Convenient Design of Hollow Co3O4 Nanostructure on Carbon Cloth for Flexible Supercapacitors

We proposed a new approach to construct zeolitic imidazolate frameworks-67 (ZIF-67) powders directly on carbon cloth without any conductive agent and adhesion agent and the ZIF-67 nanoparticles on carbon cloth were successfully converted into hollow Co3O4 nanostructure via a facile calcination process. Compared with original ZIF-67 powders, the Co3O4@CC electrode materials had admirable specific capacitance of 1164.8 F·g^-1 at an area current density of 2.5 mA·cm^-2. Furthermore, the rate performance remained 42.4% of initial value when the current density was increased to 30 mA·cm^-2 and the specific capacitance maintained 93.4% of initial capacity after 5000 cycles at an area current density of 10 mA·cm^-2. This strategy may have potential prospect for the application of MOFs in the energy storage and conversion field.

Structural evolution of low-dimensional metal oxide semiconductors under external stress

Metal oxide semiconductors(MOSs) are attractive candidates as functional parts and connections in nanodevices.Upon spatial dimensionality reduction, the ubiquitous strain encountered in physical reality may result in structural instability and thus degrade the performance of MOS. Hence, the basic insight into the structural evolutions of low-dimensional MOS is a prerequisite for extensive applications, which unfortunately remains largely unexplored. Herein, we review the recent progress regarding the mechanical deformation mechanisms in MOSs, such as CuO and ZnO nanowires(NWs). We report the phase transformation of CuO NWs resulting from oxygen vacancy migration under compressive stress and the tensile strain-induced phase transition in ZnO NWs. Moreover, the influence of electron beam irradiation on interpreting the mechanical behaviors is discussed.

Extremely Anisotropic Thermoelectric Properties of SnSe Under Pressure

SnSe has attracted extensive attention due to its ultralow thermal conductivity and excellent thermoelectric properties.In this work,pressure-induced thermoelectric properties of Pnma SnSe are investigated via first-principles calculations.We uncover distinct energy isosurfaces topology transition of conduction band by applying pressure.The newly created conduction band valley caused by pressure has a distinct anisotropic shape compared to the old one.Inducing pressure can greatly enhance the anisotropy of electronic transport properties of the n-type Pnma SnSe.Furthermore,the lattice thermal conductivity also exhibits anisotropic behavior under pressure due to a special collaged phonon mode.The pressure-induced lattice thermal conductivity along the a-axis shows a slower growth trend than that along the b-axis and c-axis.The optimal ZT value of the n-type Pnma SnSe along the a-axis can reach 1.64 at room temperature.These results would be helpful for designing the Pnma SnSe-based materials for the potential thermoelectric and valleytronic applications.

Manipulating the electronic structure of Ni electrocatalyst through d‐p orbital hybridization induced by B‐doping for efficient alkaline hydrogen oxidation reaction

Developing highly efficient platinum‐group‐metal‐free electrocatalysts towards hydrogen oxidation reaction(HOR)under alkaline electrolyte is critical for the development of alkaline exchange member fuel cells.Herein,we reported the synthesis of boron doped Ni electrocatalyst(B‐Ni/C)and its remarkable alkaline HOR performance,with a 10‐fold mass activity enhancement compared with that of undoped Ni catalyst.Experimental results and density functional theory calculations indicate the d‐p hybridization between the p orbital of B and the d orbital of Ni via B‐doping could lead to promoted OH adsorption and optimized hydrogen binding energy on Ni surface,which together with the reduced formation energy of water species,contributes to the enhanced HOR performance under alkaline electrolyte.

