Preparation of high purity vanadium nitride by magnesiothermic reduction of V2O3 followed by nitriding in N2 atmosphere

High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reaction to get the mixture of V and MgO,and then the products were further nitrided at 1473 K in N2 atmosphere.Finally,the as-prepared samples were acid-leached to obtain pure VN powders.X-ray diffractometry and field-emission scanning electron microscopy were used to analyze the phase transition and morphological evolution of the samples.The results reveal that the overall morphology of the obtained VN powder retains the morphology of the initial V2 O3 powders.After removing MgO by acidic leaching,the porous VN particles can be obtained,with the oxygen content of 0.178 wt.%.Compared with the traditional methods,high purity VN powders with a small amount of oxygen and no carbon can be obtained.

PREPARATION OF ENANTIOMERICALLY PURE SYN-4,5-DIHYDROXY CARBOXYLIC ACID LACTONES BY MICROBIAL REDUCTION

Enantiomerically pure syn-4,5-dihydroxy carboxylic acid lactones were prepared by microbial reduction of acyl lactones with resting cell of Aspergillus niger.

A simple plasma reduction for synthesis of Au and Pd nanoparticles at room temperature

A simple and fast plasma reduction method is developed for synthesis of Au and Pd metal nanoparticles. The scanning electron microscopy(SEM) analysis indicates a formation of aggregates of Au and Pd nanoparticles with branched structure. The transmission electron microscopy(TEM) image shows that the inclusive nanoparticles are all about 5 nm in size. Compared to conventional hydrogen reduction method, plasma method inhibits the agglomeration of metal particles. The room temperature operation is very helpful to limit the nanoparticle size. Most interestingly, plasma reduction produces more flattened metal particles. This plasma reduction does not require the use of any hazardous reducing chemicals, showing the great potential for the fabrication of noble metal nanoparticles.

Catalytic Performance of Ti³⁺Self-Doped V₂O₅-TiO₂Catalysts for Selective Catalytic Reduction with NH₃

Ti3+ self-doping modified V2O5/TiO2 catalyst was prepared by sol-gel and impregnation methods and used for selective catalytic reduction (SCR) of NOx with NH3. Results showed that Ti3+ self-doped V2O5/TiO2 catalyst performed the better catalytic activity. And X-ray diffraction and scanning electron microscopy were used to evaluate the phase composition and morphology of the prepared catalyst. The effects of calcinations temperature of the support, oxygen concentration, [NH3]/[NO] molar ratio and the GHSV on the denitration performance were investigated. It was found that more than 80% NOx conversion was obtained at 210°C when the O2 volume fraction was 5%, the NO concentration was 500 ppm, the [NH3]/[NO] molar ratio = 1 and the GHSV was 23,885 h−1. The results showed that the catalytic activity increased first with the increasing of O2 concentration and [NH3]/[NO] molar ratio, then remained stable. At the same time, the stability of the catalyst was also studied at the temperature of 210°C. The reaction continued for 750 minutes, and the catalytic activity remained above 80%, indicating that the catalyst has a good stability. Moreover, the Ti3+ self-doped V2O5/TiO2 catalyst also showed good SO2 and H2O resistance. Therefore, these findings provide important information to better understand the application of the prepared catalyst.

Hydrogen-assisted scalable preparation of ultrathin Pt shells onto surfactant-free and uniform Pd nanoparticles for highly efficient oxygen reduction reaction in practical fuel cells

Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area(ECSA)for the oxygen reduction reaction(ORR)in hydrogen-based proton-exchange membrane fuel cells.Accordingly,a facile,low-cost,and hydrogen-assisted two-step method is developed in this work,to massively prepare carbon-supported uniform,small-sized,and surfactant-free Pd nanoparticles(NPs)with ultrathin~3-atomic-layer Pt shells(Pd@Pt_(3L) NPs/C).Comprehensive physicochemical characterizations,electrochemical analyses,fuel cell tests,and density functional theory calculations reveal that,benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects,Pd@Pt_(3L) NPs/C exhibits not only significantly enhanced ECSA,electrocatalytic activity,and noble-metal(NM)utilization compared to commercial Pt/C,showing 81.24 m^(2)/gPt,0.710 mA/cm^(2),and 352/577 mA/mgNM/Pt in ECSA,area-,and NM-/Pt-mass-specific activity,respectively;but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test.More importantly,the corresponding 25-cm^(2) H2-air/O_(2) fuel cell with the low cathodic Pt loading of~0.152 mgPt/cm^(2)geo achieves the high power density of 0.962/1.261 W/cm^(2)geo at the current density of only 1,600 mA/cm^(2)geo,which is much higher than that for the commercial Pt/C.This work not only develops a high-performance and practical Pt-based ORR electrocatalyst,but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure,which can be further expanded to other metal shells for other energy-conversion applications.

