金属有机骨架材料(MOFs)用于乙烷/乙烯的高效分离

乙烯是重要的石油化工原料之一,在其生产过程中会产生乙烷等杂质气体,乙烷与乙烯的物理性质接近,采用传统精馏分离能耗较高。变压吸附工艺绿色高效,但是缺乏高效的乙烷选择性吸附剂。金属有机骨架材料(MOFs)是一类由金属离子与有机配体搭建而成的多孔配位聚合物,因其具有高比表面积、高孔隙率等优势,近年来在低碳烃分离领域显示出巨大的应用潜力。笔者介绍了系列乙烷选择性MOFs材料,其独特的结构能够比较好地选择性吸附乙烷,从而实现高效纯化乙烯气体,直接分离得到纯度≥99.95%的聚合级乙烯产品。综合前期的研究成果,指出提高乙烷选择性MOFs材料的选择性、吸附量及稳定性是未来该材料发展的重要方向。

Boosting CO_(2) photoreduction by synergistic optimization of multiple processes through metal vacancy engineering

The photoreduction of greenhouse gas CO_(2) using photocatalytic technologies not only benefits en-vironmental remediation but also facilitates the production of raw materials for chemicals.Howev-er,the efficiency of CO_(2) photoreduction remains generally low due to the challenging activation of CO_(2) and the limited light absorption and separation of charge.Defect engineering of catalysts rep-resents a pivotal strategy to enhance the photocatalytic activity for CO_(2),with most research on met-al oxide catalysts focusing on the creation of anionic vacancies.The exploration of metal vacancies and their effects,however,is still underexplored.In this study,we prepared an In2O3 catalyst with indium vacancies(VIn)through defect engineering for CO_(2) photoreduction.Experimental and theo-retical calculations results demonstrate that VIn not only facilitate light absorption and charge sepa-ration in the catalyst but also enhance CO_(2) adsorption and reduce the energy barrier for the for-mation of the key intermediate*COOH during CO_(2) reduction.Through metal vacancy engineering,the activity of the catalyst was 7.4 times,reaching an outstanding rate of 841.32μmol g(-1)h^(-1).This work unveils the mechanism of metal vacancies in CO_(2) photoreduction and provides theoretical guidance for the development of novel CO_(2) photoreduction catalysts.

采用CdTe压盖层的本征p型HgCdTe

本发明提供一种确定HgCdTe衬底中金属空位浓度的方法。该方法的实施步骤为:在HgCdTe衬底上压盖一层富碲的CdTe,然后在足以支持富碲CdTe层与HgCdTe衬底之间互相扩散的温度下对该衬底进行退火。此外。

CO oxidation over Au/ZrLa-doped CeO_2 catalysts: Synergistic effect of zirconium and lanthanum

The physicochemical properties of nanosized Au catalysts supported on doped CeO2 and their cata‐lytic performance for the CO oxidation reaction were investigated. The Au/Zr‐doped CeO2 catalyst is much more active than undoped Au/CeO2, while Au/ZrLa‐doped CeO2 shows the highest activity. Characterization of the catalysts by X‐ray diffraction, transmission electron microscopy （TEM）, high‐resolution TEM, and the X‐ray absorption fine structure technique shows high homogeneity of the oxide supports and well‐dispersed nanosized Au nanoparticles. Raman spectroscopy, X‐ray photoelectron spectroscopy, and H2‐tempeature‐programmed reduction show that the surface oxygen species are the main factor for the catalytic activity in the CO oxidation reaction, while the supported Au species can improve the redox properties and create oxygen vacancy sites on the support. The oxidation state of Au is not the main factor governing the activity of Au/doped‐CeO2 catalysts. Additionally, the synergistic effect of Zr and La is discussed.

