Urea electrooxidation-boosted hydrogen production on nitrogen-doped porous carbon nanorod-supported nickel phosphide nanoparticles

Urea electro-oxidation reaction(UEOR)-boosted water electrolysis can supplant the kinetics-restricted oxygen evolution reaction(OER)and provide an energy-saving method of hydrogen generation.However,low UEOR activity and the poisoning issue of the catalyst limit its practical application.Herein,a simple coordination reaction is used to synthesize the dimethylglyoxime-NiⅡcomplex(DMGNiⅡ),which efficiently serves as the initial precursor to synthesize nitrogen-doped carbon nanorodsupported nickel phosphide nanoparticle(Ni_(2)P/N-C)nanocomposites.The density functional theory calculations and electrochemical results reveal that nitrogen doping can weaken the adsorption of hydrogen and the generated CO_(2)resulting in an enhancement of hydrogen evolution reaction(HER)and UEOR activity.In addition,N-doping can also promote the generation of Ni,which can further promote the UEOR and HER performance.Concretely,the overpotential for the HER on Ni_(2)P/N-C-2h nanocomposites is only 201 m V at 10 mA cm,and the onset potential of the UEOR on NiP/NC-2h nanocomposites is only 1.34 V.Additionally,the Ni_(2)P/N-Cnanocomposites also show excellent long-term stability due to the introduction of nitrogen-doped carbon material.Consequently,the symmetric Ni_(2)P/N-C-2h||Ni_(2)P/N-C-2h urea electrolyzer requires 1.41 V of electrolysis voltage for urea electrolysis,which can be applied in energy-saving H_(2) production and environment purification.

Lithium Pre-cycling Induced Fast Kinetics of Commercial Sb2S3 Anode for Advanced Sodium Storage

Because of the abundant sodium resources and identical fundamental principles, sodium ion batteries(SIBs) are the state-of-the-art alternative for lithium ion batteries. However, the larger ionic radius of Na+causes sluggish reaction kinetics, which directly results in inferior electrochemical performance. In this work, the sodium storage properties of commercial bulk Sb2S3(CSS) were improved by a single lithiation/delithiation cycle obtaining the lithium pre-cycled Sb2S3(LSS). Quantitative analysis reveals that the sodiation/desodiation kinetics of CSS and LSS is mainly diffusion-controlled behavior and capacitive process, respectively. Thus, the reaction kinetics of LSS is promising, which exhibits improved initial coulombic efficiency, stable cycling performance, and high rate capability. In addition, a stable Licontaining solid electrolyte interphase film was formed during the lithiation process, which can prevent continuous consumption of electrolyte during the each sodiation process. These results demonstrate that prelithiation technique should be a potential strategy to promote practical application for SIBs.

Photocatalytic one-step synthesis of Ag nanoparticles without reducing agent and their catalytic redox performance supported on carbon

Synthesis of silver nanoparticles(Ag NPs) with state-of-the-art chemical or photo-reduction methods generally takes several steps and requires both reducing agents and stabilizers to obtain NPs with narrow size distribution.Herein, we report a novel method to synthesize Ag NPs rapidly in one step, achieving typical particle sizes in the range from 5 to 15 nm.The synthesis steps only involve three chemicals without any reducing agent: AgNO3 as precursor, polyvinylpyrrolidone(PVP) as stabilizer, and AgCl as photocatalyst.The Ag NPs were supported on carbon and showed excellent performance in thermal catalytic pnitrophenol reduction and nitrobenzene hydrogenation, and as electrocatalyst for the oxygen reduction reaction.

High-yield Production Techniques of High-quality and Early Maturity Hybrid Rice Xiangzaoyou 2017

Xiangzaoyou 2017 is an excellent early maturing variety bred from the combination of Neixiang 3A and the self-fertile restorer QN 2017 by Qiannan Institute of Agricultural Sciences of Guizhou Province,and it has been approved by the Guizhou Crop Variety Approval Committee( Approval No.: Qianshendao 2006001).In order to promote its application in production,the research on the seed production techniques of Xiangzaoyou 2017 was carried out,and the key technical points of high-yield seed production of Xiangzaoyou 2017 were put forward.

