Preparation of MXene-based hybrids and their application in neuromorphic devices

The traditional von Neumann computing architecture has relatively-low information processing speed and high power consumption,making it difficult to meet the computing needs of artificial intelligence(AI).Neuromorphic computing systems,with massively parallel computing capability and low power consumption,have been considered as an ideal option for data storage and AI computing in the future.Memristor,as the fourth basic electronic component besides resistance,capacitance and inductance,is one of the most competitive candidates for neuromorphic computing systems benefiting from the simple structure,continuously adjustable conductivity state,ultra-low power consumption,high switching speed and compatibility with existing CMOS technology.The memristors with applying MXene-based hybrids have attracted significant attention in recent years.Here,we introduce the latest progress in the synthesis of MXene-based hybrids and summarize their potential applications in memristor devices and neuromorphological intelligence.We explore the development trend of memristors constructed by combining MXenes with other functional materials and emphatically discuss the potential mechanism of MXenes-based memristor devices.Finally,the future prospects and directions of MXene-based memristors are briefly described.

Interfacial engineering of holey platinum nanotubes for formic acid electrooxidation boosted water splitting

Both structure and interface engineering are highly effective strategies for enhancing the catalytic activity and selectivity of precious metal nanostructures.In this work,we develop a facile pyrolysis strategy to synthesize the high-quality holey platinum nanotubes(Pt-H-NTs)using nanorods-like Pt^(Ⅱ)-phenanthroline(PT)coordination compound as self-template and self-reduction precursor.Then,an up-bottom strategy is used to further synthesize polyallylamine(PA)modified Pt-H-NTs(Pt-HNTs@PA).PA modification sharply promotes the catalytic activity of Pt-H-NTs for the formic acid electrooxidation reaction(FAEOR)by the direct reaction pathway.Meanwhile,PA modification also elevates the catalytic activity of Pt-H-NTs for the hydrogen evolution reaction(HER)by the proton enrichment at electrolyte/electrode interface.Benefiting from the high catalytic activity of Pt-H-NTs@PA for both FAEOR and HER,a two-electrode FAEOR boosted water electrolysis system is fabricated by using Pt-H-NTs@PA as bifunctio nal electrocatalysts.Such FAEOR boosted water electrolysis system only requires the operational voltage of 0.47 V to achieve the high-purity hydrogen production,showing an energy-saving hydrogen production strategy compared to traditional water electrolysis system.

Spontaneous decoration of ionic compounds at perovskite interfaces to achieve 23.38% efficiency with 85% fill factor in NiO_X-based perovskite solar cells

Inorganic hole transport materials, particularly NiO_X, have shown considerable promise in boosting the efficiency and stability of perovskite solar cells. However, a major barrier to commercialization of NiO_X-based perovskite solar cells with positive-intrinsic-negative architectures is their direct contact with the absorbing layer, which can lead to losses of photovoltage and fill factor. Furthermore, highly positive under-coordinated Ni cations degrade the perovskite at the interface. Here, we address these issues with the use of an ionic compound(QAPyBF_(4)) as an additive to passivate defects throughout the perovskite layer and improve carrier conduction and interactions with under-coordinated Ni cations. Specifically,the highly electronegative inorganic anion [BF_(4)]~- interacts with the NiO_x/perovskite interface to passivate under-coordinated cations(Ni^(≥3+)). Accordingly, the decorated cells achieved a power conversion efficiency of 23.38% and a fill factor of 85.5% without a complex surface treatment or NiO_X doping.

Bifunctional PdPt bimetallenes for formate oxidation-boosted water electrolysis

Small-molecule electrooxidation-boosted water electrolysis(WE)is an energy-saving method for hydrogen(H2)production.Herein,PdPt bimetallenes(PdPt BMLs)are obtained through the simple galvanic replacement reaction.PdPt BMLs reveal 2.93-fold enhancement in intrinsic electroactivity and 4.53-fold enhancement in mass electroactivity for the formate oxidation reaction(FOR)with respect to Pd metallenes(Pd MLs)at 0.50 V potential due to the synergistic effect.Meanwhile,the introduction of Pt atoms also considerably increases the electroactivity of PdPt BMLs for hydrogen evolution reaction(HER)with respect to Pd MLs in an alkaline medium,which even exceeds that with the use of commercial Pt nanocrystals.Inspired by the outstanding FOR and HER electroactivity of bifunctional PdPt BMLs,a two-electrode FOR-boosted WE system(FOR-WE)is constructed by using PdPt BMLs as the cathode and the anode.The FOR-WE system only requires an operational voltage of 0.31 V to achieve H2 production,which is 1.48 V lower than that(ca.1.79 V)with the use of the traditional WE system.

