间隙碳调控Ni实现1,3-丁二烯高效加氢

选择性加氢反应是化工生产中一类重要的催化反应。其中,1,3-丁二烯选择性加氢对提纯单烯烃、防止聚合反应催化剂中毒等具有重要作用。利用负载型钯基催化剂进行选择性加氢脱除炔烃是现阶段工业生产中广泛采用的方法,但仍存在价格昂贵、丰度低等问题。因此,研制具有优良催化性能的非贵金属催化剂一直是工业研究的重点。在此,本工作利用浸渍法制备了Ni_(3)Zn/Al_(2)O_(3)催化剂,并进一步以气体驱动法获得Ni_(3)ZnC_(0.7)/Al_(2)O_(3)催化剂,通过X射线衍射、透射电子显微镜、X射线光电子谱等表征分析了间隙碳对Ni_(3)Zn/Al_(2)O_(3)催化剂结构的影响,并关联两种催化剂在1,3-丁二烯选择性加氢反应中的催化性能,建立构效关系。催化性能测试结果表明Ni_(3)ZnC_(0.7)/Al_(2)O_(3)催化剂具有优异的单烯烃选择性,在1,3-丁二烯转化率为98%时,丁烯选择性高达93%,明显优于Ni_(3)Zn/Al_(2)O_(3)催化剂。CO-原位漫反射红外傅里叶变换光谱表征揭示引入间隙碳原子后Ni变的缺电子,更利于单烯烃脱附,抑制了单烯烃进一步加氢路径而促进性能提升。这项工作为非贵金属加氢催化剂的设计和研制提供新思路。

Finned Zn-MFI zeolite encapsulated noble metal nanoparticle catalysts for the oxidative dehydrogenation of propane with carbon dioxide

Oxidative dehydrogenation of propane with carbon dioxide(CO_(2)-ODP)characterizes the tandem dehydrogenation of propane to propylene with the reduction of the greenhouse gas of CO_(2)to valuable CO.However,the existing catalyst is limited due to the poor activity and stability,which hinders its industrialization.Herein,we design the finned Zn-MFI zeolite encapsulated noble metal nanoparticles(NPs)as bifunctional catalysts(NPs@Zn-MFI)for CO_(2)-ODP.Characterization results reveal that the Zn2+species are coordinated with the MFI zeolite matrix as isolated cations and the NPs of Pt,Rh,or Rh Pt are highly dispersed in the zeolite crystals.The isolated Zn2+cations are very effective for activating the propane and the small NPs are favorable for activating the CO_(2),which synergistically promote the selective transformation of propane and CO_(2)to propylene and CO.As a result,the optimal 0.25%Rh0.50%Pt@Zn-MFI catalyst shows the best propylene yield,satisfactory CO_(2)conversion,and long-term stability.Moreover,considering the tunable synergetic effects between the isolated cations and NPs,the developed approach offers a general guideline to design more efficient CO_(2)-ODP catalysts,which is validated by the improved performance of the bifunctional catalysts via simply substituting Sn4+cations for Zn2+cations in the MFI zeolite matrix.

Cooperative catalytic platinum species accelerating polysulfide redox reactions for Li-S batteries

The shuttle effect derived from diffusion of lithium polysulfides(LiPSs) and sluggish redox kinetic bring about poor cycling stability and low utilization of sulfur,which have always been the key challenging issues for the commercial application of lithium-sulfur(Li-S) batteries.Rational design of cathode materials to catalyze Li_(2)S dissociation/nucleation processes is an appealing and valid strategy to develop high-energy practical Li-S batteries.Herein,considering the synergistic effect of bidirectional catalysis on LiPSs conversion and enhanced chemical immobilization for LiPSs by heteroatom doping,Pt nanoparticles loaded on nitrogen-doped carbon spheres(Pt/NCS composites) were constructed as cathode materials.According to the dynamic evolution of Pt catalysts and sulfur species,Pt~0 and Pt^(2+) species were identified as active species for the accelerated dissociation and nucleation of Li_(2)S,respectively.Meanwhile,in-situ Raman results demonstrated the expedited conversion of sulfur species resulted from bidirectional catalysis of active Pt species,corresponding to boosted redox kinetics.Consequently,Pt/NCS cathode exhibited improved long-term cyclability with high initial capacity,along with enhanced rate capability.This work provides a facile approach to construct cathode materials with bidirectional catalysis on Li_(2)S dissociation/nucleation,and sheds light on a more global understanding of the catalytic mechanism of metal catalysts during LiPSs conversion.

