Structural and chemical transformations of CuZn alloy nanoparticles under reactive redox atmospheres:An in situ TEM study

Alloying metals to form intermetallics has been proven effective in tuning the chemical properties of metal-based catalysts.However,intermetallic alloys can undergo structural and chemical transformations under reactive conditions,leading to changes in their catalytic function.Elucidating and understanding these transformations are crucial for establishing relevant structureperformance relationships and for the rational design of alloy-based catalysts.In this work,we used CuZn alloy nanoparticles(NPs)as a model material system and employed in situ transmission electron microscopy(TEM)to investigate the structural and chemical changes of CuZn NPs under H_(2),O_(2)and their mixture.Our results show how CuZn NPs undergo sequential transformations in the gas mixture at elevated temperatures,starting with gradual leaching and segregation of Zn,followed by oxidation at the NP surface.The remaining copper at the core of particles can then engage in dynamic behavior,eventually freeing itself from the zinc oxide shell.The structural dynamics arises from an oscillatory phase transition between Cu and Cu_(2)O and is correlated with the catalytic water formation,as confirmed by in situ mass spectrometry(MS).Under pure H_(2)or O_(2)atmosphere,we observe different structural evolution pathways and final chemical states of CuZn NPs compared to those in the gas mixture.These results clearly demonstrate that the chemical state of alloy NPs can vary considerably under reactive redox atmospheres,particularly for those containing elements with distinct redox properties,necessitating the use of in situ or detailed ex situ characterizations to gain relevant insights into the states of intermetallic alloy-based catalysts and structure-activity relationships.

Confluence of asymmetric catalysis and electrosynthesis in sustainable chemical transformations

Electrosynthesis has gained widespread recognition for its extraordinary ability to precisely control the redox process.This outstanding capability enables the direct conversion of non-functionalized substrates into reactive intermediates by utilizing easily accessible starting materials, eliminating the need for preliminary functionalization procedures and allowing for unconventional bond activations.

Basic ionic liquids promoted chemical transformation of CO_2 to organic carbonates

Ionic liquids(ILs), especially basic ILs with unique physicochemical properties, have wide application in catalysis. Using basic ILs as catalysts for the conversion of cheap, abundant, nontoxic, and renewable CO_2 into value-added organic carbonates is highly significant in view of environmental and economic issues. This review aims at giving a detailed overview on the recent advances on basic ILs promoted chemical transformation of CO_2 to cyclic and linear carbonates. The structures of various basic ILs, as well as the basic ILs promoted reactions for the transformation of CO_2 to organic carbonates are discussed in detail,including the reaction conditions, the yields of target products, the catalytic activities of basic ILs and the reaction mechanism.

Understanding the stability and reactivity of ultrathin tellurium nanowires in solution： An emerging platform for chemical transformation and material design

The stability and reactivity of nanomaterials are of crucial importance for their application, but the long-term effects of stability and reactivity of nanomaterials under practical conditions are still not well understood. In this study, we first established a comprehensive strategy to investigate the stability of a highly reactive nanomaterial from the viewpoint of reaction kinetics with ultrathin tellurium nanowires （TeNWs） as a model material in aqueous solution through an accelerated oxidation process. This allowed us to propose a new approach for the design and synthesis of other unique one-dimensional nanostructures by a chemical transformation process using the intermediate nanostructures ＂captured＂ during the dynamic oxidation process under different conditions. In essence, the oxidation of ultrathin TeNWs is a gas-solid reaction which involves liquid, gas and solid phases. It has been demonstrated that the oxidation process of ultrathin TeNWs in aqueous solution can be divided into three stages, namely oxygen limiting, ultrathin TeNWs limiting and mass transfer resistance limiting stages. The apparent oxidation kinetics for ultrathin TeNWs is approximately in accord with a first order reaction kinetics model and has an apparent activation energy as low as TeNWs are thermodynamically unstable 13.53 kJ.mol^-1, indicating that ultrathin However, the unstable nature of ultrathin TeNWs is actually an advantage since it can act as an excellent platform to help us synthesize and design one-dimensional functional nanomaterials--with special structures and distinctive properties--which are difficult to obtain by a direct synthesis method.

Functionalized COFs with Quaternary Phosphonium Salt for Versatilely Catalyzing Chemical Transformations of CO_(2)

Currently,it encounters great challenges to accomplish catalyzing various kinds of carbon dioxide(CO_(2))conversion reactions efficiently with single catalyst,let alone control the interplay among catalytic efficiency and selectivity evenly.Here,we prepared a functional covalent organic framework,[PTPP]X%-TD-COF[PTPP=3-bromopropyltriphenylphosphonium;TD=1,3,5-tri(4-aminophenyl)benzene-1,4-diformylbenzene],by immobilizing the quaternary phosphonium salt onto the skeleton of COFs through a post-synthesis strategy for versatilely catalyzing reduction of CO_(2) and CO_(2) fixation on epoxide and aziridine facilely.With the typical features of COFs(such as porosity and ordered structure)and catalytic activity of the quaternary phosphonium salt,[PTPP]X%-TD-COF possesses an intensely synergistic effect for catalyzing the chemical transformations of CO_(2).Noteworthily,the quaternary phosphonium salt functionalized COFs catalyze the CO_(2) reduction reaction with amine and phenylsilane to produce formylated and methylated products under gentle reaction conditions with high selectivity and efficiency.Furthermore,[PTPP]_(X%)-TD-COF shows high catalytic ability in CO_(2) chemical fixation reactions.