Photonic crystal-connected bidirectional micro-ring resonator array for duplex mode and wavelength channel(de)multiplexing

The progress of on-chip optical communication relies on integrated multi-dimensional mode(de)multiplexers to enhance communication capacity and establish comprehensive networks.However,existing multi-dimensional(de)multiplexers,involving modes and wavelengths,face limitations due to their reliance on single-directional total internal reflection and multi-level mode conversion based on directional coupling principles.These constraints restrict their potential for full-duplex functionality and highly integrated communication.We solve these problems by introducing a photonic-like crystal-connected bidirectional micro-ring resonator array(PBMRA)and apply it to duplex mode-wavelength multiplexing communication.The directional independence of total internal reflection and the cumulative effect of the subwavelength-scale pillar within the single-level photonic crystal enable bidirectional mode and wavelength multiplexed signals to transmit among multi-pair nodes without interference,improving on-chip integration in single-level mode conversion.As a proof of concept,we fabricated a nine-channel bidirectional multi-dimensional(de)multiplexer,featuring three wavelengths and three TE modes,compactly housed within a footprint of 80μm×80μm,which efficiently transmits QPSK-OFDM signals at a rate of 216 Gbit/s,achieving a bit error rate lower than 10^(-4).Leveraging the co-ring transmission characteristic and the orthogonality of the mode-wavelength channel,this(de)multiplexer also enables a doubling of communication capacity using two physical transmission channels.

Phase separation and domain crystallinity control enable open-air-printable highly efficient and sustainable organic photovoltaics

Organic solar cells(OSCs)have emerged as a promising solution for sustainable energy production,offering advantages such as a low carbon footprint,short energy payback period,and compatibility with eco-solvents.However,the use of hazardous solvents continues to dominate the best-performing OSCs,mainly because of the challenges of controlling phase separation and domain crystallinity in eco-solvents.In this study,we combined the solvent vapor treatment of CS2 and thermal annealing to precisely control the phase separation and domain crystallinity in PM6:M-Cl and PM6:O-Cl systems processed with the eco-solvent o-xylene.This method resulted in a maximum power conversion efficiency(PCE)of 18.4%,which is among the highest values reported for sustainable binary OSCs.Furthermore,the fabrication techniques were transferred from spin coating in a nitrogen environment to blade printing in ambient air,retaining a PCE of 16.0%,showing its potential for high-throughput and scalable production.In addition,a comparative analysis of OSCs processed with hazardous and green solvents was conducted to reveal the differences in phase aggregation.This work not only underscores the significance of sustainability in OSCs but also lays the groundwork for unlocking the full potential of open-air-printable sustainable OSCs for commercialization.

Step-scheme ZnO@ZnS hollow microspheres for improved photocatalytic H_(2) production performance

Constructing a step-scheme heterojunction at the interface between two semiconductors is an efficient way to optimize the redox ability and accelerate the charge carrier separation of a photocatalytic system for achieving high photocatalytic performance.In this study,we prepared a hierarchical ZnO@ZnS step-scheme photocatalyst by incorporating ZnS into the outer shell of hollow ZnO microspheres via a simple in situ sulfidation strategy.The ZnO@ZnS step-scheme photocatalysts had a large surface area,high light utilization capacity,and superior separation efficiency for photogenerated charge carriers.In addition,the material simulation revealed that the formation of the step-scheme heterojunction between ZnO and ZnS was due to the presence of the built-in electric field.Our study paves the way for design of high-performance photocatalysts for H_(2) production.

g-C_(3)N_(4)/CoTiO_(3) S-scheme heterojunction for enhanced visible light hydrogen production through photocatalytic pure water splitting

