Strategies to achieve effective nitrogen activation

Ammonia serves as a crucial chemical raw material and hydrogen energy carrier.Aqueous electrocatalytic nitrogen reduction reaction(NRR),powered by renewable energy,has attracted tremendous interest during the past few years.Although some achievements have been revealed in aqueous NRR,significant challenges have also been identified.The activity and selectivity are fundamentally limited by nitrogen activation and competitive hydrogen evolution.This review focuses on the hurdles of nitrogen activation and delves into complementary strategies,including materials design and system optimization(reactor,electrolyte,and mediator).Then,it introduces advanced interdisciplinary technologies that have recently emerged for nitrogen activation using high-energy physics such as plasma and triboelectrification.With a better understanding of the corresponding reaction mechanisms in the coming years,these technologies have the potential to be extended in further applications.This review provides further insight into the reaction mechanisms of selectivity and stability of different reaction systems.We then recommend a rigorous and detailed protocol for investigating NRR performance and also highlight several potential research directions in this exciting field,coupling with advanced interdisciplinary applications,in situ/operando characterizations,and theoretical calculations.

Construction of MnS/MoS_(2) heterostructure on two-dimensional MoS_(2) surface to regulate the reaction pathways for high-performance Li-O_(2) batteries

The inherent catalytic anisotropy of two-dimensional(2D) materials has limited the enhancement of LiO_(2) batteries(LOBs) performance due to the significantly different adsorption energies on 2D and edge surfaces.Tuning the adsorption strength in 2D materials to the reaction intermediates is essential for achieving high-performance LOBs.Herein,a MnS/MoS_(2) heterostructure is designed as a cathode catalyst by adjusting the adsorption behavior at the surface.Different from the toroidal-like discharge products on the MoS_(2) cathode,the MnS/MoS_(2) surface displays an improved adsorption energy to reaction species,thereby promoting the growth of the film-like discharge products.MnS can disturb the layer growth of MoS_(2),in which the stack edge plane features a strong interaction with the intermediates and limits the growth of the discharge products.Experimental and theoretical results confirm that the MnS/MoS_(2) heterostructure possesses improved electron transfer kinetics at the interface and plays an important role in the adsorption process for reaction species,which finally affects the morphology of Li_2O_(2),In consequence,the MnS/MoS_(2) heterostructure exhibits a high specific capacity of 11696.0 mA h g^(-1) and good cycle stability over 1800 h with a fixed specific capacity of 600 mA h g^(-1) at current density of100 mA g^(-1) This work provides a novel interfacial engineering strategy to enhance the performance of LOBs by tuning the adsorption properties of 2D materials.

High-throughput calculation-based rational design of Fe-doped MoS_(2) nanosheets for electrocatalytic p H-universal overall water splitting

Electrocatalytic water splitting is crucial for H2generation via hydrogen evolution reaction(HER)but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS_(2)nanosheets(SFe-DMNs)were prepared based on the high-throughput density functional theory(DFT)calculation screening.Due to the synergistic effect between Fe atom and MoS_(2)and optimized intermediate binding energy,the SFe-DMNs could deliver outstanding activity for both HER and OER.When assembled into a two-electrode electrolytic cell,the SFe-DMNs could achieve the current density of 50 mA cm^(-2)at a low cell voltage of 1.55 V under neutral condition.These results not only confirmed the effectiveness of high-throughput screening,but also revealed the excellent activity and thus the potential applications in fuel cells of SFe-DMNs.

Single‐pixel terahertz imaging:a review

This paper is devoted to reviewing the results achieved so far in the application of the single-pixel imaging technique to terahertz(THz)systems.The use of THz radiation for imaging purposes has been largely explored in the last twenty years,due to the unique capabilities of this kind of radiation in interrogating material properties.However,THz imaging systems are still limited by the long acquisition time required to reconstruct the object image and significant efforts have been recently directed to overcome this drawback.One of the most promising approaches in this sense is the so-called“single-pixel”imaging,which in general enables image reconstruction by patterning the beam probing the object and measuring the total transmission(or reflection)with a single-pixel detector(i.e.,with no spatial resolution).The main advantages of such technique are that i)no bulky moving parts are required to raster-scan the object and ii)compressed sensing(CS)algorithms,which allow an appropriate reconstruction of the image with an incomplete set of measurements,can be successfully implemented.Overall,this can result in a reduction of the acquisition time.In this review,we cover the experimental solutions proposed to implement such imaging technique at THz frequencies,as well as some practical uses for typical THz applications.