Photo-enhanced thermal catalytic CO_(2) methanation activity and stability over oxygen-deficient Ru/TiO_(2) with exposed TiO_(2){001}facets:Adjusting photogenerated electron behaviors by metal-support interactions

In this study,two Ru/TiO_(2)samples with different TiO_(2)facets were prepared to investigate their photo-thermal catalytic CO_(2)+H_(2)reaction behavior.Without UV irradiation,the Ru/TiO_(2)with 67%{001}facet(3 RT)displayed improved thermal catalytic activity for CO_(2)methanation than that of Ru/TiO_(2)with 30%{001}facet(0 RT).After H_(2)pretreatment,both samples exhibited enhanced thermal catalytic activities,but the H_(2)-treated 3 RT(3 RT-H)exhibited superior activity to that of the H_(2)-treated 0 RT(0 RT-H).Under UV irradiation,3 RT-H exhibited apparent photo-promoted thermal catalytic activity and stability,but the enhanced catalytic activity was lower than that of 0 RT-H.Based on the characterization results,it is proposed that both the surface oxygen vacancies(Vos)(activating CO_(2))and the metallic Ru nanoparticles(activating H_(2))were mainly responsible for CO_(2)methanation.For 0 RT,H_(2)pretreatment and subsequent UV irradiation did not promote the formation of Vos,resulting in low catalytic activity.For 3 RT,on the one hand,H_(2)pretreatment promoted the formation of Vos,which were regenerated under UV irradiation;on the other hand,the photogenerated electrons from TiO_(2)transferred to Ru to maintain the metallic Ru nanoparticles.Both behaviors promoted the activation of CO_(2)and H_(2)and enhanced CO_(2)methanation.Moreover,the photogenerated holes favored the dissociated H at Ru migrating to TiO_(2),also promoting CO_(2)methanation.These behaviors occurring on 3 RT-H may be attributed to the suitable metal-support interaction between the Ru nanoparticles and TiO_(2){001},resulting in the easy activation of lattice oxygen in TiO_(2)to Vos.With reference to the analysis of intermediates,a photo-thermal reaction mechanism is proposed for the Ru/TiO_(2){001}facet sample.

UV Laser Regulation of Surface Oxygen Vacancy of CoFe2O4 for Enhanced Oxygen Evolution Reaction

Oxygen evolution reaction is one of the key processes in the promising renewable energy technique of electrocatalytic water splitting.Developing high ecient oxygen evolution reaction(OER)catalysts requires determination of the optimal values of the descriptor parameters.Using spinel CoFe2O4 as the model catalyst,this work demonstrates that irradiation with pulsed UV laser can control the quantity of surface oxygen vacancy and thus modify the OER activity,in a volcano-shape evolution trend.This strategy sheds light on quantita-tively investigation of the relationship between surface cation valence,anion vacancy,and physicochemical properties of transition-metal-based compounds.

Well Dispersed SnO2 Nanoclusters Preparation and Modulation of Metal-Insulator Transition Induced by Ionic Liquid

Tin dioxide (SnO2) has attracted broad interest due to its particular gas-sensor property. Nano- or atom-scale SnO2 material has always been the aim in order to ultimately improve the sensitivity. However, until now, it remains difficult to synthesize SnO2 nanoclusters by using traditional methods. In the present work, we have achieved the preparation of SnO2 nanoclusters by using the cluster beam deposition technique. The obtained nanoclusters were well characterized by high resolution transmission electron microscope HR-TEM. Results indicated the formation of the well-dispersed SnO2 nanoclusters with uniform size distribution (5-7 nm). Furthermore, an obvious metal insulator transition was observed by gating with ionic liquid. Combined with theory calculation, the corresponding mechanism was systematically analyzed from oxygen vacancy induced electron doping.