A Single-Sized Metasurface for Image Steganography and Multi-Key Information Encryption

With the escalating flow of information and digital communication,information security has become an increasingly important issue.Traditional cryptographic methods are being threatened by advancing progress in computing,while physical encryption methods are favored as a viable and compelling avenue.Metasurfaces,which are known for their extraordinary ability to manipulate optical parameters at the nanoscale,exhibit significant potential for the revolution of optical devices,making them a highly promising candidate for optical encryption applications.Here,a single-sized metasurface with four independent channels is proposed for conducting steganography and multi-key information encryption.More specifically,plaintext is transformed into a ciphertext image,which is encoded into a metasurface,while the decryption key is discretely integrated into another channel within the same metasurface.Two different keys for steganographic image unveiling are also encoded into the metasurface and can be retrieved with different channels and spatial positions.This distributed multi-key encryption approach can enhance security,while strategically distributing images across distinct spatial zones serves as an additional measure to reduce the risk of information leakage.This minimalist designed metasurface,with its advantages of high information density and robust security,holds promise across applications including portable encryption,high-camouflaged image display,and high-density optical storage.

Wave height measurement in the Taiwan Strait with a portable high frequency surface wave radar

As an important equipment for sea state remote sensing, high frequency surface wave radar （HFSWR） has received more and more attention. The conventional method for wave height inversion is based on the ratio of the integration of the second-order spectral continuum to that of the first-order region, where the strong external noise and the incorrect delineation of the first- and second-order Doppler spectral regions due to spectral aliasing are two major sources of errors in the wave height. To account for these factors, two more indices are introduced to the wave height estimation, i.e., the ratio of the maximum power of the second-or- der continuum to that of the Bragg spectral region （RSCB） and the ratio of the power of the second harmonic peak to that of the Bragg peak （RSHB）. Both indices also have a strong correlation with the underlying wave height. On the basis of all these indices an empirical model is proposed to estimate the wave height. This method has been used in a three-months long experiment of the ocean state measuring and analyzing ra- dar, type S （OSMAR-S）, which is a portable HFSWR with compact cross-loop/monopole receive antennas developed by Wuhan University since 2006. During the experiment in the Taiwan Strait, the significant wave height varied from 0 to 5 m. The significant wave heights estimated by the OSMAR-S correlate well with the data provided by the Oceanweather Inc. for comparison, with a correlation coefficient of 0.74 and a root mean square error （RMSE） of 0.77 m. The proposed method has made an effective improvement to the wave height estimation and thus a further step toward operational use of the OSMAR-S in the wave height extraction.

Recent advances in alkaline hydrogen oxidation reaction

The development of highly efficient electrocatalysts toward hydrogen oxidation reaction(HOR)under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cells(AEMFCs).However,the HOR kinetics in alkaline is two to three orders of magnitude slower than that in acid.More critically,fundamental understanding of the sluggish kinetics derived from the p H effect is still debatable.In this review,the recent development of understanding HOR mechanism and rational design of advanced HOR electrocatalysts are summarized.First,recent advances in the theories focusing on fundamental understandings of HOR under alkaline electrolyte are comprehensively discussed.Then,from the aspect of intermediates binding energy,optimizing hydrogen binding energy(HBE)and increasing hydroxyl binding energy(OHBE),the strategies for designing efficient alkaline HOR catalysts are summarized.At last,perspectives for the future research on alkaline HOR are pointed out.

Nitridation-induced metal-organic framework nanosheet for enhanced water oxidation electrocatalysis

We report the synthesis of nitridation-induced NiFe-MOF through post-synthetic functionalization of terminal ligand in NiFe-MOF nanosheet.We directly identify the key factor of amino ligand in N-NiFe-MOF for boosting the OER performance through combining single X-ray crystallographic characterization and in-situ Raman tracking,as well as ex-situ spectroscopy analysis.Density functional theory(DFT)calculations and experime ntal results indicate irreversible phase rec on structio n from amino ligand oxidation prior to OER could lead to the optimized ΔG_(-O),resulting in the remarkable OER performance with an overpotential of 258 mV to obtain the current density of 100 mA cm^(-2) in 1.0 M KOH solution.Our work will provide new strategy for rational designing advanced MOF-based OER electrocatalysts.