Lithium sulfide:a promising prelithiation agent for high-performance lithium-ion batteries

Lithium-ion batteries are widely used in portable electronics and electric vehicles due to their high energy density,stable cycle life,and low self-discharge.However,irreversible lithium loss during the formation of the solid electrolyte interface greatly impairs energy density and cyclability.To compensate for the lithium loss,introducing an external lithium source,that is,a prelithiation agent,is an effective strategy to solve the above problems.Compared with other prelithiation strategies,cathode prelithiation is more cost-effective with simpler operation.Among various cathode prelithiation agents,we first systematically summarize the recent progress of Li_(2)S-based prelithiation agents,and then propose some novel strategies to tackle the current challenges.This review provides a comprehensive understanding of Li_(2)S-based prelithiation agents and new research directions in the future.

Weakening CO poisoning over size-and support-dependent Pt_(n)/X-graphene catalyst(X=C,B,N,n=1-6,13)

CO poisoning is one of the obstacles for platinum catalysts toward the electro-catalysis process for proton exchange membrane fuel cell(PEMFC)or direct methanol fuel cell(DMFC).Herein,we aim to weaken the CO poisoning on Pt by varying the cluster sizes and supports via doping graphene with B and N based on DFT+D3 calculations.

Single-shot real-time femtosecond imaging of temporal focusing

While the concept of focusing usually applies to the spatial domain,it is equally applicable to the time domain.Realtime imaging of temporal focusing of single ultrashort laser pulses is of great significance in exploring the physics of the space–time duality and finding diverse applications.The drastic changes in the width and intensity of an ultrashort laser pulse during temporal focusing impose a requirement for femtosecond-level exposure to capture the instantaneous light patterns generated in this exquisite phenomenon.Thus far,established ultrafast imaging techniques either struggle to reach the desired exposure time or require repeatable measurements.We have developed single-shot 10-trillion-frame-per-second compressed ultrafast photography(T-CUP),which passively captures dynamic events with 100-fs frame intervals in a single camera exposure.The synergy between compressed sensing and the Radon transformation empowers T-CUP to significantly reduce the number of projections needed for reconstructing a high-quality three-dimensional spatiotemporal datacube.As the only currently available real-time,passive imaging modality with a femtosecond exposure time,T-CUP was used to record the first-ever movie of nonrepeatable temporal focusing of a single ultrashort laser pulse in a dynamic scattering medium.T-CUP’s unprecedented ability to clearly reveal the complex evolution in the shape,intensity,and width of a temporally focused pulse in a single measurement paves the way for single-shot characterization of ultrashort pulses,experimental investigation of nonlinear light-matter interactions,and real-time wavefront engineering for deep-tissue light focusing.

Intense terahertz generation from photoconductive antennas

In this paper,we review the past and recent works on generating intense terahertz(THz)pulses from photoconductive antennas(PCAs).We will focus on two types of large-aperture photoconductive antenna(LAPCA)that can generate high-intensity THz pulses(a)those with large-aperture dipoles and(b)those with interdigitated electrodes.We will first describe the principles of THz generation from PCAs.The critical parameters for improving the peak intensity of THz radiation from LAPCAs are summarized.We will then describe the saturation and limitation process of LAPCAs along with the advantages and disadvantages of working with widebandgap semiconductor substrates.Then,we will explain the evolution of LAPCA with interdigitated electrodes,which allows one to reduce the photoconductive gap size,and thus obtain higher bias fields while applying lower voltages.We will also describe recent achievements in intense THz pulses generated by interdigitated LAPCAs based on wide-bandgap semiconductors driven by ampli-fied lasers.Finally,we will discuss the future perspectives of THz pulse generation using LAPCAs.