Bulk preparation of free-standing single-iron-atom catalysts directly as the air electrodes for high-performance zinc-air batteries

The keen interest in fuel cells and metal-air batteries stimulates a great deal of research on the development of a cost-efficient and high-performance catalyst as an alternative to traditional Pt to boost the sluggish oxygen reduction reaction(ORR)at the cathode.Herein,we report a facile and scalable strategy for the large-scale preparation of a free-standing and flexible porous atomically dispersed Fe-N-doped carbon microtube(FeSAC/PCMT)sponge.Benefiting from its unique structure that greatly facilitates the catalytic kinetics,mass transport,and electron transfer,our FeSAC/PCMT electrode exhibits excellent performance with an ORR potential of 0.942 V at^(-3) mA cm^(-2).When the FeSAC/PCMT sponge was directly used as an oxygen electrode for liquid-state and flexible solid-state zinc-air batteries,high peak power densities of 183.1 and 58.0 mW cm^(-2) were respectively achieved,better than its powdery counterpart and commercial Pt/C catalyst.Experimental and theoretical investigation results demonstrate that such ultrahigh ORR performance can be attributed to atomically dispersed Fe-N_(5) species in FeSAC/PCMT.This study presents a cost-effective and scalable strategy for the fabrication of highly efficient and flexible oxygen electrodes,provides a significant new insight into the catalytic mechanisms,and helps to realize significant advances in energy devices.

Pt‑Based Intermetallic Compound Catalysts for the Oxygen Reduction Reaction:Structural Control at the Atomic Scale to Achieve a Win–Win Situation Between Catalytic Activity and Stability

The development of ordered Pt-based intermetallic compounds is an effective way to optimize the electronic characteristics of Pt and its disordered alloys,inhibit the loss of transition metal elements,and prepare fuel cell catalysts with high activity and long-term durability for the oxygen reduction reaction(ORR).This paper reviews the structure–activity characteristics,research advances,problems,and improvements in Pt-based intermetallic compound fuel cell catalysts for the ORR.First,the structural characteristics and performance advantages of Pt-based intermetallic compounds are analyzed and explained.Second,starting with 3d transition metals such as Fe,Co,and Ni,whose research achievements are common,the preparation process and properties of Pt-based intermetallic compound catalysts for the ORR are introduced in detail according to element types.Third,in view of preparation problems,improvements in the preparation processes of Pt-based intermetallic compounds are also summarized in regard to four aspects:coating to control the crystal size,doping to promote ordering transformation,constructing a“Pt skin”to improve performance,and anchoring and confinement to enhance the interaction between the crystal and support.Finally,by analyzing the research status of Pt-based intermetallic compound catalysts for the ORR,prospective research directions are suggested.

A non-precious metal catalyst for oxygen reduction prepared by heat-treating a mechanical mixture of carbon black,melamine and cobalt chloride

A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V （vs. SCE） at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β- cobalt.

Effect of praseodymium additive on CeO2(ZrO2)/TiO2 for selective catalytic reduction of NO by NH3

A series of praseodymium added CeO2（ZrO2）/TiO2 catalysts separately prepared by methods of sol-gel and impregnation were tested for selective catalytic reduction of NO, and characterized by X-ray diffraction （XRD）, N2-brumauer-emmett-teller （N2-BET）, NH3-temperature programmed desorption （NH3-TPD）, H2-temperature programmed reduction （H2-TPR）, PL spectra, Ra-man spectra, electron paramagnetic resonance （EPR） and X-ray photoelectron spectroscopy （XPS）, respectively. Influence of prepara-tion method on catalytic performance was studied. Results showed that the influence of Pr addition on catalytic performance of the CeO2（ZrO2）/TiO2 catalysts was different between the sol-gel method and the impregnation method. The Pr addition tended to interact with TiO2 and formed the structure of Ti-O-Pr in the sol-gel method while it was more likely to interact with CeO2 forming the struc-ture of Ce-O-Pr in the impregnation method. The total acid amount and redox properties of the catalysts prepared by sol-gel method decreased with the addition of Pr element, which resulted in decrease of catalytic activity. In contrast, the Pr-added catalyst prepared by impregnation method was found to possess easier reducibility, more total acid amount and higher proportion of Ce3＋ species, which was favourable for higher catalytic activity.