Photocatalytic hydrogen(H_(2))production via water splitting in the absence of sacrificial agents is a promising strategy for producing clean and sustainable hydrogen energy from solar energy.However,the realization of a photocatalytic pure water splitting system with desirable efficiency is still a huge challenge.Herein,visible light photocatalytic H_(2) production from pure water splitting was successfully achieved using a g-C_(3)N_(4)/CoTiO_(3) S-scheme heterojunction photocatalyst in the absence of sacrificial agents.An optimum hydrogen evolution rate of 118μmol∙h^(−1)∙g^(−1) was reached with the addition of 1.5 wt%CoTiO_(3).The remarkably promoted hydrogen evolution rate was attributed to the intensified light absorption coupled with the synergistic effect of visible light responsive CoTiO_(3),the promoted efficiency in charge separation,and the reserved strong redox capacity induced by the S-scheme charge transfer mechanism.This work provides an alternative to visible light-responding oxidation photocatalysts for the construction of S-scheme heterojunctions and high-efficiency photocatalytic systems for pure water splitting.

Air-Processed Efficient Organic Solar Cells from Aromatic Hydrocarbon Solvent without Solvent Additive or Post-Treatment:Insights into Solvent Effect on Morphology

Most of the recent organic solar cells(OSCs)with top-of-the-line efficiencies are processed from organic solvents with a high vapor pressure such as CF in nitrogen-filled glovebox,which is not feasible for large-area manufacturing.Herein,we cast active layers with both aromatic hydrocarbon solvents and halogenated solvents without any solvent additive or post-treatment,as well as interlayers with water and methanol in air(35%relative humidity)for efficient OSCs,except cathode electrode's evaporation is in vacuum.Compared to the PM6:Y6 system that is processed from CF,the PM6:BTP-ClBr2 system demonstrates good efficiency of 16.28%processed from CB and the device based on PM6:BTP-4Cl achieves 16.33%using TMB as its solvent for the active layer.These are among the highest efficiencies for CB-and TMB-processed binary OSCs to date.The molecular packing and phase separation length scales of each combination depend strongly on the solvent,and the overall morphology is the result of the interplay between solvent evaporation(kinetics)and materials miscibility(thermodynamics).Different solvents are required to realize the optimal morphology due to the different miscibility between the donor and acceptor.Finally,17.36%efficiency was achieved by incorporating PC71BM for TMB-processed devices.Our result provides insights into the effect of processing solvent and shows the potential of realizing high-performance OSCs in conditions relevant for industrial fabrication.

MXenes and MXene-based composites for energy conversion and storage applications

MXenes have received extensive attention from scholars due to their unique layered structure,significant electrical conductivity,and excellent mechanical properties.In addition to their pristine forms,they could also be incorporated with other components for attaining hybrids and nanocomposites,accompanying with amplified functionalities.It has been widely used in lithium batteries,supercapacitors,electromagnetic shielding,tumor therapy,biosensors,photocatalysis,and other fields,and has shown great application potential in energy conversion and storage.The purpose of this article is to encyclopaedically overview the latest progress in synthesis and characterization of MXenes,while their potential applications in energy conversation such as water splitting and solar cells,as well as in energy storage such as Li-ion batteries,supercapacitors,and hydrogen energy will be comprehensively elaborated.Development opportunities and challenges are summarized.

Enhanced Photovoltage for Inverted Perovskite Solar Cells Using Delafossite CuCrO_(2) Hole Transport Material

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)has been widely adopted as hole transport material(HTM)in inverted perovskite solar cells(PSCs),due to high optical transparency,good mechanical flexibility,and high thermal stability;however,its acidity and hygroscopicity inevitably hamper the long-term stability of the PSCs and its energy level does not match well with perovskite materials with a relatively low open-circuit voltage.In this work,p-type delafossite CuCrO_(2)nanoparticles synthesized through hydrothermal method was employed as an alternative HTM for triple cation perovskite[(FAPbI_(3))_(0.87)(MAPbBr_(3))_(0.13)]_(0.92)(CsPbI_(3))_(0.08)(possessing better photovoltaic performance and stability than conventional CH3NH3PbI3)based inverted PSCs.The average open-circuit voltage of PSCs increases from 908 mV of the devices with PEDOT:PSS HTM to 1020 m V of the devices with CuCrO_(2)HTM.Ultraviolet photoemission spectroscopy demonstrates the energy band alignment between CuCrO_(2)and perovskite is better than that between PEDOT:PSS and perovskite,the electrochemical impedance spectroscopy indicates CuCrO_(2)-based PSCs exhibit larger recombination resistance and longer charge carrier lifetime than PEDOT:PSS-based PSCs,which contributes to the high VOCof CuCrO_(2)HTM-based PSCs.