Single-shot compressed ultrafast photography: a review

Compressed ultrafast photography(CUP)is a burgeoning single-shot computational imaging technique that provides an imaging speed as high as 10 trillion frames per second and a sequence depth of up to a few hundred frames.This technique synergizes compressed sensing and the streak camera technique to capture nonrepeatable ultrafast transient events with a single shot.With recent unprecedented technical developments and extensions of this methodology,it has been widely used in ultrafast optical imaging and metrology,ultrafast electron diffraction and microscopy,and information security protection.We review the basic principles of CUP,its recent advances in data acquisition and image reconstruction,its fusions with other modalities,and its unique applications in multiple research fields.

High-spatial-resolution ultrafast framing imaging at 15 trillion frames per second by optical parametric amplification

We report a framing imaging based on noncollinear optical parametric amplification(NCOPA),named FINCOPA,which applies NCOPA for the first time to single-shot ultrafast optical imaging.In an experiment targeting a laser-induced air plasma grating,FINCOPA achieved 50 fs-resolved optical imaging with a spatial resolution of^83 lp∕mm and an effective frame rate of 10 trillion frames per second(Tfps).It has also successfully visualized an ultrafast rotating optical field with an effective frame rate of 15 Tfps.FINCOPA has simultaneously a femtosecond-level temporal resolution and frame interval and a micrometer-level spatial resolution.Combining outstanding spatial and temporal resolutions with an ultrahigh frame rate,FINCOPA will contribute to high-spatiotemporal resolution observations of ultrafast transient events,such as atomic or molecular dynamics in photonic materials,plasma physics,and laser inertial-confinement fusion.

Single-shot spectral-volumetric compressed ultrafast photography

In ultrafast optical imaging,it is critical to obtain the spatial structure,temporal evolution,and spectral composition of the object with snapshots in order to better observe and understand unrepeatable or irreversible dynamic scenes.However,so far,there are no ultrafast optical imaging techniques that can simultaneously capture the spatial–temporal–spectral five-dimensional(5D)information of dynamic scenes.To break the limitation of the existing techniques in imaging dimensions,we develop a spectral-volumetric compressed ultrafast photography(SV-CUP)technique.In our SV-CUP,the spatial resolutions in the x,y and z directions are,respectively,0.39,0.35,and 3 mm with an 8.8 mm×6.3 mm field of view,the temporal frame interval is 2 ps,and the spectral frame interval is 1.72 nm.To demonstrate the excellent performance of our SV-CUP in spatial–temporal–spectral 5D imaging,we successfully measure the spectrally resolved photoluminescent dynamics of a 3D mannequin coated with CdSe quantum dots.Our SV-CUP brings unprecedented detection capabilities to dynamic scenes,which has important application prospects in fundamental research and applied science.

High-fidelity image reconstruction for compressed ultrafast photography via an augmented-Lagrangian and deep-learning hybrid algorithm

Compressed ultrafast photography(CUP) is the fastest single-shot passive ultrafast optical imaging technique,which has shown to be a powerful tool in recording self-luminous or non-repeatable ultrafast phenomena.However, the low fidelity of image reconstruction based on the conventional augmented-Lagrangian(AL)and two-step iterative shrinkage/thresholding(Tw IST) algorithms greatly prevents practical applications of CUP, especially for those ultrafast phenomena that need high spatial resolution. Here, we develop a novel AL and deep-learning(DL) hybrid(i.e., AL+DL) algorithm to realize high-fidelity image reconstruction for CUP. The AL+DL algorithm not only optimizes the sparse domain and relevant iteration parameters via learning the dataset but also simplifies the mathematical architecture, so it greatly improves the image reconstruction accuracy. Our theoretical simulation and experimental results validate the superior performance of the AL+DL algorithm in image fidelity over conventional AL and Tw IST algorithms, where the peak signalto-noise ratio and structural similarity index can be increased at least by 4 d B(9 d B) and 0.1(0.05) for a complex(simple) dynamic scene, respectively. This study can promote the applications of CUP in related fields, and it will also enable a new strategy for recovering high-dimensional signals from low-dimensional detection.