Facet-dependent transformation and toxicity of nanoscale zinc oxide in the synthetic saliva

The nanoscale zinc oxide(n-ZnO)was used in food packages due to its superior antibac terial activity,resulting in potential intake of n-ZnO through the digestive system,wherein n-ZnO interacted with saliva.In recent,facet engineering,a technique for controlling the exposed facets,was applied to n-ZnO,whereas risk of n-ZnO with specific exposed facets in saliva was ignored.ZnO nanoflakes(ZnO-0001)and nanoneedles(ZnO-1010)with the pri mary exposed facets of{0001}and{1010}respectively were prepared in this study,investigat ing stability and toxicity of ZnO-0001 and ZnO-1010 in synthetic saliva.Both ZnO-0001 and ZnO-1010 partially transformed into amorphous Zn_(3)(PO_(4))_(2)within 1 hr in the saliva even containing orgnaic components,forming a ZnO-Zn_(3)(PO_(4))_(2)core-shell structure.Neverthe less,ZnO-1010 relative to ZnO-0001 would likely transform into Zn_(3)(PO_(4))_(2),being attributed to superior dissolution of{1010}facet due to its lower vacancy formation energy(1.15 eV than{0001}facet(3.90 eV)).The toxicity of n-ZnO to Caco-2 cells was also dependent on the primary exposed facet;ZnO-0001 caused cell toxicity through oxidative stress,whereas ZnO-1010 resulted in lower cells viability than ZnO-0001 through oxidative stress and mem brane damage.Density functional theory calculations illustrated that·O_(2)^(-)was formed and released on{1010}facet,yet O_(2)^(2-)instead of·O_(2)^(-)was generated on{0001}facet,leading to low oxidative stress from ZnO-0001.All findings demonstrated that stability and toxicity of n-ZnO were dependent on the primary exposed facet,improving our understanding o health risk of nanomaterials.

Optimization of Contents of Three Raw Clay Materials in Formulation of a Porcelain

Formulation of traditional hard porcelain generally requires 50% kaolin, 25% silica and 25% feldspar. Four porcelains formulation using the casting method, were prepared with different percentages of kaolinitic clay, sand and pegmatite referenced respectively NONG, SAB and PEG. The physico-chemical, mechanical and mineralogical characteristics were evaluated on specimens formulated and sintered at different temperatures from 1200˚C to 1300˚C. X-ray diffraction has revealed the presence of mullite and quartz as essentially crystalline phases. The specimen formulated with 55% NONG, 25% PEG and 20% SAB and sintered at 1240˚C gives better performance (water absorption: 0.17%, density: 2.42, open porosity: 0.42% and flexural strength: 53.54 MPa).

Strong and tough chitin hydrogel constructed by dehydration and rehydration strategy

As a renewable,biocompatible,biodegradable soft material,chitin hydrogels have better advantages in stability,antibacterial activity,antifouling,cost,immunogenicity,and so on than most polymer hydrogels.However,compared with other widely used polymer hydrogels with high strength and toughness,the practical applications of chitin-based hydrogels have been limited by their weak mechanical properties,such as cartilage repair and meniscus replacement.Here,we present the design and fabrication of chitin hydrogels with excellent mechanical strength and toughness by a dehydration and rehydration strategy.By sequential dehydration and rehydration processes,the crystalline domains in the chitin hydrogels can be properly controlled.With optimized crystallinity,the elastic modulus of the chitin hydrogels exceeds all previously reported values,and the fracture toughness is even comparable to some synthetic polymer hydrogels,while maintaining a high-water-content of about 80 wt.%.At the same water content,the mechanical properties of the chitin hydrogels are positively correlated with the hydrogel crystallinity,which proves that the change of mechanical properties of hydrogels is not simply dependent on weight concentration.The hydrogels can be further strengthened by incorporating other biopolymers that are intrinsically weak,which makes the hydrogels promising for applications in fields such as cartilage repair and meniscus replacement.Moreover,the hydrogels enable loading and release of water-soluble and poorly water-soluble drugs.This highly extendable strengthening and toughening strategy of chitin and chitin-based biopolymer hydrogels paves the way for their widely applications.

