Palladium nanoclusters immobilized on defective nanodiamond-graphene core-shell supports for semihydrogenation of phenylacetylene

We report a nanocarbon material with nanodiamond(ND) core and graphene shell(ND@G) as a support for Pd nanocatalysts. The designed catalyst performed good selectivity of styrene(85.2%) at full conversion of phenylacetylene and superior stability under mild conditions. Supported Pd catalysts are characterized by means of high resolution transmission electron microscopy(HRTEM), Raman, X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and H2 temperature-programmed reduction(H2-TPR).The results clearly show that formation of the strong metal-support interaction(SMSI) between Pd nanoclusters and the defective graphene shell helpfully modifies the selectivity and stability of the Pd-based catalysts.

A MoS_2 nanocatalyst with surface-enriched active sites for the heterogeneous transfer hydrogenation of nitroarenes

A highly efficient and reusable plane‐curved and interlayer‐expanded MoS2nanocatalyst with increased exposure of active sites was prepared.The catalyst was used for the heterogeneous hydrogen transfer reaction of nitroarenes with hydrazine monohydrate as a reductant under mild reaction conditions without pressure and base,which was different from other hydrogen transfer systems that require the presence of a base(e.g.,propan‐2‐ol/KOH).The sandwiching of carbon between the MoS2nanosheets increased the distance between the layers of MoS2and exposed more Mo sites,resulting in superior catalytic performance compared with that of bulk MoS2catalyst.The active hydrogen(H*)generated from N2H4could directly transfer to the–NO2groups of nitrobenzene to form aniline followed by N2emission,which was confirmed by detecting the gas emission with mass spectrometry during the decomposition of hydrazine or the co‐existence of nitrobenzene and hydrazine.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Phosphate modified carbon nanotubes for oxidative dehydrogenation of n-butane

Catalytic performance of phosphate-modified carbon nanotube（PoCNT） catalysts for oxidative dehydrogenation（ODH） of n-butane has been systematically investigated. The Po CNT catalysts are characterized by SEM, TEM, XPS and TG techniques. We set the products selectivity as a function of butane conversion over various phosphate loading, and it is found that the PoCNT catalyst with the 0.8% phosphate weight loading（0.8PoCNT） exhibits the best catalytic performance. When the phosphate loading is higher than 0.8 wt%, the difference of catalytic activity among the PoCNT catalysts is neglectable. Consequently, the ODH of n-butane over the 0.8PoCNT catalyst is particularly discussed via changing the reaction conditions including reaction temperatures, residence time and n-butane/O;ratios. The interacting mechanism of phosphate with the oxygen functional groups on the CNT surface is also proposed.

Boron nitride for enhanced oxidative dehydrogenation of ethylbenzene

It is demonstrated experimentally and confirmed theoretically that highly defective boron nitride showed outstanding performance for oxidative dehydrogenation of ethylbenzene.The catalyst is derived from carbon-doped hexagonal boron nitride nanosheets synthesized via a two-step reaction when participating the oxidative dehydrogenation reaction.The first step yields a polymeric precursor with the atomic positions of B,C,N relatively constrained,which is conducive for the formation of carbon atomic clusters uniformly dispersed throughout the BN framework.During the oxidative dehydrogenation of ethylbenzene to styrene,the nanoscale carbon clusters are removed and highly defective boron nitride(D-BN)is obtained,exposing boron-rich zigzag edges of BN that act as the catalytic sites.The catalytic performance of D-BN is therefore remarkably better than un-doped h-BN.Our results indicate that dispersed C-doping in h-BN is highly effective in terms of defect formation and resultant enhanced activity in oxidative dehydrogenation reactions.