A scaffold vaccine to promote tumor antigen cross-presentation via sustained toll-like receptor-2(TLR2)activation

Cancer vaccination holds great promise for cancer treatment,but its effectiveness is hindered by suboptimal activation of CD8+cytotoxic T lymphocytes,which are potent effectors to mediate anti-tumor immune responses.A possible solution is to switch antigen-presenting cells to present tumor antigens via the major histocompatibility complex class I(MHC-I)to CD8+T cells-a process known as cross-presentation.To achieve this goal,we develop a three-dimensional(3D)scaffold vaccine to promote antigen cross-presentation by persisted toll-like receptor-2(TLR2)activation after one injection.This vaccine comprises polysaccharide frameworks that“hook”TLR2 agonist(acGM)via tunable hydrophobic interactions and forms a 3D macroporous scaffold via click chemistry upon subcutaneous injection.Its retention-and-release of acGM enables sustained TLR2 activation in abundantly recruited dendritic cells in situ,inducing intracellular production of reactive oxygen species(ROS)in optimal kinetics that crucially promotes efficient antigen cross-presentation.The scaffold loaded with model antigen ovalbumin(OVA)or tumor specific antigen can generate potent immune responses against lung metastasis in B16-OVA-innoculated wild-type mice or spontaneous colorectal cancer in transgenic ApcMin/+mice,respectively.Notably,it requires neither additional adjuvants nor external stimulation to function and can be adjusted to accommodate different antigens.The developed scaffold vaccine may represent a new,competent tool for next-generation personalized cancer vaccination.

Chemical Electron Microscopy(CEM)for Heterogeneous Catalysis at Nano:Recent Progress and Challenges

Chemical electron microscopy(CEM),a toolbox that comprises imaging and spectroscopy techniques,provides dynamic morphological,structural,chemical,and electronic information about an object in chemical environment under conditions of observable performance.CEM has experienced a revolutionary improvement in the past years and is becoming an effective characterization method for revealing the mechanism of chemical reactions,such as catalysis.Here,we mainly address the concept of CEM for heterogeneous catalysis in the gas phase and what CEM could uniquely contribute to catalysis,and illustrate what we can know better with CEM and the challenges and future development of CEM.

Modulating macrophage activities to promote endogenous bone regeneration: Biological mechanisms and engineering approaches

A coordinated interaction between osteogenesis and osteoimmune microenvironment is essential for successful bone healing.In particular,macrophages play a central regulatory role in all stages of bone repair.Depending on the signals they sense,these highly plastic cells can mediate the host immune response against the exterior signals of molecular stimuli and implanted scaffolds,to exert regenerative potency to a varying extent.In this article,we first encapsulate the immunomodulatory functions of macrophages during bone regeneration into three aspects,as sweeper,mediator and instructor.We introduce the phagocytic role of macrophages in different bone healing periods(‘sweeper’)and overview a variety of paracrine cytokines released by macrophages either mediating cell mobilisation,vascularisation and matrix remodelling(‘mediator’),or directly driving the osteogenic differentiation of bone progenitors and bone repair(‘instructor’).Then,we systematically classify and discuss the emerging engineering strategies to recruit,activate and modulate the phenotype transition of macrophages,to exploit the power of endogenous macrophages to enhance the performance of engineered bone tissue.