In situ preparation of well-dispersed CuO nanocatalysts in heavy oil for catalytic aquathermolysis

We developed an in situ synthesis strategy for preparing well-dispersed CuO nanoparticles as aquathermolysis catalyst for viscosity reduction in Shengli heavy oil(China). A Cu(OH)_2-contained microemulsion was employed as a carrier to disperse the precursor Cu(OH)_2 to the heavy oil phase. Under aquathermolysis condition(240 ℃, 2.5 MPa of N_2), the Cu(OH)_2 precursors would first be converted in situ to well-crystallized and size-homogeneous CuO nanoparticles naturally, catalyzed by which the viscosity of Shengli heavy oil could be reduced as much as 94.6%; simultaneously, 22.4% of asphaltenes were converted to light components. The agglomeration of the in situ prepared monoclinic CuO nanoparticles could be negligible throughout the catalytic reaction. Based on the characterization results of ~1 H NMR, elemental analysis and GC-MS of oil samples before and after catalytic aquathermolysis, the mechanism for viscosity reduction of heavy oil in the catalytic system was investigated.

Atomic cobalt anchored on covalent triazine frameworks with ultra-high performance towards oxygen reduction reaction

Single cobalt atom is promising non-precious metal catalyst instead of Pt in the oxygen reduction reaction(ORR).However,it is still a great challenge to develop a costeffective,ultrastable and efficent single-atom cobalt catalyst for ORR,requiring efficient fabrication strategies and robust support to stabilize the single cobalt atom.Here,we prepared a highly active and stable atomically isolated cobalt catalyst via covalent triazine framework(CTF)support with Ketjen Black(KB)hybridization in scale.The prepared single Co catalyst(Co-CTF/KB)possesses high metal loading over 4 wt%and shows superior ORR performance with a half-wave potential(E1/2)of 0.830 V and a limiting current density of 6.14 mA cm-2 as well as high tolerance of methanol in an alkaline medium,which outperforms commercial Pt/C and most non-precious-metal catalysts reported to date.Benefiting from strong stabilization of Co atoms on CTF,Co-CTF/KB shows outstanding stability with only 5 mV negative shifts after 10,000 cycles.Moreover,it also displays high catalytic activity for oxygen evolution reaction(OER),suggesting it is an efficient ORR/OER bifunctional catalyst.The present work provides a facile strategy for preparing single-atom catalysts in bulk quantity and contributes to development of catalysts for electrochemical conversion and storage devices.

Fabrication of SmCo_(5) alloy via cobalt-induced calciothermic reduction and magnetic properties of its ribbon

SmCo_(5)alloy was prepared via direct calciothermic reduction using anhydrous samarium fluoride(SmF_(3))as raw material and cobalt as inducer.Results of the thermodynamic calculation show that the direct reduction of cobalt-induced SmF_(3)for preparing SmCo_(5)alloy is feasible.An alloy with 33.89 wt%samarium and a yield of 96.45%were achieved under the optimal conditions of 10%and 20%excess of SmF_(3)and calcium over the stoichiometry,respectively,and 1450℃for 4 min.The X-ray diffraction results show that the reduction products are SmCo_(5)alloy and CaF_(2).The scanning electron microscopy micrograph of the SmCo_(5)alloy ingot exhibits a distinct dendritic morphology composed of samarium and cobalt.The X-ray photoelectron spectroscopy shows that the atomic ratio of samarium to cobalt is approximately 1:5 and both elements demonstrate zero valency(Sm^(0),Co^(0)).The magnetic properties measurement of the SmCo_(5)alloy melt-spun ribbon shows the remanent magnetization B_r=0.59 T,intrinsic coercivity H_(Ci)=345.82 kA/m and maximum magnetic energy density(BH)_(max)=42.20 kJ/m^(3).These results may be helpful for the development of novel valence-variable rare-earth alloys.