Parameter Identification and Application of Slippage Kinematics for Tracked Mobile Robots

A new parameter identification method is proposed to solve the slippage problem when tracked mobile robots execute turning motions.Such motion is divided into two states in this paper:pivot turning and coupled turning between angular velocity and linear velocity.In the processing of pivot turning,the slippage parameters could be obtained by measuring the end point in a square path.In the process of coupled turning,the slippage parameters could be calculated by measuring the perimeter of a circular path and the linear distance between the start and end points.The identification results showed that slippage parameters were affected by velocity.Therefore,a fuzzy rule base was established with the basis on the identification data,and a fuzzy controller was applied to motion control and dead reckoning.This method effectively compensated for errors resulting in unequal tension between the left and right tracks,structural dimensions and slippage.The results demonstrated that the accuracy of robot positioning and control could be substantially improved on a rigid floor.

Protective Effects of Flavonoids from Pteridium aquilinum on CCl_(4)-induced Acute Liver Injury in Mice

[Objectives]To explore the protective effects of flavonoids from Pteridium aquilinum(PAFL)on carbon tetracholoride(CCl_(4))-induced acute liver injury in mice and its potential mechanism.[Methods]All mice were randomly divided into four groups(n=10 in each),normal group,CCl_(4)group,CCl_(4)+PAFL groups[treated with PAFL(50 or 200 mg/kg)].Animal treatment was continued for 7 consecutive days.The blood was collected after injection of CCl_(4)for 24 h,and the liver tissue was removed from the mice and stored at-80℃.[Results]The PAFL(50 and 200 mg/kg)significantly inhibited the increase of aspartate aminotransferase(AST)and alanine aminotransferase(ALT)levels in serum caused by CCl_(4)treatment.PAFL administration not only increased the activity of antioxidant enzymes superoxide dismutase(SOD),Glutathione(GSH)and catalase(CAT)in mice,but also reduced the level of malondialdehyde(MDA).Meanwhile,PAFL administration decreased the expression of nuclear factor-kappa B(NF-κB)and Cyclooxygenase-2(COX-2)proteins and inhibited the release of pro-inflammatory factors tumor necrosis factor-α(TNF-α),interleukin-1β(IL-1β)and interleukin 6(IL-6).In addition,PAFL(200 mg/kg)treatment down-regulated extracellular regulated protein kinases(ERK)and c-Jun N-terminal kinase(JNK)protein levels in liver tissue.[Conclusions]These findings clearly indicate that the protective effects of PAFL on CCl_(4)-induced acute liver injury is related to its antioxidant and anti-inflammatory activity,which may be mediated by NF-κB and MAPKs signaling pathways.

Discussion on the Feasibility of nudge in Education

This paper first introduces the definition of nudge,the history of nudge and the advantages of nudge.This concept means a relatively subtle policy shift that encourages people to make decisions that are in their broad self-interest.It relies on insights from behavioral science,and when used ethically,it can be very helpful.Subsequently,the research results of the nudge method in public decision-making fields such as health and environmental protection are listed,inferring the feasibility of nudge method in the field of education,especially learners’specific behavior decision.Then according to the classification of the nudge method by the decision-making system,the research on nudge used in the education field is enumerated.It demonstrates that nudge still has a lot of room for expansion in the field of education.

A survey of Higher Vocational Students' upward Comparative Parenting

This study is aim at investigate the current situation of higher vocational students receiving upward comparative parenting and the differences in upward comparative parenting among higher vocational college students with different demographic variables.By using the self-designed upward comparative parenting questionnaire to survey 1075 higher vocational college students,the results show that:In general,higher vocational college students receive the highest frequency of upward Comparative Parenting(2.95±1.57)on the level of learning diligence,and the frequency of upward Comparative Parenting(2.62±1.27)for male higher vocational students is higher than that for female students(2.39±1.17).The subjects from urban areas(2.56±1.29)were significantly higher than those from rural areas(2.39±1.14).Conclusion:upward comparat ive parenting is a common phenomenon among higher vocational college students in China.