Statistical morphological identification of low-dimensional nanomaterials by using TEM

Nanomaterials with low-dimensional morphology display unique properties in catalysis and related fields,which are highly dependent on the structure and aspect ratio.Thus,accurate identification of the structure and morphology is the basis to correlate to the performance.However,the widely adopted techniques such as XRD is incapable to precise identify the aspect ratio of low-dimensional nanomaterials,not even to quantify the morphological uniformity with statistical deviation value.Herein,ZnO nanorod and nanosheet featured with one-and two-dimensional morphology were selected as model materials,which were prepared by the hydrothermal method and statistically characterized by transmission electron microscopy(TEM).The results indicate that ZnO nanorods and nanosheets display rod-like and orthohexagnal morphology,which mainly encapsulated with{100}and{001}planes,respectively.The 7.36±0.20 and 0.39±0.02 aspect ratio(c/a)of ZnO nanorods and nanosheets could be obtained through the integration of the(100)and(002)diffraction rings in selected area electron diffraction(SAED).TEM combining with the SAED is favorable compare with XRD,which not only provides more accurate aspect ratio results with standard deviation values but also requires very small amounts of sample.This work is supposed to provide a convenient and accurate method for the characterization of nanomaterials with low-dimensional morphology through TEM.

Facile-fabricated iron oxide nanorods as a catalyst for hydrogenation of nitrobenzene

b-FeOOH nanorods were prepared by a poly ethylene glycol(PEG) assisted precipitation of FeCl_3·6 H_2O aqueous solution with urea. Na_2CO_3 aqueous solution was introduced to maintain their shapes under annealing. The one-dimensional porous iron oxide nanorods were synthesized successfully. The asprepared catalysts were characterized by X-ray diffraction, transmission electron microscopy, N_2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy. The hydrogenation of nitrobenzene to aniline was taken as probe reaction to evaluate their catalytic performance. FeOOH(iron oxides hydroxide) nanorods, fabricated by annealing b-FeOOH nanorods at 250℃ in Ar atmosphere for 4h, exhibited high catalytic activity for the transfer hydrogenation of nitrobenzene to aniline with hydrazine hydrate as hydrogen donors.

Identify fine microstructure of multifarious iron oxides via O K-edge EELS spectra

Relying on the electron energy loss spectrum(EELS)of metallic elements to obtain microstructure analysis is an investigation method of the reaction mechanisms of transition metal oxides(TMOs)in catalysis,energy storage and conversion.However,the low signal from K shell owing to insufficient electron beam energy,and the complicated electronic structure in L shell of the metal element restrict the analysis of the coordination environment of the TMOs.Herein,density functional theory(DFT)calculation,Fourier transform(FT)and wavelet transform(WT)were employed to probe the relationship between the four individual peaks in O K-edge spectra of iron oxides and the microstructure information(chemical bonds and atomic coordination).The findings show that the peak amplitude ration is in a linear correlation with the valence state of Fe element,and that the coordination number obtained by radial distribution function(RDF)is favorably linearly correlative with that from the standard coordination structure model.As a result,the quantitative analysis on the change of valence state and atomic coordination in microstructure can be realized by EELS O K-edge spectra.This study establishes EELS O K-edge spectrum as a promising pathway to quantitatively analyze the valence state and atomic coordination information of TMOs,and offers an effective method to conduct microstructure analysis via the EELS spectra of the non-metal element.

Tailoring the surface structure of iron compounds to optimize the selectivity of 3-nitrostyrene hydrogenation reaction over Pt catalyst

Selective hydrogenation of substituted nitroarenes is an important reaction to obtain amines.Supported metal catalysts are wildly used in this reaction because the surface structure of supports can tune the properties of the supported metal nanoparticles(NPs)and promote the selectivity to amines.Herein,Pt NPs were immobilized on Fe OOH,Fe_(3)O_(4)andα-Fe_2O_(3)nanorods to synthesize a series of iron compounds supported Pt catalysts by liquid phase reduction method.Chemoselective hydrogenation of 3-nitrostyrene to 3-aminostyrene was used as probe reaction to evaluate the performance of the catalysts.The results show that Pt/Fe OOH exhibits the highest selectivity and activity.Fe OOH support with pores and-OH groups can tune the electronic structure of Pt NPs.The positive charge of Pt NPs supported on Fe OOH is key factor for improving the catalytic performance.