High-speed dual-view band-limited illumination profilometry using temporally interlaced acquisition

We report dual-view band-limited illumination profilometry(BLIP)with temporally interlaced acquisition(TIA)for high-speed,three-dimensional(3D)imaging.Band-limited illumination based on a digital micromirror device enables sinusoidal fringe projection at up to 4.8 kHz.The fringe patterns are captured alternately by two high-speed cameras.A new algorithm,which robustly matches pixels in acquired images,recovers the object’s 3D shape.The resultant TIA–BLIP system enables 3D imaging over 1000 frames per second on a field of view(FOV)of up to 180 mm×130 mm(corresponding to 1180×860 pixels)in captured images.We demonstrated TIA–BLIP’s performance by imaging various static and fast-moving 3D objects.TIA–BLIP was applied to imaging glass vibration induced by sound and glass breakage by a hammer.Compared to existing methods in multiview phase-shifting fringe projection profilometry,TIA–BLIP eliminates information redundancy in data acquisition,which improves the 3D imaging speed and the FOV.We envision TIA–BLIP to be broadly implemented in diverse scientific studies and industrial applications.

Multitask deep-learning-based design of chiral plasmonic metamaterials

The field of chiral plasmonics has registered considerable progress with machine-learning(ML)-mediated metamaterial prototyping,drawing from the success of ML frameworks in other applications such as pattern and image recognition.Here,we present an end-to-end functional bidirectional deep-learning(DL)model for three-dimensional chiral metamaterial design and optimization.This ML model utilizes multitask joint learning features to recognize,generalize,and explore in detail the nontrivial relationship between the metamaterials’geometry and their chiroptical response,eliminating the need for auxiliary networks or equivalent approaches to stabilize the physically relevant output.Our model efficiently realizes both forward and inverse retrieval tasks with great precision,offering a promising tool for iterative computational design tasks in complex physical systems.Finally,we explore the behavior of a sample ML-optimized structure in a practical application,assisting the sensing of biomolecular enantiomers.Other potential applications of our metastructure include photodetectors,polarization-resolved imaging,and circular dichroism(CD)spectroscopy,with our ML framework being applicable to a wider range of physical problems.

Remarkable catalysis of spinel ferrite XFe2O4(X=Ni,Co,Mn,Cu,Zn)nanoparticles on the dehydrogenation properties of LiAlH_(4):An experimental and theoretical study

Safe,compact,lightweight and cost-effective hydrogen storage is one of the main challenges that need to be addressed to effectively deploy the hydrogen economy.LiAlH_(4),as a solid-state hydrogen storage material,presents several advantages such as high hydrogen storage capacity,low price and abundant sources.Unfortunately,neither thermodynamic nor kinetic properties of dehydrogenation for LiAlH_(4)can fulfill the requirements of practical application.Thus,a series of spinel ferrite nanoparticles such as XFe_(2)O_(4)(X=Ni,Co,Mn,Cu,Zn,Fe)were prepared by using the modified thermal decomposition method,and then doped into LiAlH_(4)by using ball milling.Our results show that LiAlH_(4)doped with 7 wt%NiFe_(2)O_(4)starts to release hydrogen at 69.1°C,and the total amount of hydrogen released is 7.29 wt%before 300°C.The activation energies of the two-step hydrogen release reactions of LiAlH_(4)doped with 7 wt%NiFe_(2)O_(4)are 42.32 kJ mol^(-1)and 71.42 k J mol,which are 59.0%and 63.6%lower than those of as-received LiAlH_(4),respectively.Combining the density functional theory(DFT)calculations,we reveal that both the presence of Ni FeOand in-situ formed AlNiin ball-milling decrease the desorption energy barrier of Al-H bonding in LiAlH_(4)and accelerate the breakdown of Al-H bonding through the interfacial charge transfer and the dehybridization of the Al-H cluster.Thus,the experimental and theoretical results open a new avenue toward designing high effective catalysts applied to LiAlH_(4)as a candidate for hydrogen storage.

Recent advancements in plasmon-enhanced visible light-driven water splitting

Recently,the combination of plasmonic noble metallic nanostructures with semiconductors for plasmonenhanced visible light-driven water splitting(WS)has attracted considerable attention.This review first presents three prime enhancement mechanisms for plasmon-enhanced photocatalytic WS,and then some state-of-the-art representative studies are introduced according to different enhancement mechanisms.Furthermore,the design parameters of plasmonic-metal/semiconductor photocatalysts are discussed in detail,focusing on the effect of shape,size and geometric position of metallic nanostructures on the photocatalytic activity of visible light-driven WS.Finally,the challenges and perspectives for plasmon-enhanced solar WS are proposed.