Hydrolysis mechanism of YbB_(2)C_(2)and the microstructure of the carbon derived from the hydrolysis reaction

Carbide-derived carbon(CDC)materials have gained great attention due to the excellent properties for various potential applications.Here,graphite crystal is formed during a room-temperature hydrolysis pro-cess of layered compound YbB_(2)C_(2).The formation mechanism can be demonstrated by a YbB_(2)C_(2)molecular cell:Yb^(3+)acts as a cathode where H_(2)O molecule is reduced to H atom and OH^(−)ion,while(B_(2)C_(2))^(3−)acts as an anode where OH−ion is oxidized to O atom.Then,YbB_(2)C_(2)molecular cell begins to disintegrate,i.e.,Yb^(3+)ion,B and C atoms dissociate from the molecular cell.The as-produced C atoms combine to form graphite crystal.The initial graphite crystal is a cabbage-like microsphere,and then it gradually disintegrates and transforms into layered graphite.In addition,YbB_(6),Yb_(3)(OH)_(3)n(BO_(3))_((3-n))sol,hydrogen,hydrocarbons,and carbon oxides form simultaneously.Our method provides a general and inexpensive route to obtain carbide-derived graphite crystal.

考虑三维流动效应的自然层流短舱压力分布反设计

针对三维流动效应下非轴对称自然层流(NLF)短舱设计困难的问题,发展了一种基于机器学习技术的压力分布反设计方法。短舱参数化建模使用自由曲面变形技术(FFD),通过求解RANS方程和基于SST(Shear Stress Transport)湍流模型的■转捩模型实现自然转捩预测,利用生成拓扑映射(GTM)模型建立短舱外形及其压力分布数据集与低维隐空间变量的映射关系,全局优化算法在隐空间高效寻优,获得与目标压力分布匹配的短舱气动外形,实现自然层流短舱的反设计。GTM模型建立了数据集在高低维度间的高精度映射关系,优化设计过程中无需反复调用CFD求解器,设计效率大幅提升。利用该方法对通气短舱进行三维优化设计,设计所得非轴对称短舱外表面的自然层流区最大长度达当地弦长的40.5%,比优化前延长了12.2%,验证了该方法在考虑三维流动效应下NLF短舱的优化设计能力。

Dynamic compression behavior of TiZrNbV refractory high-entropy alloys upon ultrahigh strain rate loading

In this study,the dynamic compressive response behavior of a body-centered cubic(BCC)single-phase TiZrNbV refractory high-entropy alloy(RHEA)was investigated under impact at speeds of 313-1584 m s^(-1)using two-stage,gas-gun-driven,high-speed plate-impact experiments;recovery sample analysis;and theoretical calculations.The strain rate and pressure were approximately 10^(7) s^(−1) and 5.07-29.37 GPa,respectively.The results showed that the TiZrNbV RHEA had a Hugoniot elastic limit of 4.12-5.86 GPa and a spall strength of 1.84-2.03 GPa.The initial yield strength of the alloy showed a strong strain-rate dependence and could be described by the modified Zerilli-Armstrong model,while the phonon-damping effect was the main reason for its high strain-rate sensitivity.Microstructural analysis showed that the dynamic deformation of the TiZrNbV RHEA was controlled by the dislocation slip,dislocation proliferation,intersection of the deformation bands,and grain refinement.The analysis also showed that the intergranular,transgranular,and mixed-type cracks dominated the spall failure of the material.The dynamic Hall-Petch effect and pinning from the lattice distortion led to high dynamic yield strength.The critical strain rate for the phonon drag effect was positively related to the relative atomic mass and local strain field of the metals.Within the experimental loading range,the RHEA showed good structural stability,and simultaneously,the theoretical calculation method for the equation of state based on a cold-energy mixture could accurately predict its shock-response behavior.The valence-electron concentration(VEC)had a direct effect on the shock-compression properties of the HEAs;higher VEC implied more difficulty in compressing the HEAs.The findings of this study provide insights into understanding the mechanical response characteristics of RHEAs under extreme conditions such as high-speed impact and ultrahigh strain-rate loading.