The Colored Oil Property Effect on Switching Behavior of Electro-Fluidic Display

The switchable oil layer driven by electrowetting gives visible color and light valve control, which is the basis of Electro-Fluidic Displays. The colored oil’s property is a key factor that influences the Electro-Fluidic Displays switching behavior. A purple oil was formulated by the oil-soluble purple dye in decane in this study. The dye molecule itself is nonpolar and it doesn’t dissolve in water. The concentration of colored oil influenced the oil/water interfacial tension and oil viscosity. The relationship of EFD switching behavior with oil/water interfacial tension, oil viscosity, and oil conductivity has been systematically investigated. The oil/water interfacial tension decreased with increasing oil concentration, in the meanwhile, the conductivity increased. Oil conductivity was one of the key factors that influenced the Electro-Fluidic Displays optical property. We found for the first time that at the lower oil concentration (2% - 10%), the interfacial tension plays a main role effect on the rupture voltage and response time, but as the conductivity of higher concentration of colored oil increased (at 20%), the rupture voltage-controlled both by conductivity and interfacial tension.

Photothermal phase change material microcapsules via cellulose nanocrystal and graphene oxide co-stabilized Pickering emulsion for solar and thermal energy storage

Phase change materials(PCMs)have attracted significant attention in thermal management due to their ability to store and release large amounts of heat during phase transitions.However,their widespread application is restricted by leakage issues.Encapsulating PCMs within polymeric microcapsules is a promising strategy to prevent leakage and increase heat transfer area with matrices.Moreover,photothermal PCM microcapsules are particularly desirable for solar energy storage.Herein,we fabricated photothermal PCM microcapsules with melamine-formaldehyde resin(MF)as shell using cellulose nanocrystal(CNC)and graphene oxide(GO)co-stabilized Pickering emulsion droplets as templates.CNC displays outstanding Pickering emulsifying ability and can facilitate the fixation of GO at the oil-water interface,resulting in a stable CNC/GO co-stabilized PCM Pickering emulsion.A polydopamine(PDA)layer was coated in-situ on the emulsion droplets via oxidization self-polymerization of dopamine.Meanwhile,GO was reduced to reduced GO(rGO)due to the reducing ability of PDA.The outmost MF shell of the PCM microcapsules was formed in-situ through the polymerization and crosslinking of MF prepolymer.The resulted PCM@CNC/rGO/PDA/MF microcapsules exhibit uniform sizes in the micrometer range,excellent leakage-proof performance,high phase change enthalpy(175.4 J g^(−1))and PCM encapsulation content(84.2%).Moreover,the presence of rGO and PDA endows PCM@CNC/rGO/PDA/MF microcapsules with outstanding photothermal conversion performance.The temperature of PCM@CNC/rGO/PDA/MF microcapsule slurries(15wt.%)can reach 73°C after light irradiation at 1 W cm^(−2).Therefore,photothermal PCM@CNC/rGO/PDA/MF microcapsules are promising for solar energy harvesting,thermal energy storage,and release in various applications,such as energy-efficient buildings and smart textiles.

Dynamic Control of Multiple Optical Patterns of Cholesteric Liquid Crystal Microdroplets by Light-Driven Molecular Motors

The key to high-level encryption and anti-counterfeiting techniques is the storage of multiple levels of distinct information that can be individually and precisely addressed by certain stimuli.This continues to be a formidable challenge as the concealed images or codes must be read with fast response and high resolution without cross-talk to the first layer of information.Here,we report a non-fluorescencebased strategy to establish responsive encryption labels taking advantage of solely tuning multiple optical patterns of cholesteric liquid crystal(CLC)microdroplets doped with light-driven molecular motors.The photo-triggered unidirectional rotation of the motor induced not only changes in the helical twist power value but the opposite helical orientation of the superstructure in CLCs as well,resulting in changes in both the structural color and the selective reflection of circularly polar light.The designed labels,which featured highly selective addressability of dual-level distinct information,good reversibility,and viewing angle-independence,were applied to build devices for daily practical use,demonstrating great potential in anti-counterfeiting technology and provide a versatile platform for enhanced data protection and encryption of authentic information.