Wave Extraction with Portable High-Frequency Surface Wave Radar OSMAR-S

High frequency surface wave radar(HFSWR) has now gained more and more attention in real-time monitoring of sea surface states such as current, waves and wind. Normally a small-aperture antenna array is preferred to a large-aperture one due to the easiness and low cost to set up. However, the large beam-width and the corresponding incorrect division of the first- and second-order Doppler spectral regions often lead to big errors in wave height and period estimations. Therefore, for the HFSWR with a compact cross-loop/monopole antenna(CMA), a new algorithm involving improved beam-forming(BF) and spectral division techniques is proposed. On one hand, the cross-spectrum of the output sequence by the conventional beam-forming(CBF) with all the three elements and the output with only the two loops is used in place of the CMA output self-spectrum to achieve a decreased beam-width; on the other hand, the better null seeking process is included to improve the division accuracy of the first- and second-order regions. The algorithm is used to reprocess the data collected by the portable HFSWR OSMAR-S during the Sailing Competition of the 16 th Asian Games held in Shanwei in November 2010, and the improvements of both the correlation coefficients and root-mean-square(RMS) errors between the wave height and period estimations and in situ buoy measurements are obvious. The algorithm has greatly enhanced the capabilities of OSMAR-S in wave measurements.

Organic photodetectors with non-fullerene acceptors

During last decade,organic photovoltaics experienced an exciting renaissance[1-5],mainly benefiting from the development of non-fullerene acceptors(NFAs),which boosted the power conversion efficiency to-20%[6,7].Along with the unprecedented success of organic solar cells,non-fullerene acceptors also find other optoelectronic applications.In particular,high-performance organic photodetectors(OPDs)[8,9]based on non-fullerene acceptors have been reported.

Stereodivergent synthesis ofα-fluoroα-azaarylγ-butyrolactones via cooperative copper and iridium catalysis

The development of stereodivergent synthetic methods to access all four stereoisomers of biologically importantα-fluoroγ-butyrolactones containing vicinal stereocenters is of great importance and poses a formidable challenge owing to ring strain and steric hindrance.Herein,a novel asymmetric[3+2]annulation ofα-fluoroα-azaaryl acetates with vinylethylene carbonate was successfully developed through Cu/Ir-catalyzed cascade allylic alkylation/lactonization,affording a variety of enantioenrichedα-fluoroγ-butyrolactones bearing vicinal stereogenic centers with high reaction efficiency and excellent levels of both stereoselectivity and regioselectivity(up to 98%yield,generally>20:1 dr and>99%ee).Notably,all four stereoisomers of these pharmaceutically valuable molecules could be accessed individually via simple permutations of two enantiomeric catalysts.In addition,other azaaryl acetates bearingα-methyl,α-chlorine orα-phenyl group were tolerated well in this transformation.Reaction mechanistic investigations were conducted to explore the process of this bimetallic catalysis based on the results of reaction intermediates,isotopic labelling experiments,and kinetic studies.

NiRh nanoparticles supported on nitrogen-doped porous carbon as highly efficient catalysts for dehydrogenation of hydrazine in alkaline solution

Well-dispersed bimetallic NiRh nanoparticles （NPs） with different compositions supported on nitrogen-doped porous carbon （NPC） derived from metal-organic frameworks （ZIF-8） were synthesized through a co-reduction method. The NPC-900 supported NiRh catalyst exhibits the highest catalytic activity and 100% hydrogen selectivity toward hydrogen generation from hydrazine. These properties might be attributed to the high surface area and high graphitization of the NPC. This strategy may open up a new avenue for designing high-performance catalysts by utilizing NPC as a support to anchor active metal NPs for additional applications.

