常温常压高效电化学合成氨催化体系的设计新策略

<正>氨是一种重要的生产原料。除传统工农业用途之外,氨还具有含氢量高(质量比达17.6%)、易液化、易储运等优点。若能实现绿色高效合成氨,势必能为其作为清洁储氢、储能材料等重要应用提供基础。目前,工业上广泛采用的Haber-Bosch方法需要在高温高压(300–500°C,100–200 atm (1atm=100 kPa))等苛刻条件下促进氮分子的活化。其能量和氢气都来自于化石燃料(如甲烷等),因而消耗大量的化石能源,并造成大量的二氧化碳排     

Electrocatalytic Synthesis of Ammonia at Room Temperature and Atmospheric Pressure from Water and Nitrogen on a Carbon‐Nanotube‐Based Electrocatalyst

Ammonia is synthesized directly from water and N₂ at room temperature and atmospheric pressure in a flow electrochemical cell operating in gas phase (half‐cell for the NH₃ synthesis). Iron supported on carbon nanotubes (CNTs) was used as the electrocatalyst in this half‐cell. A rate of ammonia formation of 2.2×10⁻³ g m⁻² h⁻¹ was obtained at room temperature and atmospheric pressure in a flow of N₂, with stable behavior for at least 60 h of reaction, under an applied potential of −2.0 V. This value is higher than the rate of ammonia formation obtained using noble metals (Ru/C) under comparable reaction conditions. Furthermore, hydrogen gas with a total Faraday efficiency as high as 95.1 % was obtained. Data also indicate that the active sites in NH₃ electrocatalytic synthesis may be associated to specific carbon sites formed at the interface between iron particles and CNT and able to activate N₂, making it more reactive towards hydrogenation.     

SDC和SSC在低温常压电化学合成氨中的性能研究

用溶胶—凝胶法制备了Ce0.8Sm0.2O2-δ(SDC)和Sm0.5Sr0.5CoO 3-δ（SSC）超细粉体,采用XRD、TEM和SEM等对粉体进行了观察和表征。分别以Ni-SDC和SSC为阴极, 磺化聚砜质子交换膜为电解质, Ni- SDC金属陶瓷为阳极,银-铂网做集流体组成单电池,在25℃～120℃温度范围内研究了其电导率随温度变化关系及在电化学合成氨中的性能。结果表明：在25℃～120℃温度范围内,使用Ni-SDC和SSC为阴极均有氨气生成,而SSC对电化学合成氨的性能优于Ni-SDC, 在80℃时氨产率达到了6.5×10-9 mol•s-1•cm-2。     

固氮酶及合成氨Fe催化剂中N2的络合位

用乙烯为探针研究了固氮酶中Ｎ２的键合位，结果表明，乙烯不能与Ｎ２在固氮酶体系中相竞争，提出Ｎ２在固氮酶中键合位很可能是蛋白键合ＦｅＭｏ－ｃｏ笼内６Ｆｅ位的μρ（η＾２，ε４）ｔ ３Ｆｅ＋１Ｍｏ位的μ４（η＾３，ε）方式，而不是笼口２Ｆｅ位的μ２（η＾２）方式，在合成氨Ｆｅ催化剂中Ｎ２的络事方式可能是μ６（η＾３，ε３ ）。     

Radiolytic Approach for Efficient,Selective and Catalyst-free CO2 Conversion at Room Temperature

The present study proposes a new approach for direct CO₂ conversion using primary radicals from water irradiation. In order to ensure reduction of CO₂ into CO₂^−. by all the primary radiation-induced water radicals, we use formate ions to scavenge simultaneously the parent oxidizing radicals H^. and OH^. producing the same transient CO₂^−. radicals. Conditions are optimized to obtain the highest conversion yield of CO₂. The goal is achieved under mild conditions of room temperature, neutral pH and 1 atm of CO₂ pressure. All the available radicals are exploited for selectively converting CO₂ into oxalate that is accompanied by H₂ evolution. The mechanism presented accounts for the results and also sheds light on the data in the literature. The radiolytic approach is a mild and scalable route of direct CO₂ capture at the source in industry and the products, oxalate salt and H₂, can be easily separated.     