Photo-responsive functional materials based on light-driven molecular motors

In the past two decades,the research and development of light-triggered molecular machines have mainly focused on developing molecular devices at the nanoscale.A key scientific issue in the field is how to amplify the controlled motion of molecules at the nanoscale along multiple length scales,such as the mesoscopic or the macroscopic scale,or in a more practical perspective,how to convert molecular motion into changes of properties of a macroscopic material.Light-driven molecular motors are able to perform repetitive unidirectional rotation upon irradiation,which offers unique opportunities for responsive macroscopic systems.With several reviews that focus on the design,synthesis and operation of the motors at the nanoscale,photo-responsive macroscopic materials based on light-driven molecular motors have not been comprehensively summarized.In the present review,we first discuss the strategy of confining absolute molecular rotation into relative rotation by grafting motors on surfaces.Secondly,examples of self-assemble motors in supramolecular polymers with high internal order are illustrated.Moreover,we will focus on building of motors in a covalently linked system such as polymeric gels and polymeric liquid crystals to generate complex responsive functions.Finally,a perspective toward future developments and opportunities is given.This review helps us getting a more and more clear picture and understanding on how complex movement can be programmed in light-responsive systems and how man-made adaptive materials can be invented,which can serve as an important guideline for further design of complex and advanced responsive materials.

Highly efficient nonuniform finite difference method for three-dimensional electrically stimulated liquid crystal photonic devices

Liquid crystal(LC)photonic devices have attracted intensive attention in recent decades,due to the merits of tunability,cost-effectiveness,and high efficiency.However,the precise and efficient simulation of large-scale three-dimensional electrically stimulated LC photonic devices remains challenging and resource consuming.Here we report a straightforward nonuniform finite difference method(NFDM)for efficiently simulating largescale LC photonic devices by employing a spatially nonuniform mesh grid.

HfO_(2)铁电薄膜基MFIS存储结构中的高κ介电晶籽层效应研究:铁电正交相生长和界面电荷注入抑制

HfO_(2)基材料铁电场效应晶体管(FeFET)商业化应用面临的一个重要挑战是其疲劳特性差.本文提出,在基于金属-铁电-绝缘层-半导体(MFIS)栅叠层结构的FeFET中研发合适的高κ界面晶籽层(SL)以大幅度提升其疲劳性能.我们在ZrO_(2),HfO_(2),(HfO_(2))0.75(Al_(2)O_(3))0.25(HAO)和Al_(2)O_(3)等典型的高κ介电SL上制备了Hf_(0.5)Zr_(0.5)O_(2)(HZO)铁电薄膜,系统研究了HZO薄膜的微观结构、铁电性及其MFIS器件的存储特性.首先,揭示了HZO薄膜中铁电正交相的形核和生长不仅受高κ介电SL表面能的影响,而且其微观结构对HZO中正交相的形成也起到重要作用.其次,澄清了高κ介电晶籽层对MFIS结构存储特性的影响,通过精确计算的MFIS结构的界面层电场,对MFIS结构的存储特性做出了合理解释.最后,基于HAO的高κSL的MFIS器件实现了铁电极化和界面电荷注入之间的合理优化,并且获得了较大铁电存储窗口(>1.0 V),出色的保持特性(>1.6×104s)和疲劳特性(>105).本文为未来解决HfO_(2)基Fe FET的疲劳问题提供了有价值的思路,为在介电SL上生长HfO_(2)铁电薄膜的其他高性能电子器件的开发提供了参考.