Discrepant roles of adsorbed OH^* species on IrWOx for boosting alkaline hydrogen electrocatalysis

Improving the slow kinetics of alkaline hydrogen electrode reactions, involving hydrogen oxidation and evolution reactions(HOR/HER) is highly desirable for accelerating the commercialization of alkaline exchange membrane-based fuel cells(AEMFCs) and water electrolyzers(AEMWEs). However, fundamental understanding of the mechanism for HOR/HER catalysis under alkaline media is still debatable. Here we develop an amorphous tungsten oxide clusters modified iridium-tungsten nanocrystallines(Ir WOx)which exhibited by far the highest exchange current density and mass activity, about three times higher than the commercial Pt/C toward alkaline HOR/HER. Density functional theory(DFT) calculations reveal the WOxclusters act as a pivotal role to boost reversible hydrogen electrode reactions in alkaline condition but via different mechanisms, which are, hydrogen binding energy(HBE) mechanism for HOR and bifunctional mechanism for HER. This work is expected to promote our fundamental understanding about the alkaline HOR/HER catalysis and provide a new avenue for rational design of highly efficient electrocatalysts toward HOR/HER under alkaline electrolytes.

Enhanced catalytic activity of Ru through N modification toward alkaline hydrogen electrocatalysis

Exploring highly efficient electrocatalysts and understanding the reaction mechanisms for hydrogen electrocatalysis,including hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline media are conducive to the conversion of hydrogen energy.Herein,we reported a new strategy to boost the HER/HOR performances of ruthenium (Ru) nanoparticles through nitrogen (N) modification.The obtained N-Ru/C exhibit remarkable catalytic performance,with normalized HOR exchange current density and mass activity of 0.56 m A/cm^(2)and 0.54 m A/μg,respectively,about 4 and 4.5 times higher than those of Ru/C,and even twofold enhancement compared to commercial Pt/C.Moreover,at the overpotential of 50 m V,the normalized HER current density of N-Ru/C is 5.5 times higher than that of Ru/C.Experimental and density functional theory (DFT) results verify the electronic regulation of Ru after N incorporation,resulting in the optimized hydrogen adsorption Gibbs free energy (ΔG_(H*)) and hence enhancing the HOR/HER performance.

Ruthenium deposited on MCM-41 as efficient catalyst for hydrolytic dehydrogenation of ammonia borane and methylamine borane

Ultrafine Ru nanoparticles are successfully deposited on MCM-41 by using a simple liquid impregnation- reduction method, and further investigated for catalytic hydrolysis of ammonia borane and methylamine borane. Among all the catalysts tested, 1.12wt% Ru/MCM-41 exhibits the highest catalytic activity, with turnover frequency value of 288 min^-1

Molybdenum-induced tuning 3d-orbital electron filling degree of CoSe_(2) for alkaline hydrogen and oxygen evolution reactions

The development of high-performance non-precious metal-based robust bifunctional electrocatalyst for both hydrogen evolution reaction(HER) and oxygen evolution reactions(OER) in alkaline media is essential for the electrochemical overall water splitting technologies. Herein, we demonstrate that the HER/OER performance of Co Se_(2)can be significantly enhanced by tuning the 3d-orbital electron filling degree through Mo doping. Both density functional theory(DFT) calculations and experimental results imply that the doping of Mo with higher proportion of the unoccupied d-orbital(P_(un)) could not only serve as the active center for water adsorption to enhance the water molecule activation, but also modulate the electronic structures of Co metal center leading to the optimized adsorption strength of*H. As expected, the obtained Mo-Co Se_(2)exhibits a remarkable bifunctional performance with overpotential of only 85 m V for HER and 245 m V for OER to achieve the current density of 10 m A/cm^(2)in alkaline media.This work will provide a valuable insight to design highly efficient bifunctional electrocatalyst towards HER and OER.