CO2和N2电还原中缺陷及界面工程的最新进展

实现碳氮循环是人类社会发展的迫切要求,也是催化领域的热门研究课题。在可再生能源的推动下,电催化技术引起了人们的广泛关注,且可以通过改变反应电压获得不同的目标产品。基于此,电催化技术被认为是缓解当前能源危机和环境问题的有效策略,对实现碳中和具有重要意义。其中,电催化CO₂还原反应(CO₂RR)和N₂还原反应(N₂RR)是一种有前途的小分子转化策略。然而,CO₂和N₂均为线性分子,其中C＝O和N≡N键的高解离能导致了它们高的化学惰性。此外,最高占据分子轨道(HOMO)和最低未占分子轨道(LUMO)之间的巨大能量间隙使它们具有高的化学稳定性;且CO₂和N₂的低质子亲和力使它们难以被直接质子化。另一方面,由于CO₂RR和N₂RR与析氢反应(HER)具有相近的氧化还原电位,造成其与HER之间存在竞争性关系,这也是致使催化剂在CO₂RR和N₂RR转化效率低的重要影响因素。因此,CO₂RR和N₂RR仍然面临着过电位高及法拉第效率低等问题。为了克服这些瓶颈,人们为提升CO₂RR和N₂RR电催化剂性能做出了很多努力。众所周知,电催化过程发生在催化剂表面,主要涉及质量传递和电子转移等过程。由此可见,催化剂的性能与其质量和电子传输能力密切相关,而调控催化剂表面结构可以优化活性点的质量和电子转移行为。电催化剂的缺陷和界面工程可通过表面原子工程来实现电子结构调控,对于提高气体吸附能力、抑制HER、富集气体及稳定中间产物等具有重要意义。到目前为止,所报道的各种缺陷和复合电催化剂在提高CO₂RR和N₂RR催化性能等方面均表现出巨大的潜力。在此,我们综述了CO₂RR和N₂RR中催化剂缺陷工程及界面工程的最新进展;首先讨论了四种不同的缺陷(空位、高指数晶面、晶格应变和晶格无序)对CO₂RR和N₂RR性能的影响;然后,总结了界面工程在聚合物-无机复合材料催化剂中的重要作用,并给出了典型实例;最后,展望了原子级电催化剂工程的发展前景,提出了开发和设计高效CO₂RR和N₂RR电催化剂的未来发展方向。     

Thiophene-Containing Covalent Organic Frameworks for Overall Photocatalytic H2O2 Synthesis in Water and Seawater

H₂O₂ is a significant chemical widely utilized in the environmental and industrial fields, with growing global demand. Without sacrificial agents, simultaneous photocatalyzed H₂O₂ synthesis through the oxygen reduction reaction (ORR) and water oxidation reaction (WOR) dual channels from seawater is green and sustainable but still challenging. Herein, two novel thiophene-containing covalent organic frameworks (TD-COF and TT-COF) were first constructed and served as catalysts for H₂O₂ synthesis via indirect 2e⁻ ORR and direct 2e⁻ WOR channels. The photocatalytic H₂O₂ production performance can be regulated by adjusting the N-heterocycle modules (pyridine and triazine) in COFs. Notably, with no sacrificial agents, just using air and water as raw materials, TD-COF exhibited high H₂O₂ production yields of 4060 μmol h⁻¹ g⁻¹ and 3364 μmol h⁻¹ g⁻¹ in deionized water and natural seawater, respectively. Further computational mechanism studies revealed that the thiophene was the primary photoreduction unit for ORR, while the benzene ring (linked to the thiophene by the imine bond) was the central photooxidation unit for WOR. The current work exploits thiophene-containing COFs for overall photocatalytic H₂O₂ synthesis via ORR and WOR dual channels and provides fresh insight into creating innovative catalysts for photocatalyzing H₂O₂ synthesis.     