Determining the contribution of Mo single atoms components in MoO_(2)nanocatalyst in transfer hydrogenation

Nanocatalysts are likely to contain undetected single-atom components,which may have been ignored but have significant effect in catalytic reactions.Herein,we report a catalyst composed of Mo single atoms(SAs)and MoO_(2)nanoparticles(NPs)(MoSAs-MoO_(2)@NC),which is an exact model to understand how the SAs contribute to the nanocatalyst.Both experimental results and the density functional theory calculations reveal that Mo SAs on nitrogen-doped carbon provides the reaction zone for nitro reduction,while MoO_(2)is the active site for decomposing hydrazine hydrate to produce H*.Thanks to the synergy between Mo SAs and MoO_(2)NPs,this catalyst exhibits noble metal-like catalytic activity(100%conversion at 4 min)for the dechlorination-proof transfer hydrogenation.Additionally,the hydrogen migration on the catalyst is verified by the electrochemical tests in the absence of a hydrogen source.This work provides a model for further study on the coexistence of single atoms in nanoparticle catalysts.

Atomically Dispersed Metals on Nanodiamond-Derived Hybrid Materials for Heterogeneous Catalysis

CONSPECTUS:Supported metal catalyst,has been one of the most important systems in the field of heterogeneous catalysis.The great complexity of both the compositions and structures of such supported metal catalysts provides a great degree of freedom for tuning their catalytic properties,which has essentially triggered the explosive growth in research on design and control active metals’surface structures for decades.An ideal metal catalyst theoretically features maximum active sites and optimal intrinsic reactivity to facilitate a desired chemical reaction.Inspired by the catalytic concepts brought by natural enzymes and homogeneous catalysis,the fabrication of heterogeneous catalysts with atomically dispersed metal atoms has attracted much attention and been extensively explored in recent years.Atomically dispersed metal catalysts(ADMCs)including single-atom catalyst(SACs)and fully exposed cluster catalyst(FECCs),as shining stars in heterogeneous catalysts have recently drawn much attention.The advantages of ADMCs mainly include the following three aspects:(1)the fully exposed active metal atoms can realize the utmost atomic utilization efficiency and reduce the cost of catalysts;(2)the geometric and electronic structure can be effectively regulated by altering the coordination environments of metal atoms and then further tuning the catalytic performance in terms of activity,selectivity,and stability;(3)the precisely designed structures provide a promising platform for digging the structure−performance relationships of active sites with the assistance of theoretical calculations.Owing to these advantages,ADMCs have been used in thermal-catalysis,electrocatalysis,photocatalysis,etc.until now.In this Account,a summary of recent progress regarding ADMCs for heterogeneous thermal catalysis in our group will be presented from the following aspects.First,an overview of great opportunities brought by nanodiamond and its derivatives as substrates for anchoring atomically dispersed metals(ADMs)and tailoring their structures.Next,our recent progress in achieving desirable catalytic performance,including activity,selectivity,and stability over nanodiamond−graphene(ND@G)supported ADMCs will be introduced in detail.Finally,a brief outlook regarding the development directions for ADMCs by discussing current challenges and opportunities will be proposed.It is hoped that this Account can inspire the development of the rational design and various application of ADMCs.

Synthesis of Pd Nanocrystals Enclosed by {100} Facets and with Sizes 〈10 nm for Application in CO Oxidation

The catalytic activity of noble-metal nanocrystals is mainly determined by their sizes and the facets exposed on the surface. For single crystals, it has been demonstrated that the Pd（100） surface is catalytically more active than both Pd（110） and Pd（111） surfaces for the CO oxidation reaction. Here we report the synthesis of Pd nanocrystals enclosed by {100} facets with controllable sizes in the range of 6-18 nm by manipulating the rate of reduction of the precursor. UV-vis spectroscopy studies indicate that the rate of reduction of Na2PdC14 can be controlled by adjusting the concentrations of Br- and C1- ions added to the reaction mixture. Pd nanocrystals with different sizes were immobilized on ZnO nanowires and evaluated as catalysts for CO oxidation. We found that the activity of this catalytic system for CO oxidation showed a strong dependence on the nanocrystal size. When the size of the Pd nanocrystals was reduced from 18 nm to 6 nm, the maximum conversion rate was significantly enhanced by a factor of -10 and the corresponding maximum conversion temperature was lowered by -80℃.