纳米零价铁的制备及氧化还原技术的应用进展

纳米零价铁(nZVI)因具有强还原能力和高吸附性能等特点,在环境污染修复中应用前景广阔。近年来,国内外学者开发了多种nZVI的合成方法,并在nZVI还原去除有机、无机污染物以及nZVI耦合高级氧化技术方面均有较大进展。本文综述了nZVI的物理、化学和绿色合成制备方法的原理及优缺点,分析了nZVI还原降解、吸附固定等作用去除有机、无机污染物的机制及影响因素,重点探讨了nZVI联用氧化剂(如分子氧、过氧化氢、过氧化钙和过硫酸盐等)构建类芬顿技术的机理及应用进展,并对nZVI修复技术的环境应用进行了展望,以期为nZVI的高效制备和环境修复领域的广泛应用提供参考。

钨粉制备及其对钨合金性能影响的研究进展

金属钨因具有高熔点、高硬度、耐腐蚀、耐磨和热膨胀系数小等优点而被广泛应用于制备各种合金材料。本研究综述了钨粉的制备方法,如熔盐电解法、溶胶凝胶法、高能球磨法和氢气还原法。针对钨粉均匀性问题,重点阐述了目前使用最广泛的氢气还原法的研究现状,其中,调控氢气中水蒸气分压有利于提高钨粉均匀性;气流磨和球化等钨粉的处理工艺有助于提高钨粉均匀性和分散性。另外,介绍了钨粉粒度和分散性等对钨合金性能的影响,均匀分散的钨粉对制备组织均匀的钨合金优势巨大。针对钨粉和钨合金中钨晶粒之间的相关性介绍了晶粒细化的相关研究。简要介绍了钨粉性能对增材制造钨合金性能的影响。

AuAg合金纳米催化剂的制备及应用研究进展

目的纳米Au催化剂一直是多相催化领域的典型研究材料之一,其具有特殊的电子、结构性质及对诸多氧化、还原反应历程的高催化性能。但是纳米Au催化剂存在尺寸依赖性强,对O_(2)等基础物质活化能力弱等问题。Ag与Au形成合金材料则是解决上述问题的重要途径之一。已有研究中采用多种不同的AuAg催化剂制备方法,并且其在不同催化应用中涉及多种催化机理,但未有研究将其制备过程以及协同催化机理进行对比总结。因此,针对AuAg合金催化剂,综述了其常见的制备方法和预处理条件及其在CO氧化等氧化反应、不饱和醛加氢等加氢反应中的应用以及催化反应机制,并提出了未来可能的发展方向。方法通过对AuAg催化剂的研究和应用进行综述,分析了不同制备方法的特点及预处理条件对AuAg催化剂结构的影响以及AuAg催化剂在不同反应中的催化机理。结果在该合金材料的制备和预处理方面,对比了不同制备方法及其对该合金颗粒在载体表面负载状况的影响机制,也深入探讨了预处理条件对AuAg纳米粒子的尺寸及合金化程度的调控作用。在催化应用上,Ag的加入能够改善纳米Au的抗烧结能力,二者间的电子效应也可提升材料对O_(2)等基础物质活化能力,并降低Au颗粒尺寸变化对催化反应结果的影响,最终高效催化CO氧化、醇氧化、不饱和醛加氢、炔烃加氢以及硝基芳香化合物还原等反应历程。结论目前有多种制备AuAg合金纳米催化剂的方法,而其结构的可控及稳定的合成仍是未来的研究重点。同时,AuAg催化剂在不同反应中催化机理的探索对AuAg催化剂的定向设计尤为重要,应进行更深入的研究,以更快实现工业应用。