Mold-free self-assembled scalable microlens arrays with ultrasmooth surface and record-high resolution

Microlens arrays(MLAs)based on the selective wetting have opened new avenues for developing compact and miniaturized imaging and display techniques with ultrahigh resolution beyond the traditional bulky and volumetric optics.However,the selective wetting lenses explored so far have been constrained by the lack of precisely defined pattern for highly controllable wettability contrast,thus limiting the available droplet curvature and numerical aperture,which is a major challenge towards the practical high-performance MLAs.Here we report a mold-free and self-assembly approach of mass-production of scalable MLAs,which can also have ultrasmooth surface,ultrahigh resolution,and the large tuning range of the curvatures.The selective surface modification based on tunable oxygen plasma can facilitate the precise pattern with adjusted chemical contrast,thus creating large-scale microdroplets array with controlled curvature.The numerical aperture of the MLAs can be up to 0.26 and precisely tuned by adjusting the modification intensity or the droplet dose.The fabricated MLAs have high-quality surface with subnanometer roughness and allow for record-high resolution imaging up to equivalently 10,328 ppi,as we demonstrated.This study shows a cost-effective roadmap for mass-production of high-performance MLAs,which may find applications in the rapid proliferating integral imaging industry and high-resolution display.

具有大电导动态范围和多级电导态的铁电Hf_(0.5)Zr_(0.5)O_(2)栅控突触晶体管

得益于铁电材料的非易失性和快速擦写,铁电突触晶体管(FST)在神经形态计算应用中很有前景.然而,在低能耗下同时实现大电导动态范围(G_(max)/G_(min))和多级有效电导态仍是一个挑战.在此,本文首次提出了由铁电Hf_(0.5)Zr_(0.5)O_(2)(HZO)栅介质结合溶液处理的氧化铟(In_(2)O_(3))突触晶体管以解决上述问题.通过精细调控的铁电相以及对铁电体和铁电/半导体界面的电荷注入良好抑制,实现了优异的突触特性.在每个尖峰事件490 fJ的低能耗下,该FST成功模拟了高达101个有效电导状态的长时程增强/抑制(LTP/D),且具有大电导动态范围(G_(max)/G_(min)=32.2)和优异耐久性(>1000个循环).此外,模拟实现了96.5%的手写数字识别准确率,这是现有报道的FST的最高记录.这项工作为开发低成本、高性能和节能的铁电突触晶体管提供了一条新途径.

A reflective display based on the electro-microfluidic assembly of particles within suppressed water-in-oil droplet array

Reflective displays have stimulated considerable interest because of their friendly readability and low energy consumption.Herein,we develop a reflective display technique via an electro-microfluidic assembly of particles(eMAP)strategy whereby colored particles assemble into annular and planar structures inside a dyed water droplet to create"open"and"closed"states of a display pixel.Water-in-oil droplets are compressed within microwells to form a pixel array.The particles dispersed in droplets are driven by deformation-strengthened dielectrophoretic force to achieve fast and reversible motion and assemble into multiple structures.This eMAP based device can display designed information in three primary colors with≥170°viewing angle,~0.14 s switching time,and bistability with an optimized material system.This proposed technique demonstrates the basis of a high-performance and energy-saving reflective display,and the display speed and color quality could be further improved by structure and material optimization;exhibiting a potential reflective display technology.

