH)_(2) under CO_(2)-and I--containing electrolytes for enhanced CO_(2)-to-C_(2)H_(4) conversion.Synchrotron X-ray absorption spectroscopy(XAS),in-situ Raman spectroscopy and thermodynamic potential analysis reveal the preferred formation of CuI.Vacuum gas electroresponse and density functional theory(DFT)calculations reveal that CO_(2)-related species induce the exposure of the(220)plane of Cu I.Moreover,the small size of nanodots enables the adequate contact with I^(-),which guarantees the rapid formation of Cu I instead of the electroreduction to Cu^(0).As a result,the resulting catalysts exhibit a high C2H4 Faradaic efficiency of 72.4%at a large current density of 800 m A cm^(-2) and robust stability for 12 h in a flow cell.Combined in-situ ATR-SEIRS spectroscopic characterizations and DFT calculations indicate that the(220)facets and stable Cu^(+) in CuI nanodots synergistically facilitate CO_(2)/*CO adsorption and*CO dimerization.

非厄米梯度超构表面中的奇异点及其最大螺旋二色性

螺旋二色性利用无限的轨道角动量自由度,可以突破依赖于固有自旋自由度的圆二色性所受到的两态限制,为探索经典波体系中的手性效应提供了重要的手段.然而,在波与物质相互作用过程中,手性信号通常非常微弱,使得螺旋手性效应的有效增强极具挑战性.本文通过在非厄米梯度超构表面的内禀拓扑荷中构建手性奇异点,提出了一种实现最大螺旋二色性的新范式.由于奇异点所诱发的非对称手性耦合特性,非厄米梯度超构表面可以通过灵活地设计,实现多样化的极端手性调控:一种手性的涡旋场被非厄米超构表面完全反射,而相反手性的涡旋场则可以被完美吸收或传输到定制的涡旋模式.作为最大螺旋二色性的一种体现,本文提出完美手性选择的涡旋传输现象,并通过声学实验进行了验证.本研究为实现最大手性效应以及探索波与物质相互作用中的手性物理提供了新途径,有望推动诸如非对称手性调控、单向传播和信息多路复用等轨道角动量相关的基础研究和应用领域的发展.

Chemical-vapor-deposition-grown 2D transition metal dichalcogenides:A generalist model for engineering electrocatalytic hydrogen evolution

Two-dimensional(2D)transition metal dichalcogenides(TMDs)have proved to possess exceptional catalytic performance for hydrogen evolution and are considered to be an appropriate substitute for commercial Pt-based catalysts.Experimentally,chemical vapor deposition(CVD)is an extremely important technique for acquiring controllable and high-purity TMDs for electrocatalysis and modern electronic devices.Recently,researchers have made significant achievements in synthesizing TMDs used for electrocatalytic hydrogen evolution by CVD ranging from dynamic mechanism exploration to performance optimization.In this review,we present the recent progress based on electrocatalytic hydrogen evolution implemented by CVDgrowth TMDs nanosheets and unveil the structural–activity correlation.Firstly,in synthesis,diverse factors covering precursor,substrate,temperature settings,and atmosphere will affect the quality and surface morphology of TMDs.Then,we present the current research status of the CVD-grown 2D TMDs for engineering electrocatalytic hydrogen evolution,including intrinsic performance exploring,morphology engineering,composition adjusting,phase engineering,and vertically-oriented structure constructing.Finally,the future prospects and challenges of CVD in 2D TMDs electrocatalysis are provided.

透过散射层对运动三维物体的单次曝光录像

透过散射介质成像在很多领域都有重要应用。然而,目前关于针对三维运动物体的透过散射介质成像与追踪的研究却很少。提出一种透过散射层对运动三维物体进行单次曝光录像的方法。从散射层两个不同位置出射的散斑之间非相关且包含了双视角下的物体信息,在这两部分散斑的重叠区域进行探测,可实现三维成像。在曝光过程中绕光轴旋转相机,可探测到由一系列旋转不同角度后的瞬时散斑叠加而成的一张散斑图像。在满足散斑旋转去相关的条件下,这些瞬时散斑之间非相关。至此,对应不同时刻、不同视角的一系列瞬时散斑多路复用于一张散斑图像中。利用互相关解卷积成像法,通过依次旋转各个单视角下探测的点扩展函数,即可从这张散斑图像中重建出三维运动物体的视频信息。