Bionic surface design of cemented carbide drill bit

The development of a high-performance cemented carbide drill bit is of great significance to the reduction of rock drilling-cost. The non-smooth features of a biological surface provide an insight into how they can obtain low friction and good wear resistance with evolving surface morphology. By analyzing the mechanism of the surface of a dung beetle for reducing soil wear and adherence, we design a cemented carbide drill bit with a bionic surface, which is expected to have superior anti-wearing and anti-sticking properties for drilling the soft coal seam. Inspired from the characteristics of the head and pronotum surface of the dung beetle, optimized non-smooth surface of the drill bit was constructed. The working performance of this innovative drill was experimentally tested. With comparative experiments under the identical drilling conditions, the wear rates, drilling times of conventional drills and bionic drills were measured. Compared with the conventional counterpart, the drill designed exhibits better performance in reducing wear and sticking drilling-breaks, therefore achieving higher levels of efficiency. The diameter of the dome and pit on the bit surface is in the range of 0.8–1.2 mm, and the bionic drill bits could get better performance with preferable drilling speeds and wear rates.

Ni_(3)N Modified MOF Heterostructure with Tailored Electronic Structure for Efficient Overall Water Splitting

Exploring bifunctional electrocatalysts with high-efficiency and stability toward overall water splitting is desirable for sustainable energy technologies,yet challenging.Herein,we report the construction of Ni_(3)N on the surface of Ni-MOF-74 through an in-situ nitriding process.The obtained Ni-MOF-74/Ni_(3)N exhibits remarkable HER activity with an overpotential of 73 mV to deliver 10 mA cm^(-2).Theoretical calculations and experimental study demonstrate the electron transport between Ni_(3)N and Ni-MOF-74,leading to the improved H_(2)O adsorption,optimized hydrogen adsorption,and increased H_(ad)diffusion,which contributes to the enhanced HER performance.Besides,the obtained Ni-MOF-74/Ni_(3)N also possesses outstanding activity toward OER and overall water splitting.

Effects of twin orientation and twin boundary spacing on the plastic deformation behaviors in Ni nanowires

Spreading twins throughout nano metals has been proved to effectively mediate the mechanical behaviors in face-centered-cubic(fcc)metals.However,the experimental investigation concerning the roles of twin boundary(TB)during deformation is rarely reported.Here,with the joint efforts of in-situ nanomechani-cal testing and theoretical studies,we provide a systematic investigation regarding the effects of TB orien-tation(θ,the angle between tensile loading direction and the normal of TB)and spacing on deformation mechanisms in Ni nanowires(NWs).As compared with single-crystalline counterparts,it is found that nano-twinned(nt)NWs withθ∼0°exhibit limited ductility,whereas TB can serve as an effective block-age to the dislocation propagation.In contrast,in nt NWs withθ∼20°and 55°,TB migration/detwinning induced by TB-dislocation reaction or partial dislocation movement dominates the plasticity,which con-tributes to enhanced NW ductility.Regarding nt NWs withθ∼90°,dislocations are found to be able to transmit through the TBs,suggesting the limited effect of TB on the NW stretchability.Furthermore,de-creasing TB spacing(λ)can facilitate the detwinning process and thus greatly enhance the ductility of NW withθ∼55°.This study uncovers the distinct roles that TB can play during mechanical deforma-tions in fcc NWs and provides an atomistic view into the direct linkage between macroscopic mechanical properties and microscopic deformation modes.

Stereodivergent Synthesis of Carbocyclic Quaternary α-Amino Acid Derivatives Containing Two Contiguous Stereocenters

A novel approach to stereodivergent synthesis of carbocyclicα-quaternary amino acid derivatives,bearing two contiguous stereocenters,is proposed through sequential dual Cu/Ir-catalyzed asymmetric allylation and ring-closing metathesis.A variety of five and six-membered carbocyclicα-quaternary amino acid derivatives could be readily achieved in good to high yields with exclusive regioselectivities,excellent diastereoselectivities(13:1->20:1 dr)and enantioselectivities(generally>99%ee).Of particular note is that the current protocol is also a versatile synthetic tool for the stereodivergent construction of the challenging seven and eight-membered carbocyclicα-amino acid derivatives.All four stereoisomers of these important molecules could be precisely synthesized through the permutation of chiral Cu/Ir catalytic system.The power of this strategy has been demonstrated for the facile access to some biologically active chiral molecules,such as spiro-hydantoins.