Single-shot real-time compressed ultrahigh-speed imaging enabled by a snapshot-to-video autoencoder

Single-shot 2 D optical imaging of transient scenes is indispensable for numerous areas of study.Among existing techniques,compressed optical-streaking ultrahigh-speed photography(COSUP)uses a cost-efficient design to endow ultrahigh frame rates with off-the-shelf CCD and CMOS cameras.Thus far,COSUP’s application scope is limited by the long processing time and unstable image quality in existing analytical-modeling-based video reconstruction.To overcome these problems,we have developed a snapshot-to-video autoencoder(S2 V-AE)—which is a deep neural network that maps a compressively recorded 2 D image to a movie.The S2 V-AE preserves spatiotemporal coherence in reconstructed videos and presents a flexible structure to tolerate changes in input data.Implemented in compressed ultrahigh-speed imaging,the S2 V-AE enables the development of single-shot machine-learning assisted real-time(SMART)COSUP,which features a reconstruction time of 60 ms and a large sequence depth of 100 frames.SMART-COSUP is applied to wide-field multiple-particle tracking at 20,000 frames per second.As a universal computational framework,the S2 V-AE is readily adaptable to other modalities in high-dimensional compressed sensing.SMART-COSUP is also expected to find wide applications in applied and fundamental sciences.

Guanine-assisted N-doped ordered mesoporous carbons as efficient capacity decaying suppression materials for lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries are considered promising next-generation energy storage devices due to their high weight capacities and theoretical energy densities,which are significantly higher than those of conventional lithium-ion batteries.However,the sulfur cathode presents two major drawbacks,specifically low specific capacity caused by the poor electrical conductivities of the active materials and fast capacity decay caused by polysulfide dissolution/shuttling.Herein,a high-rate and high-stability dendritic material consisting of N-doped ordered mesoporous carbons(NOMCs)was successfully synthesized via a facile and low-cost calcination method.The highly ordered mesoporous carbon skeleton limited the growth of the sulfur nanofiller within its channels and provided the necessary electrical contact with the insulating sulfur.Furthermore,N-doped heteroatoms presented strong binding sites for trapping polysulfide intermediates,achieving high electrochemical activity,which promoted polysulfide conversion reactions.As a result,the prepared NOMC-2/S cathode material with 1.2-1.5 mg cm^(-2)of sulfur displayed excellent electrochemical performance with a high-rate capability of 460.5 m Ah g^(-1)at 1 C,a high specific capacity of 530.9 m Ah g^(-1)after 200 cycles at 0.1 C,and a decay rate of~0.19%per cycle.

Dynamical evolution of Ge quantum dots on Si(111):From island formation to high temperature decay

Heteroepitaxial growth is a process of profound fundamental importance as well as an avenue to realize nanostructures such as Ge/Si quantum dots(QDs),with appealing properties for applications in opto-and nanoelectronics.However,controlling the Ge/Si QD size,shape,and composition remains a major obstacle to their practical implementation.Here,Ge nanostructures on Si(111)were investigated in situ and in real-time by low energy electron microscopy(LEEM),enabling the observation of the transition from wetting layer formation to 3D island growth and decay.The island size,shape,and distribution depend strongly on the growth temperature.As the deposition temperature increases,the islands become larger and sparser,consistent with Brownian nucleation and capture dynamics.At 550◦C,two distinct Ge/Si nanostructures are formed with bright and dark appearances that correspond to flat,atoll-like and tall,faceted islands,respectively.During annealing,the faceted islands increase in size at the expense of the flat ones,indicating that the faceted islands are thermodynamically more stable.In contrast,triangular islands with uniform morphology are obtained from deposition at 600◦C,suggesting that the growth more closely follows the ideal shape.During annealing,the islands formed at 600◦C initially show no change in morphology and size and then rupture simultaneously,signaling a homogeneous chemical potential of the islands.These observations reveal the role of dynamics and energetics in the evolution of Ge/Si QDs,which can serve as a step towards the precise control over the Ge nanostructure size,shape,composition,and distribution on Si(111).