Multi-scale regulation in S,N co-incorporated carbon encapsulated Fe-doped CO_(9)S_(8) achieving efficient water oxidation with low overpotential

Sulfide compounds provide a type of promising alternative for oxygen evolution reaction(OER)electrocatalysts due to their diversity,intrinsic activities,low-price and earth-abundance.However,the unsmooth mass transport channel,the collapse of the structure and insufficient intrinsic activities limit their potential for OER performance.In respond,the dense Fe-doped Co_(9)S_(8) nanoparticles encapsulated by S,N co-incorporated carbon nanosheets(Fe-Co_(9)S_(8)@SNC)were proposed and synthesized via fast thermal treatment from ultrathin metal-organic frameworks(MOFs)nanosheets.In designed catalysts,the nanosheet configuration connected by nanoparticles retained rich access for permeation of electrolyte and precipitation of O_(2) bubbles during OER process.Meanwhile,the outer carbon layer of Co9S8 provided additional catalytic activity while acting as armor to keep the structure stability.At the atomic scale,the doped Fe regulated the local charge density and the d-band center for facilitating desorption of oxygen intermediates.Benefiting from this multi-scale regulation strategy,the Fe-Co_(9)S_(8)@SNC displays an ultralow overpotential of 273 mV at 10 mA·cm^(-2) and small Tafel slope of 55.8 mV·dec^(-1),which is even close to the benchmark RuO_(2) catalyst.This concept could provide valuable insights into the design of other catalysts for OER and beyond.

Single MoTe_(2) sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies engineering

Activating basal plane inert sites will endow MoTe_(2) with prominent hydrogen evolution reaction(HER)catalytic capability and arouse a new family of HER catalysts.Herein,we fabricated single MoTe_(2) sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies introducing.Through the extraction of electrical parameters of single MoTe_(2) sheet,the in-plane and interlayer conductivities were optimized effectively by Te vacancies due to the defect levels.More deeply,Te vacancies can induce the delocalization of electrons around Mo atoms and shift the d-band center,as a consequence,facilitate the adsorption of H from the catalyst surface for HER catalysis.Benefiting by the coordinated regulation of band structure and local charge density,the overpotential at−10 mA·cm^(−2)was reduced to 0.32 V after Te vacancies compared to 0.41 V for the basal plane sites of same MoTe_(2) nanosheet.Meanwhile,the insights gained from single nanosheet electrocatalytic microdevice can be applied to the improved HER of the commercial MoTe_(2) power.That the in situ testing of the atomic structure-electrical behavior-electrochemical properties of a single nanosheet before/after vacancies introducing provides reliable insight to structure-activity relationships.

Asymmetric nonlinear-mode-conversion in an optical waveguide with PT symmetry

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect,while it is challenging to achieve asymmetric nonlinear-mode-conversion(NMC)due to the limitations imposed by phase-matching.In this work,we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequencydoubling process and periodic PT symmetric modulation in an optical waveguide.By engineering the one-way momentum from PT symmetric modulation,we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes.Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry,which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.

1T′-MoTe_(2)-Based On-Chip Electrocatalytic Microdevice:A Platform to Unravel Oxidation-Dependent Electrocatalysis

Ultrathin transition metal dichalcogenides(TMDs)are of particular interest as low-cost alternatives to highly active electrocatalysts because of their high surface activation energy.However,their striking structural characteristics cause chemical instability and undergo oxidation easily.

A WEDGE DISCLINATION DIPOLE INTERACTING WITH A COATED CYLINDRICAL INHOMOGENEITY

A three-phase composite cylinder model is utilized to study the interaction of a wedge disclination dipole with a coated cylindrical inhomogeneity. The explicit expression of the force acting on the wedge disclination dipole is calculated. The motilities and the equilibrium po- sitions of the disclination dipole near the coated inhomogeneity are discussed for various material combinations, relative thicknesses of the coating layer and the features of the disclination dipole. The results show that the material properties of the coating layer have a major part to play in alteringi the strengthening effect or toughening effect produced by the coated inhomogeneity.