Fully-exposed Pt clusters stabilized on Sn-decorated nanodiamond/graphene hybrid support for efficient ethylbenzene direct dehydrogenation

The pursuit of energy conservation and environmental protection has always been a hot topic in the catalytic fields,which is inseparable from the rational designing of efficient catalysts and an in-depth understanding of the catalytic reaction mechanism.In this work,fully-exposed Pt clusters were fabricated on the atomically dispersed Sn decorated nanodiamond/graphene(Sn-ND@G)hybrid support and employed for direct dehydrogenation(DDH)of ethylbenzene(EB)to styrene(ST).The detailed structural characterizations revealed the fully-exposed Pt clusters were stabilized on Sn-ND@G,assisted by the spatial separation of atomically dispersed Sn species.The as-prepared Pt/Sn-ND@G catalyst showed enhanced ST yield(136.2 molEB·molpt-1·h-1 EB conversion rate and 99.7%ST selectivity)and robust long-term stability at 500℃for the EB DDH reaction,compared with the traditional ND@G supported Pt nanoparticle catalyst(Pt/ND@G).The ST prefers to desorb from the fully-exposed Pt clusters,resulting in the enhanced DDH catalytic performance of the Pt/Sn-ND@G catalyst.The present work paves a new way for designing highly dispersed and stable supported metal catalysts for DDH reactions.

Fabrication of three dimensional SiC@C hybrid for efficient direct dehydrogenation of ethylbenzene to styrene

Synthesis of hybrid carbon materials with core-shell structure and robust catalytic performance is of great research interest,and remains a great challenge in catalytic dehydrogenation of hydrocarbons reaction.In this paper,few-layer sp^(2) carbon decorated SiC nanocrystals with core-shell structure(SiC@C)were fabricated through a dual-confined magnesiothermic method by employing glucose and SiO_(2) as precursors.The SiC@C nanocrystals were further crosslinked to be a three dimensional(3D)mesoporous hybrid by the in situ generated carbon as binders and exhibiting a 410.30 m^(2) g^(−1) large surface area.The as-prepared SiC@C hybrid materials as metal-free catalysts were evaluated in the steam-free direct dehydrogenation of ethylbenzene to styrene.Benefiting from the abundant surface carbonyl groups on the graphite carbon layers,the optimized yield rate of styrene normalized by carbon mass was as high as 11.58 mmol g^(−1) carbon h^(−1),nearly 4 times that of nanodiamonds.Considering the low cost and excellent catalytic activity,the hybrid 3D SiC@C material may be a promising candidate for direct dehydrogenation of hydrocarbons.

Syntheses and catalytic applications of the high-N-content,the cup-stacking and the macroscopic nitrogen doped carbon nanotubes

The high-N-content, the cup-stacking and the macroscopic nitrogen doped carbon nanotubes（NCNT）were synthesized via an easily manufactured catalytic chemical vapor deposition（CCVD） method. Nitrogen physisorption, transmission electron microscopy（TEM）, thermogravimetric analysis（TGA）, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS） were used to characterize the as-obtained NCNTs. High reaction temperatures were found to be the key point to the formation of inner-cup-stacking NCNTs. However, the synthesis of the outer-cup-stacking NCNT needs special demands not only to the reaction temperature but also to the catalyst and the carrier gas. The possibility of CO oxidation by NCNT was proved to be very small, and the outer-cup-stacking NCNT showed obvious advantage in the oxidative dehydrogenation（ODH） of butene to butadiene compared to a bamboo-like NCNT with an even higher N content.