Ultrathin Ni(OH)2 layer coupling with graphene for fast electron/ion transport in supercapacitor

Integration of fast electrochemical double-layer capacitance and large pseudocapacitance is a practical way to improve the overall capability of supercapacitor,yet remains challenging.Herein,an effective cyanogel synthetic strategy was demonstrated to prepare ultrathin Ni(OH)2 nanosheets coupling with conductive reduced graphene oxide(rGO)(rGO-Ni(OH)2)at ambient condition.Ultrathin Ni(OH)2 nanosheet with 3–4 layers of edge-sharing octahedral MO6 maximally exposes the active surface of Faradic reaction and promotes the ion diffusion,while the conductive rGO sheet boosts the electron transport during the reaction.Even at 30 A g−1,the optimal sample can deliver a specific capacitance of 1119.52 F g−1,and maintain 82.3%after 2000 cycles,demonstrating much higher electrochemical capability than bare Ni(OH)2 nanosheets.A maximum specific energy of 44.3 W h kg^−1(148.5 W kg^−1)is obtained,when assembled in a two-electrode system rGO-Ni(OH)2//rGO.This study provides an insight into efficient construction of two dimensional hybrid electrodes with high performance for the new-generation energy storage system.

Cell thickness dependence of electrically tunable infrared reflectors based on polymer stabilized cholesteric liquid crystals

We reported here the fabrication of the elec- trically tunable infrared （IR） reflectors based on the polymer stabilized cholesteric liquid crystal （PSCLC） with negative dielectric anisotropy. A systematic study of the influence of cell gap on the electrically tunable reflection bandwidth was performed. When a direct current （DC） electric field was ap- plied, the reflection bandwidth red shifted in the cells with small cell gap, whereas the bandwidth broadening was ob- served in the cells with large cell gap. It is therefore reasonable to deduct that the reflection is dictated by the pitch gradient steepness which strongly relies on the cell thickness. The re- sults reveal that for making PSCLC based IR reflector windows with electrically induced bandwidth broadening, a minimal cell gap thickness is required. The resulted IR reflectors pos- sess a short native switching time and long-term operation stability, and are potentially applicable as smart energy saving windows in buildings and automobiles.

Firm Characteristics and Chinese Stocks

This paper presents a comprehensive study on predicting the cross section of Chinese stock market returns with a large panel of 75 individual firm characteristics.We use not only the traditional Fama-MacBeth regression,but also the"big-data"econometric methods:principal component analysis(PCA),partial least squares(PLS),and forecast combination to extract information from all the 75 firm characteristics.These characteristics are important return predictors,with statistical and economic significance.Furthermore,firm characteristics that are related to trading frictions,momentum,and profitability are the most effective predictors of future stock returns in the Chinese stock market.

Tuning electroluminescence performance in Pr-doped piezoelectric bulk ceramics and composites

Alternating current electroluminescence(ACEL)shows great potential in lighting,display and intelligent skin.Herein,the ACEL properties of Pr3þ-doped Ba0$85Ca0$15Ti0$90Zr0$10O3 ceramic and its PDMS-based composite have been investigated.Intense red EL emission was obtained in the ceramic sample whereas blue EL emission of Pr3þwas observed for the first time in the composite counterpart.The red EL emission should be attributed to the impact of hot electrons driven by the large piezoelectric electric field.Owing to the cross-relaxations through the 4f5d levels and Pr-to-metal charge transfer state,the 3 PJ emissions were completely quenched,and thus leading to an enhancement in red emission.However,external E field induced a large local piezoelectric deformation of the ceramic particles embedded in the PDMS matrix,which in turn caused a bending of CB and then a downwards shift of the 4f5d levels from the CB.Hence the cross-relaxations were hindered,and the blue EL emission was observed in the composites.The results would attract attention of functional materials studies and expand our understanding of such facile structure and oxide EL devices to facilitate their use in integral part of flexible device systems.