室温下电化学活化CO2与环氧化合物反应合成环碳酸酯

室温下用铝为牺牲阳极, 以四丁基溴化铵/N,N-二甲基甲酰胺作电解质溶液, 在无隔膜电解池中电化学活化CO₂, 与环氧化合物反应, 合成了环状碳酸酯. 考察了不同电极材料、导电盐、CO₂的压力以及溶剂等因素对电合成结果的影响, 结果表明以Pt为阴极, 在0.05 mol•L^－1 Bu₄NBr/DMF电解质溶液中和4 MPa CO₂下, 环状碳酸酯产率可高达65%～98%.     

Synthesis of the Ruthenium Nitrosyl Complex with Coordinated Ammonia and Pyridine at Room Temperature

The reaction of nitrate ruthenium complex, fac-[RuNO(NH₃)₂(NO₃)₃], with pyridine resulted in cis-[RuNO(NH₃)₂Py₂(NO₃)](NO₃)₂ · H₂O with 84 % yield of the product at room temperature. Addition of any solvent leads to the reaction failure; the excess of pyridine fulfilled the role of a solvent. The DFT simulation of the dissociative mechanism reveals that the nitrate loss from cis-position to NO occurs more easily than for trans-coordinated nitrate. This conclusion is in agreement with the X-ray determined structure of the product. In the solid state, the nitrosyl groups of two neighboring complexes are closely positioned to each other. The small available volume around the nitrosyl group, ca. 0.5 ų, leads to the enhanced stability of the photoinduced metastable state. The Ru–ON isomer converts back to the ground N-coordinated state with 0.001 s^–1 rate constant at 257 K. This O-coordinated isomer of the studied complex is one of the ten known most stable Ru–ON isomers ranked by the “decay” temperature.     

Hydrogenations at Room Temperature and Atmospheric Pressure with Mesoionic Carbene‐Stabilized Borenium Catalysts

1,2,3‐Triazolylidene‐based mesoionic carbene boranes have been synthesized in a convenient one‐pot protocol from the corresponding 1,2,3‐triazolium salts, base, and borane. Borenium ions are obtained by hydride abstraction and serve as catalysts in mild hydrogenation reactions of imines and unsaturated N‐heterocycles at ambient pressure and temperature.     

Visible Light Promoted Iron-Catalyzed One-Pot Synthesis of 2-Arylimino-2H-Chromenes from 2-Hydroxybenzyl Alcohols and β- Ketothioamides at Room Temperature

An efficient, environmentally benign and one-pot approach for the synthesis of 2-arylimino-2H-chromenes from 2-hydroxybenzyl alcohols and β-ketothioamides at room temperature under visible light has been developed. The reported reaction conditions were favorable for a wide range of β-ketothioamides afforded good to excellent yields of the respective products. The low cost and air stable Knölker iron catalyst has been employed for the dehydrogenation of 2-hydroxybenzyl alcohols under photolysis that would usually require a higher temperature.     

SrCe_(0.95)Y_(0.05)O_3-δ在中温区的电化学性质及其在常压合成氨中的应用

SrCe0.95Y0.05O3-δ是一种高温质子导体，本研究采用溶胶—凝胶法合成了 SrCe0.95Y0.05O3-δ纳米粉体，并以该粉体烧制得固体复合氧化物电解质陶瓷，测 定了其在中温区间(400-600℃)的电导率，结果表明不同气氛对其电导率有很大影 响．用该陶瓷在固态质子传导电他中常压下以氮气和氢气为原料合成了氨，并研究 了影响氨合成的关键因素，确定了合适的工作温度，在常压下480℃时氨的产率可 达10^-9mol/(s.cm^-2)以上．     

N,2-二芳基二氮亚烯甲酰胺合成的新方法

偶氮化合物可用作非线性光学材料、激光盘信息存贮材料和现代科技中的油溶性染料［１］．传统偶氮化合物的制备有重氮盐偶合和取代肼氧化等许多方法［２～４］,其偶氮基两端一般联有烃基或芳环,而联有羰基的偶氮类化合物用通常方法难以制备．本文首次用Ｎ－溴代丁二酰亚...     