^(15)N/^(14)N Isotopic Exchange in the Dissociative Adsorption of N_(2) on Tantalum Nitride Cluster Anions Ta_(3)N_(3)

Adsorption and activation of dinitrogen(N_(2)) is an indispensable process in nitrogen fixation.Metal nitride species continue to attract attention as a promsing catalyst for ammonia synthesis.However,the detailed mechanisms at a molecular level between reactive nitride species and N_(2) remain unclear at elevated temperature,which is important to understand the temperature effect and narrow the gap between the gas phase system and condensed phase system.Herein,the ^(15)N/^(14)N isotopic exchange in the reaction between tantalum nitride cluster anions Ta_(3)^(14)N_(3)^(-) and ^(15)N_(2) leading to the regeneration of ^(14)N_(2)/^(14)N^(15)N was observed at elevated temperature(393-593 K)using mass spectrometry.With the aid of theoretical calculations,the exchange mechanism and the effect of temperature to promote the dissociation of N_(2) on Ta_(3)N_(3)^(-) were elucidated.A comparison experiment for Ta_(3)^(14)N_(4)^(-)/^(15)N_(2) couple indicated that only desorption of ^(15)N_(2) from Ta_(3)^(14)N_(4)^(15)N_(2)^(-) took place at elevated temperature.The different exchange behavior can be well understood by the fact that nitrogen vacancy is a requisite for the dinitrogen activation over metal nitride species.This study may shed light on understanding the role of nitrogen vacancy in nitride species for ammonia synthesis and provide clues in designing effective catalysts for nitrogen fixation.

Metal-induced oxygen vacancies on Bi_(2)WO_(6)for efficient CO_(2) photoreduction

Semiconductor-based photocatalysis for efficient solar energy conversion is an ideal strategy to tackle the growing global energy and environmental crisis.However,the development of photocatalysis is still limited by problems such as low utilization of visible light,low efficiency of charge transfer and separation,and insufficient reactive sites.Herein,Au nanoparticles(NPs)were deposited on the surface of Bi_(2)WO_(6)by a one-step reduction method,which simultaneously induced the formation of oxygen vacancies(OVs)on the surface of Bi_(2)WO_(6).The OVs concentration is found to be increased with the increase of Au loading.Au NPs and OVs improve the light absorption and facilitate the separation and transport of the photogenerated carriers.In addition,OVs act synergistically with the nearby metal active sites to optimize the adsorption energy of reactants on the catalyst surface,changing the adsorption form of CO_(2)molecules on the catalyst surface.The as-synthesized photocatalyst achieved a photocatalytic performance of up to 34.8μmol g^(−1)h^(−1)of CO_(2)reduction to CO without sacrificial agent in a gas-solid system,which is 9.4 times higher than that of the pristine Bi_(2)WO_(6).This work may further deepen our understanding on the relationship between metal NPs and OVs,and their combined role in photocatalysis.

Oxygen vacancies boosting ultra-stability of mesoporous ZnO-CoO@N-doped carbon microspheres for asymmetric supercapacitors

Long-term cycling stability of pseudocapacitive materials is pursued for high-energy supercapacitors.Herein,the mesoporous zinc-cobalt oxide heterostructure@nitrogendoped carbon(ZnO-CoO@NC)microspheres with abundant oxygen vacancies are self-assembled through a hydrothermal method combined with an annealing post-treatment.The multifunctional polyvinyl pyrrolidone(PVP)is used as a structure-directing agent,the precursor of NC and the initiator of abundant oxygen vacancies in zinc-cobalt oxide microspheres.XPS demonstrates the generation of surface oxygen vacancies resulted from the reduction effect of conductive NC,and further confirms the weaker interaction between the metal ions and oxygen atoms.As a result,the electrode based on ZnO-CoO@NC in 2 mol L^-1 KOH shows enhanced capacitive performance with an excellent cycle stability of 92%retention of the initial capacitance after 40,000 charge-discharge cycles at 2 A g^-1,keeping the morphology unchanged.The assembled asymmetric supercapacitor,graphene//ZnO-CoO@NC,also performs good cyclic stability with 94%capacitance retention after 10,000 cycles at 2 A g^-1.The remarkable electrochemical performance of the self-assembled ZnO-CoO@NC composite is attributed to the mesoporous architecture,abundant oxygen vacancies,conductive ZnO scaffold for CoO crystals forming heterostructure of ZnO-CoO and the high conductive NC layer covering outside of the multi-metal oxide nanoparticles.Hence,the ZnO-CoO@NC holds great promise for high-performance energy storage applications.