Ultrafast charge transfer in dual graphene-WS_2 van der Waals quadrilayer heterostructures

Using dual graphene–WS2 quadrilayer heterostructures as an example, we find that the ultrafast transfer of electrons from WS2 to graphene takes place within 114 fs, and the Coulomb field of the charge can effectively affect the interlayer electron transfer. This effect illustrates that the charge transfer in such van der Waals heterostructures may be controlled by an externally applied electric field for promising applications in photoelectric devices.

S-scheme heterojunction photocatalysts for CO_(2) conversion: Design, characterization and categories

Photocatalytic CO_(2) conversion into valuable hydrocarbon fuels via solar light is a promising strategy to simul-taneously address energy shortage and environmental pollution.However,the photocatalytic CO_(2) reduction performance is too poor to be practically utilized due to the rapid recombination of photogenerated charge carriers.Constructing step-scheme(S-scheme)heterojunction photocatalysts can facilitate the charge separation and maximize the redox ability,thus remarkably enhancing the photocatalytic CO_(2) reduction activity.This review summarizes the progress of S-scheme heterojunction photocatalysts applied in the photocatalytic CO_(2) reduction reactions.Firstly,we introduce the fundamental design principles and characterization methods.The direct and indirect techniques to confirm the S-scheme charge transfer mechanism are disclosed.Secondly,we divide S-scheme composite photocatalyst into the following categories depending on their compositions:g-C_(3)N_(4)-based,metal-chalcogenide-based,TiO_(2)-based,bismuth-based,other metal oxide-based and other semiconductor-based S-scheme photocatalysts.The synergistic effect of the S-scheme charge transfer pathway as well as the unique intrinsic properties of semiconductor materials on the photocatalytic CO_(2) reduction performance is discussed in detail.Finally,concluding perspectives on the challenges and opportunities for the further exploration of highly efficient S-scheme photocatalysts in photocatalytic CO_(2) conversion are presented.

Harpoon-shaped topological photonic crystal for on-chip beam splitter

The advancement of integrated optical communication networks necessitates the deployment of on-chip beam splitters for efficient signal interconnections at network nodes.However,the pursuit of micron-scale beam splitting with large corners and reducing the device footprint to boost connection flexibility often results in phase mismatches.These mismatches,which stem from radiation modes and backward scattering,pose significant obstacles in creating highly integrated and interference-resistant connections.To address this,we introduce a solution based on the topological valley-contrasting state generated by photonic crystals with opposing valley Chern numbers,manifested in a harpoon-shaped structure designed to steer the splitting channels.This approach enables adiabatic mode field evolution over large corners,capitalizing on the robust phase modulation capabilities and topological protection provided by the subwavelength-scale valley-contrasting state.Our demonstration reveals that beam splitters with large corners of 60°,90°,and 120°exhibit insertion loss fluctuations below 2.7 dB while maintaining a minimal footprint of 8.8μm×8.8μm.As a practical demonstration,these devices facilitate three-channel signal connections,successfully transmitting quadrature phase shift keying signals at 3.66 Tbit/s with bit error rates below the forward error correction threshold,demonstrating performance comparable to that in defects scenarios.By harnessing the unidirectional excitation feature,we anticipate significant enhancements in the capabilities of signal distribution and connection networks through a daisy chain configuration.

Selective introduction of surface defects in anatase TiO2 nanosheets for highly efficient photocatalytic hydrogen generation

Defect engineering greatly enhances the cat-alytic activity of transition metal semiconductor photocat-alysts.Recently,localized surface defects engineering has been intensively researched,but it still remains challenges on how to tilt the balance to the controllable construction of surface defects rather than bulk ones.Here,we report a facile room-temperature solution processing strategy on(001)facet exposed anatase TiO_(2) nanosheets(ATO),in which localized defects are generated on the surface selectivity with high concentration.To achieve the aspect,lithium-ethylenediamine(Li-EDA)treatment is carried out on(001)facet exposed ATO under a mild condition.The optimized sample exhibits outstanding photocatalytic H_(2) production rates of 9.28 mmol·g^(-1)·h^(-1) with loading 0.5 wt%Pt as co-catalyst(AM 1.5),which is nearly 7.5 times higher than that of the pristine ATO.This defect engi-neering strategy of ATO photocatalyst will spark the ideas for the defects engineering and semiconductor photocata-lyst,which is with important application prospect in solar energy conversion,including hydrogen generation and carbon dioxide reduction.