Polyaniline/SiO2 Nanocomposite Catalyzed Efficient Synthesis of Quinoxaline Derivatives at Room Temperature

Polyaniline/SiO₂ nanocomposite material has been synthesized by using chemical oxidative method. Prepared catalytic material was characterized by means of transmission electron microscopy (TEM), thermal analysis (TG‐DTA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT‐IR). Solvent stability for the catalyst has been screened using UV‐Visible spectroscopy. Polyaniline/SiO₂ catalyzed route has found to be an efficient and rapid protocol for the synthesis of quinoxaline derivatives by cyclocondensation of 1,2‐diketones and o‐phenylenediamines at room temperature. This protocol has several advantages such as high yield, good thermal stability, simple work up procedure, non‐toxic, clean, and easy recovery and reusability of the catalytic system.     

A Protic Ionic Liquid Catalyzes CO2 Conversion at Atmospheric Pressure and Room Temperature: Synthesis of Quinazoline‐2,4(1H,3H)‐diones

The chemical fixation of CO₂ under mild reaction conditions is of significance from a sustainable chemistry viewpoint. Herein a CO₂‐reactive protic ionic liquid (PIL), [HDBU⁺][TFE^?], was designed by neutralization of the superbase 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) with a weak proton donor trifluoroethanol (TFE). As a bifunctional catalyst for simultaneously activating CO₂ and the substrate, this PIL displayed excellent performance in catalyzing the reactions of CO₂ with 2‐aminobenzonitriles at atmospheric pressure and room temperature, thus producing a series of quinazoline‐2,4(1H,3H)‐diones in excellent yields.     

室温固相化学反应法合成Cd(OH)2纳米棒

在表面活性剂聚乙二醇(PEG)存在下,利用Cd(Ac)2·2H2O,CdCl2·2.5H2O,3CdSO4·8H2O和CdCO3分别与NaOH在室温下进行固相化学反应,合成了一系列的Cd(OH)2纳米棒,并利用XRD,TEM和SEM对其结构和形貌进行了表征.实验结果表明,表面活性剂PEG在Cd(OH)2纳米棒的形成过程中充当软模板,对产物形貌的控制起到决定作用.利用这种表面活性剂辅助的软模板固相化学反应法合成一维纳米材料,具有简便易行、反应条件温和以及能耗低等优点.     

Numerical Modeling of a He–N2 Capillary Surface Wave Discharge at Atmospheric Pressure

A self-consistent steady-state spatially averaged collisional-radiativemodel in which the rate coefficients involving electrons are calculatedfrom the solution to the electron Boltzmann equation has been developedfor describing an atmospheric pressure plasma in helium–nitrogen(He–N₂) mixtures. The influence of small nitrogenconcentrations (typically less than 1%) on the discharge characteristicsis studied and compared with available experimental data. It is foundthat nitrogen is highly dissociated and that the density of metastablehelium atoms is considerably reduced by the presence of nitrogen, evenat such low concentrations.     

Room‐Temperature Functionalization of N2 to Borylamine at a Molybdenum Complex

Intermolecular, stepwise functionalization by BH bonds of a (triphosphine)Mo^IV–nitrido complex generated by N₂ splitting is reported. The imido–hydride and di‐hydride–amido Mo^IV complexes have been isolated and characterized. Addition of PinBH to the [Mo(H)₂(N(BPin)₂)]⁺ complex at room temperature results in the liberation of borylamines from the metal center.     

以EDTANa2为矿化剂近中性条件下室温合成介孔二氧化硅

利用EDTANa2作为矿化剂, 在近中性条件下于室温合成了厚壁(约3 nm)蠕虫介孔分子筛. 在反应物配比为n(CTAB):n(TEOS):n(EDTANa2):n(H2O)=(0.05~0.2):(0.1~2):(0.1~0.5):(100~500)范围内都能得到介孔二氧化硅. 以XRD、N2吸附、FTIR、SEM和TEM详细考察了体系配比和温度对介孔二氧化硅结构和形貌的影响, 发现CTAB用量越大, 介孔d值相应增大. 温度对介孔二氧化硅的结构和形貌有很大的影响, 温度在2~15 ℃范围内都能生成孔径分布较规则的介孔, 介孔材料的形貌随温度的升高由空心管变成小颗粒聚集体; 合成的介孔分子筛中的模板剂可以通过乙醇萃取的方式除去. 提出了介孔的生成遵从(S+-E-)0-I0中性模板机理.