Defect engineered 2D mesoporous Mo-Co-O nanosheets with crystalline-amorphous composite structure for efficient oxygen evolution

Two-dimensional(2D)mesoporous metal-oxide(hydroxide)nanomaterials with defects are promising towards the realization of efficient electrocatalysis.Herein,we report a facile and effective one-pot solvothermal route to synthesize mesoporous Mo_(x)-Co-O hybrid nanosheets(NSs)which is composed of crystalline Mo_(4)O_(11) and amorphous cobalt hydroxide.Due to the corrosion of 1-octylamine at high temperatures,abundant mesoporous holes are created in situ over the Mo_(x)-Co-O hybrid NSs during the solvothermal process,which is beneficial to increasing the electrochemical surface area.The dimension of the Mox-Co-O NSs,size of mesoporous and the concentration of defects can be easily modulated by controlling the molar ratio of Mo/Co.Electrochemical measurements reveal that the 2D mesoporous Mo_(x)-Co-O NSs show an excellent activity for the oxygen evolution reaction with the highest catalytic activity of η_(10)=276 mV at 10 mA cm^(−2)in 1 mol L^(−1)KOH.Enhanced adsorption of intermediates and abundant oxygen vacancies achieved by appropriate Mo doping are the two main factors that contribute to the excellent catalytic activity of Mo_(0.2)-Co-O NSs.This work,with the construction of 2D metal-oxide(hydroxide)crystallineamorphous nanomaterials possessing abundant holes,oxygen vacancies and enhanced adsorption of intermediates,provides important insight on the design of more efficient catalysts.

Defects production and mechanical properties of typical metal engineering materials under neutron irradiation

Maintaining the safety and reliability of nuclear engineering materials under a neutron irradiation environment is significant. Atomic-scale simulations are conducted to investigate the mechanism of irradiation-induced vacancy formation in CLAM, F82 H and α-Fe with different neutron energies and objective laws of the effect of vacancy concentration on mechanical properties of α-Fe. Damage of these typical metal engineering materials caused by neutrons is mainly displacement damage, while the displacement damage rate and the non-ionizing effect of neutrons decrease with the increase of neutron energy. The elastic modulus, yield strength, and ultimate strength of α-Fe are in the order of magnitude of GPa. However, the elastic modulus is not constant but decreases with the increase of strain at the elastic deformation stage. The ultimate strength reaches its maximum value when vacancy concentration in α-Fe is 0.2%. On this basis, decreasing or increasing the number of vacancies reduces the ultimate strength.

A highly-efficient oxygen evolution electrode based on defective nickel-iron layered double hydroxide

Exploring efficient and cost-effective electro- catalysts for oxygen evolution reaction （OER） is critical to water splitting. While nickel-iron layered double hydroxide （NiFe LDH） has been long recognized as a promising non- precious electrocatalyst for OER, its intrinsic activity needs further improvement. Herein, we design a highly-efficient oxygen evolution electrode based on defective NiFe LDH na- noarray. By combing the merits of the modulated electronic structure, more exposed active sites, and the conductive elec- trode, the defective NiFe LDH electrocatalysts show a low onset potential of 1.40 V （vs. RHE）. An overpotential of only 200 mV is required for 10 mA cm-2, which is 48 mV lower than that of pristine NiFe-LDH. Density functional theory plus U （DFT＋U） calculations are further employed for the origin of this OER activity enhancement. We find the introduction of oxygen vacancies leads to a lower valance state of Fe and the narrowed bandgap, which means the electrons tend to be ea- sily excited into the conduction band, resulting in the lowered reaction overpotential and enhanced OER performance.