Mode-locked fiber laser of 3.5 μm using a single-walled carbon nanotube saturable absorber mirror

We report on a mid-infrared fiber laser that uses a single-walled carbon nanotube saturable absorber mirror to realize the mode-locking operation.The laser generates 3.5 μm ultra-short pulses from an erbium-doped fluoride fiber by utilizing a dual-wavelength pumping scheme.Stable mode-locking is achieved at the 3.5 μm band with a repetition rate of 25.2 MHz.The maximum average power acquired from the laser in the mode-locking regime is 25 mW.The experimental results indicate that the carbon nanotube is an effective saturable absorber for mode-locking in the mid-infrared spectral region.

2D materials for conducting holes from grain boundaries in perovskite solar cells

Grain boundaries in organic-inorganic halide perovskite solar cells(PSCs)have been found to be detrimental to the photovoltaic performance of devices.Here,we develop a unique approach to overcome this problem by modifying the edges of perovskite grain boundaries with flakes of high-mobility two-dimensional(2D)materials via a convenient solution process.A synergistic effect between the 2D flakes and perovskite grain boundaries is observed for the first time,which can significantly enhance the performance of PSCs.We find that the 2D flakes can conduct holes from the grain boundaries to the hole transport layers in PSCs,thereby making hole channels in the grain boundaries of the devices.Hence,2D flakes with high carrier mobilities and short distances to grain boundaries can induce a more pronounced performance enhancement of the devices.This work presents a cost-effective strategy for improving the performance of PSCs by using high-mobility 2D materials.

Radiation-pressure-induced photoluminescence enhancement of all-inorganic perovskite CsPbBr3 quantum dots

Perovskite quantum dots(QDs) are of great interest due to their outstanding optoelectronic properties and tremendous application potential. Improving photoluminescence(PL) spectra in all-inorganic perovskite QDs is of great importance for performance enhancement. In this work, the PL quantum yield of the CsPbBr3 perovskite QDs is enhanced from 70% to 95% with increasing radiation pressure. Such enhancement is attributed to the increased binding energy of self-trapped excitons(STEs) upon radiation pressure, which is consistent with its blue-shifted PL and other characterization results. Furthermore, we study ultrafast absorption spectroscopy and find that the dynamics of relaxation from free excitons to STEs in radiation pressure CsPbBr3 QDs is ascribed to stronger electron–phonon coupling in the contracted octahedral structure. It is further demonstrated that radiation pressure can boost the PL efficiency and explore effectively the relationship between the structure and optical properties.

An overview on transparent ceramics with pyrochlore and fluorite structures

Transparent ceramics have potential applications in various areas,including aerospace,relativistic optics industries,medical cares and defense.Specifically,they can be used as laser gain media,armor windows,IR domes,solid-state phosphors,scintillators and electro-optical components.From crystal structure point of view,transparent ceramic materials should have high crystallographic symmetries(cubic,tetragonal and hexagonal),which have minimal birefringent effect.Currently,transparent ceramics are dominantly based on oxide materials,although there are also nonoxides,such as fluorides and nitrides(oxynitrides).Transparent ceramics with pyrochlore and fluorite structures have attracted much attention in recent years,whereas fluorides are not well described in the open literature.Therefore,this paper is aimed to deliver an overview on the progress of the two categories of transparent ceramics,from material processing and characterization point of view.

High-power, ultra-broadband supercontinuum source based upon 1/1.5 μm dual-band pumping

We experimentally demonstrate an all-fiber supercontinuum source that covers the spectral region ranging from visible to mid-infrared. The ultra-broadband supercontinuum is realized by pumping a cascaded photonic crystal fiber and a highly nonlinear fiber with a 1/1.5 μm dual-band pump source. A maximum output power of 9.01 W is achieved using the system,which is the highest power ever achieved from a supercontinuum source spanning from the visible to mid-infrared.