Ferroelectricity in dopant-free HfO_(2) thin films prepared by pulsed laser deposition

As a high-k material,hafnium oxide(HfO_(2))has been used in gate dielectrics for decades.Since the discovery of polar phase in Si-doped HfO_(2) films,chemical doping has been widely demonstrated as an effective approach to stabilize the ferroelectric phase in HfO_(2) based thin films.However,the extra capping layer deposition,post-growth annealing and wake-up effect are usually required to arouse the ferroelectricity in HfO_(2) based thin films,resulting in the increase of complexity for sample synthesis and the impediment of device application.In this study,the ferroelectricity is observed in non-capped dopant-free HfO_(2) thin films prepared by pulsed laser deposition(PLD)without post-growth annealing.By adjusting the deposited temperature,oxygen pressure and thickness,the maximum polarization up to 14.7 m C/cm^(2) was obtained in 7.4 nm-thick film.The fraction of orthorhombic phase,concentrations of defects and size effects are considered as possible mechanisms for the influences of ferroelectric prop-erties.This study indicates that PLD is an effective technique to fabricate high-quality ferroelectric HfO_(2) thin films in the absence of chemical doping,capping layer deposition and post-growth annealing,which may boost the process of nonvolatile memory device application.

Inter-facet composition modulation of III-nitride nanowires over pyramid textured Si substrates by stationary molecular beam epitaxy

InGaN nanowires (NWs) are grown on pyramid textured Si substrates by stationary plasma-assisted molecular beam epitaxy (PA-MBE). The incidence angles of the highly directional source beams vary for different pyramid facets, inducing a distinct inter-facet modulation of the In content of the InGaN NWs, which is verified by spatial element distribution analysis. The resulting multi-wavelength emission is confirmed by photoluminescence (PL) and cathodoluminescence (CL). Pure GaN phase formation dominates on certain facets, which is attributed to extreme local growth conditions, such as low active N flux. On the same facets, InGaN NWs exhibit a morphology change close to the pyramid ridge, indicating inter-facet atom migration. This cross-talk effect due to inter-facet atom migration is verified by a decrease of the inter-facet In content modulation amplitude with shrinking pyramid size. A detailed analysis of the In content variation across individual pyramid facets and element distribution line profiles reveals that the cross-talk effect originates mainly from the inter-facet atom migration over the convex pyramid ridge facet boundaries rather than the concave base line facet boundaries. This is understood by first-principles calculations showing that the pyramid baseline facet boundary acts as an energy barrier for atom migration, which is much higher than that of the ridge facet boundary. The influence of the growth temperature on the inter-facet In content modulation is also presented. This work gives deep insight into the composition modulation for the realization of multi-color light-emitting devices based on the monolithic growth of InGaN NWs on pyramid textured Si substrates.

The electrochemical reforming of glycerol at Pd nanocrystals modified ultrathin NiO nanoplates hybrids:An efficient system for glyceraldehyde and hydrogen coproduction

The glycerol electro-oxidation reaction(GEOR)is a green and promising method for the glyceraldehyde production.In this work,Pd nanocrystals(Pd-NCs)modified ultrathin NiO nanoplates(NiO-uNPs)hybrids(Pd-NCs/NiO-uNPs)are successfully synthesized using successive cyanogel hydrolysis,chemical reduction,and calcination treatment methods.Various electrochemical measurements and physicochemical characterization results demonstrate that Pd-NCs/NiO-uNPs hybrids have excellent electrocatalytic performance for both GEOR and hydrogen evolution reaction(HER)in alkaline medium,which benefit from the large specific surface area,uniform distribution of Pd-NCs,and the modified electronic structure of Ni atoms.At Pd-NCs/NiO-uNPs hybrids,only 1.43 V is needed to obtain the current density of 100 mA∙cm^(−2) for GEOR,much lower than that for oxygen evolution reaction(1.82 V).In addition,Pd-NCs/NiO-uNPs hybrids exhibit better HER performance than commercial Pd/C electrocatalyst.As a result,the constructed Pd-NCs/NiO-uNPs||Pd-NCs/NiO-uNPs glycerol electrolyzer only requires 1.62 V electrolysis voltage to reach 10 mA∙cm^(−2) current density,showing an energy-efficient and economy-competitive synthesis for the coproduction of glyceraldehyde and hydrogen.