Phosphorus-doped MoS_(2) with sulfur vacancy defects for enhanced electrochemical water splitting

MoS_(2)is a promising electrocatalyst because of its natural abundance and outstanding electrochemical stability.However,the poor conductivity and low activity limit its catalytic performance;furthermore,MoS_(2)is unable to satisfy the requirements of most industrial applications.In this study,to obtain a P-doped MoS_(2)catalyst with S vacancy defects,P is inserted into the MoS_(2)matrix via a solid phase ion exchange at room temperature.The optimal P-doping amount is 11.4 wt%,and the resultant catalyst delivers excellent electrocatalytic properties for the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)with the corresponding overpotentials of 93 and 316 mV at 10 mA cm^(-2) in an alkaline solution;these values surpass the overpotentials of most previously reported MoS_(2)-based materials.Theoretical calculations and results demonstrate that the synergistic effect of the doped P,which forms active centers in the basal plane of MoS_(2),and S vacancy defects caused by P doping intensifies the intrinsic electronic conductivity and electrocatalytic activity of the catalyst.Density functional theory calculations demonstrate that P optimizes the free energy of the MoS_(2)matrix for hydrogen adsorption,thereby considerably increasing the intrinsic activity of the doped catalyst for the HER compared with that observed from pristine MoS_(2).The enhanced catalytic activity of P-doped MoS_(2)for the OER is attributed to the ability of the doped P which facilitates the adsorption of hydroxyl and hydroperoxy intermediates and reduces the reaction energy barrier.This study provides a new environmentally friendly and convenient solid-phase ion exchange method to improve the electrocatalytic capability of two-dimensional transition-metal dichalcogenides in largescale applications.

Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting

A low-cost,highly efficient and strong durable bifunctional electrocatalyst is crucial for electrochemical overall water splitting.In this paper,a self-templated strategy combined with in-situ phosphorization is applied to construct hollow structured bimetallic cobalt-nickel phosphide(CoNiP_(x))nanocages.Owing to their unique hollow structure and bimetallic synergistic effects,the as-synthesized CoNiP_(x)hollow nanocages exhibit a high electrocatalytic activity and stability towards hydrogen evolution reaction in all-pH electrolyte and a remarkable electrochemical performance for oxygen evolution reaction in 1.0 mol L^(-1)KOH.Meanwhile,with the bifunctional electrocatalyst in both anode and cathode for overall water splitting,a low voltage of 1.61 V and superior stability are achieved at a current density of 20 mA cm^(-2).

Structure-induced hollow Co3O4 nanoparticles with rich oxygen vacancies for efficient CO oxidation

Co3O4 has been considered as one kind of promising catalysts for the oxidation of CO. According to the Mars-van Krevelen mechanism, oxygen vacancies of Co3O4 play a significant role in catalytic activity. Herein, we report a novel structure-induced strategy to develop hollow Co3O4 with rich oxygen vacancies for efficient oxidation of CO. Through a reduction-oxidation pyrolysis process, the metal-organic frameworks(MOFs) precursor(i.e., ZIF-67) is transformed into H-Co3O4@H-C, in which hollow Co3O4(H-Co3O4) nanoparticles(NPs) are embedded in hollow carbon(H-C) shell.The hollow Co3O4 NPs feature rich oxygen vacancies and finish a complete conversion of CO at 130°C, which is much lower than that of solid Co3O4(the temperature of full CO conversion T100=220°C). Besides, the hollow carbon shell could also reduce the diffusion resistance during the oxidation process. Benefiting from the unique hollow structures,H-Co3O4@H-C even shows comparable activity to noble metal catalysts under high weight hourly space velocities(WHSVs)up to 240,000 mL h^–1 gcat.^–1. Furthermore, the H-Co3O4@H-C catalyst also shows good durability with only a slight decline after the reaction has been operated for 24 h.

Electronic structure evolutions driven by oxygen vacancy in SrCoO3-x films

Ionic defects, such as oxygen vacancies, play a crucial role in the magnetic and electronic states of transition metal oxides. Control of oxygen vacancy is beneficial to the technological applications, such as catalysis and energy conversion. Here, we investigate the electronic structure of SrCoO3-x as a function of oxygen content(x). We found that the hybridization extent between Co 3d and O 2p increased with the reduction of oxygen vacancies. The valence band maximum of SrCoO2.5+δ has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co3+ to an intermediate spin Co4+, resulting in a transition of SrCoO3-x from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO3-x not only illustrate a spin state transition of Co ions,but also indicate a perspective application in catalysis and energy field.