全产业链贯通布局下钒液流电池长时储能发展思考

清洁能源的发展和“双碳”目标的实施推动了能源结构调整和电网系统升级,这必将催生巨大的万亿长时储能需求,麦肯锡预测2030年全球可再生能源占比将升至60%~70%,长时储能比2025年增加5~10倍(预计2025年30~40 GW)。全钒液流电池相比其他电化学储能具有安全长寿、灵活可靠、资源丰富等优点,2018~2023年国家和地方发布了多项清洁能源储能配置标准的政策性文件,在此背景下钒储能电池行业企业持续高速增长,行业集中度提升,宏观领域表现为我国钒储能产业正处在加速发展期。目前,钒储能电池总体成本较高,主要原因是钒原料价格高,降低成本的核心环节是钒资源提取成本和电解液生产制造成本。中国恩菲研发的短流程制备钒电解液技术相对于传统钒电解液制备技术具有流程短、钒利用率高的特点,制造成本降低了30%~50%,后期随着钒资源开发和新工艺的研发成功,钒储能产业降本优势将愈发突出。在国家政策支持下,钒液流电池储能系统有望在短期内实现规模化、商业化应用,成为储能领域的重要选择。未来,钒液流电池储能系统仍需从多方面进行优化,如重视技术创新和研发、健全回收利用体系等,以实现钒液流电池长时储能产业的可持续发展。

分步液相还原法制备六方片状纳米银粉工艺研究

为探究分步液相还原法制备六方片状纳米银粉工艺条件对纳米银粉形貌及粒径的影响,以硝酸银为银源,过氧化氢为氧化刻蚀剂,硼氢化钠、抗坏血酸为还原剂,柠檬酸钠为形貌诱导剂,通过分步液相还原法制备出了六方片状纳米银粉。考察了制备工艺中晶种阶段过氧化氢用量、硼氢化钠用量、生长阶段柠檬酸钠用量、反应溶液pH值等工艺条件对纳米银粉形貌及粒径的影响规律,并分析了其影响机理。结果表明,当晶种阶段过氧化氢与硝酸银摩尔比为50∶1、硼氢化钠与硝酸银摩尔比为2∶1、生长阶段柠檬酸钠与硝酸银摩尔比为2∶1,反应溶液pH=8时,可制备出粒度分布均匀的六方片状纳米银粉,其六边形平均边长为40~60nm。晶种阶段过氧化氢用量是影响纳米银粉形貌的关键因素,随过氧化氢用量增大,纳米银粉形貌发生由类球状到片状的转化,过氧化氢过量可使片状纳米银粉边缘发生刻蚀作用;生长阶段反应溶液酸碱度是影响纳米银粉粒径的关键因素,随反应溶液pH值增大,纳米银粉平均粒径逐渐减小;柠檬酸钠可在纳米银粉表面发生选择性吸附,诱导纳米银粉发生各向异性生长,生成片状结构。

多元醇液相还原法制备银纳米线的研究

银纳米线(AgNWs)因具有高导电性、高透光性及良好的耐弯曲柔性,已成为传统氧化铟锡(ITO)透明导电材料的替代品。采用液相多元醇还原法制备了不同规格的银纳米线,并通过SEM、UV-Vis、XRD等测试手段对制备的银纳米线进行了表征。结果表明,不同的制备参数可以获得颗粒状、短棒状、线状等不同形态的银产物。反应温度160℃,反应体系中聚乙烯吡咯烷(PVP)与AgNO_(3)的摩尔比为2∶1,FeCl_(3)的浓度保持在0.1~0.2mmol/L之间时,可以制备得到长度约30μm、直径约50nm的高纯度银纳米线。

MOFs基材料在电催化还原CO_(2)中的应用

介绍了金属有机框架(MOFs)基材料用于电催化还原CO_(2)(eCO_(2)RR)的研究进展和相关催化剂的制备方法,对比了不同结构MOFs基催化材料在eCO_(2)RR的催化活性、催化稳定性以及产物选择性方面的表现。指出MOFs材料因具有周期性结构的催化活性位点和较高的CO_(2)吸附性能被广泛应用于电催化领域,合理设计高活性、高选择性的CO_(2)还原电催化剂以实现高效的CO_(2)减排,对减少全球温室气体的排放具有重要意义。

银纳米粒的合成及表征

银纳米粒(AgNPs)作为抗菌剂已有悠久的历史,但其抗菌活性受粒径、表面积比、形态以及银离子释放动力学等因素影响,因此制备形貌和尺寸可控且稳定的银纳米粒具有重要意义。文章采用还原法并结合Lee-Meis法,定制化制备4 nm和30 nm的银纳米粒,通过紫外-可见分光光度计、粒径电位分析仪和透射电子显微镜进行表征,而后通过粒径和电位的变化来评估其稳定性。结果表明,粒径均匀、分散性良好的4 nm和30 nm AgNPs,在37℃含10%FBS的培养基中可稳定存在至少7 d。