In situ electrochemically converting Fe_2O_3-Ni(OH)_2 to NiFe_2O_4-NiOOH:a highly efficient electrocatalyst towards water oxidation

To develop low-cost, earth-abundant NiFe- based materials as highly efficient oxygen evolution reaction （OER） electrocatalysts and to probe new catalytic species are still great challenges to now. Here, an in situ forma- tion of OER active NiFe2O4-NiOOH nanosheet arrays is demonstrated as a highly efficient OER electrocatalyst by the anodization of Fe203 domains anchored on Ni（OH）2 nanosheet arrays. The as-converted product can deliver the current density of 30 mA cm-2 with a small overpotential of 240 mV, and only requires an overpotential of 410 mV to achieve an amazing huge current density of 3000 mA cm-2. In situ potential-dependent Raman spectroscopy reveals that Ni（OH）2 in the composite is easier to be oxidized to NiOOH than pure Ni（OH）2, and the newly formed NiOOH reacts with the nearby Fe2O3 to produce hybrid NiFe2O4-NiOOH. It is found that the cooperative effect of the in situ formed NiFe2O4 and NiOOH as well as the hydrophilic and aero- phobic electrode surface make main contribution to the outstanding OER activity of the catalyst. This work will bring new perspectives to the recognition of the origin of NiFe composite materials for OER and provide a mild method to synthesize amorphous spinel materials at room temperature.

Theory, Technology and Practice of Unconventional Petroleum Geology

0 INTRODUCTION The breakthroughs in unconventional petroleum have a great impact on world petroleum industry and innovation in petroleum geology(Dou et al,2022;Jia,2017;Zou et al.,2015b,2014a;Yerkin,2012;Pollastro,2007;Schmoker,1995).The exploration and development evolution from conventional petroleum to unconventional petroleum and more and more frequent industrial activities of exploring petroleum inside sources kitchen have deepened theoretical understanding of unconventional petroleum geology and promoted technical research and development(Jia et al.,2021,2017;Jin et al.,2021;Zhao W Z et al.,2020;Ma Y S et al.,2018,2012;Zou et al.,2018b,2016,2009;Dai et al.,2012).We have introduced and extended the theory of continuous hydrocarbon accumulation since 2008 and published several papers/books(in Chinese and English)with respect to unconventional petroleum geology since 2009,basically forming the theoretical framework for this discipline(Yang et al.,2022a,2021a,2019a,,2015a;Zou et al.,2019c,2017b,2014a,,2013a).In this paper,we present the background of unconventional petroleum geology,review the latest theoretical and technological progress in unconventional petroleum geology,introduce relevant thinking and practices in China,and explore the pathway of unconventional petroleum revolution and multi-energy coordinated development in super energy basins,hopefully to promote the unconventional petroleum geology and industry development.

Organophosphorus catalytic reaction based on reduction of phosphine oxide

The special electronic configuration of phosphorus atoms endows organophosphorus reagents with unique chemical properties,which enable them to be used to catalyze various organic reactions,such as the Wittig reaction,Staudinger reaction,Appel reaction and Mitsunobu reaction.However,the catalytic process will be accompanied by the generation of large amounts of phosphine oxide waste,resulting in the reduction of atom utilization of the reaction,and it is difficult to separate the product.Therefore,it is essential to explore a greener and more sustainable organic synthesis route based on the catalytic cycle of phosphine oxide as a model.This paper summarizes the catalytic cycle and recycling of phosphorus with or without reducing agents and reviews the related developments in recent decades:from the addition of stoichiometric strong reducing agents,to the design of ring phosphines with specific structures,to the development of new energy inputs(electrochemistry),to the addition of a series of compounds to activate the P(V)––O double bond,driving the catalytic cycle of phosphine oxide through chemical transformation.This review also points out the development potential of this field in the future,which will promote its development and progress in a greener direction.

Ultrathin Ti_(3)C_(2) nanowires derived from multi-layered bulks for high-performance hydrogen evolution reaction

One-dimensional ultrathin nanowires(NWs)offer a great deal of promising properties for electrochemical energy storage and conversion due to their nanoscale confinement effect and high surface-to-volume ratios.It is highly desirable to precisely design and synthesize ultrathin Ti_(3)C_(2)NWs in the aspect of size,crystalline structure and composition.Here,we report a simple alkalization strategy to design the ultrathin Ti_(3)C_(2)NWs for hydrogen evolution reaction(HER)by modulating the surface-active sites.The design principle can well improve the amount of the defect sites and ion accessibility to increase the interactions between Ti_(3)C_(2)NWs and H^(*).The optimized Ti_(3)C_(2)NWs achieve an overpotential of 476 mV at the current density of 10 mA/cm^(2)and a Tafel slope of 129 mV/dec for HER catalysis,which are superior to that of Ti_(3)C_(2)nanosheets and m-Ti_(3)C_(2).It paves an avenue for the rational transformation of MXene bulks to one-dimensional NWs catalysts for HER.

Preparation and reaction of bis (perfluoroalkanesulfonyl) methyl halides

Halogenation of the potassium or silver salts of bis(trifluoromethanesulfonyl)methane (CF3SO2)2CH2 and its cyclo analogues 1 with N-fluoro-bis(trifluoromethanesulfonyl)imine [(CF3SO3)2NF], chlorine or bromine gave good yields of the corresponding α-halo disulfone (CF3SO2)2CHX and cyclo analogues 9, 10. The chemical transformation of these fluorinated α-halo-disulfones are described.