Electrochemical Reduction of Benzoylformic Acid in Ionic Liquid

Ionic Hquids possess a number of unique properties that makethem ideal electrolytes. Electrochical reduction of benzoyl-formic acid in room temperature ionic liquids as reaction media could be conducted with excellent performances without any ad-ditional supporting electrolyte. Electrolysis at glassy carbon electrode results in the formation of mandelic acid in 91% yield. And the electrochemical behavior of benzoylformic acid was investigated with the technique of cyclic voltammetry.     

不同离子液体中硝基苯的电化学还原

研究了硝基苯在N-甲基咪唑对甲基苯磺酸([Mim][PhSO3])和1-丁基-3-甲基咪唑六氟磷酸([Bmim][PF6])两种离子液体中的电化学还原反应.循环伏安法测试显示,硝基苯在[Mim][PhSO3]中只出现一个还原峰,是一个受扩散控制的不可逆电化学反应,而在[Bmim][PF6]中出现两对氧化还原峰,表明其还原产物随离子液体性质的不同而异.     

High Performance Fe Porphyrin/Ionic Liquid Co‐catalyst for Electrochemical CO2 Reduction

The efficient and selective catalytic reduction of CO₂ is a highly promising process for both of the storage of renewable energy as well as the production of valuable chemical feedstocks. In this work, we show that the addition of an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate, in an aprotic electrolyte containing a proton source and FeTPP, promotes the in situ formation of the [Fe⁰TPP]^2? homogeneous catalyst at a less negative potential, resulting in lower overpotentials for the CO₂ reduction (670 mV) and increased kinetics of electron transfer. This co‐catalysis exhibits high Faradaic efficiency for CO production (93 %) and turnover number (2 740 000 after 4 hour electrolysis), with a four‐fold increase in turnover frequency (TOF) when compared with the standard system without the ionic liquid.     

Enhanced Photocatalytic Reduction of CO2 to CO through TiO2 Passivation of InP in Ionic Liquids

A robust and reliable method for improving the photocatalytic performance of InP, which is one of the best known materials for solar photoconversion (i.e., solar cells). In this article, we report substantial improvements (up to 18×) in the photocatalytic yields for CO₂ reduction to CO through the surface passivation of InP with TiO₂ deposited by atomic layer deposition (ALD). Here, the main mechanisms of enhancement are the introduction of catalytically active sites and the formation of a pn‐junction. Photoelectrochemical reactions were carried out in a nonaqueous solution consisting of ionic liquid, 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM]BF₄), dissolved in acetonitrile, which enables CO₂ reduction with a Faradaic efficiency of 99 % at an underpotential of +0.78 V. While the photocatalytic yield increases with the addition of the TiO₂ layer, a corresponding drop in the photoluminescence intensity indicates the presence of catalytically active sites, which cause an increase in the electron‐hole pair recombination rate. NMR spectra show that the [EMIM]⁺ ions in solution form an intermediate complex with CO₂^?, thus lowering the energy barrier of this reaction.     

Probing CO2 Reduction Pathways for Copper Catalysis Using an Ionic Liquid as a Chemical Trapping Agent

The key to fully leveraging the potential of the electrochemical CO₂ reduction reaction (CO2RR) to achieve a sustainable solar‐power‐based economy is the development of high‐performance electrocatalysts. The development process relies heavily on trial and error methods due to poor mechanistic understanding of the reaction. Demonstrated here is that ionic liquids (ILs) can be employed as a chemical trapping agent to probe CO2RR mechanistic pathways. This method is implemented by introducing a small amount of an IL ([BMIm][NTf₂]) to a copper foam catalyst, on which a wide range of CO2RR products, including formate, CO, alcohols, and hydrocarbons, can be produced. The IL can selectively suppress the formation of ethylene, ethanol and n‐propanol while having little impact on others. Thus, reaction networks leading to various products can be disentangled. The results shed new light on the mechanistic understanding of the CO2RR, and provide guidelines for modulating the CO2RR properties. Chemical trapping using an IL adds to the toolbox to deduce the mechanistic understanding of electrocatalysis and could be applied to other reactions as well.     

Spontaneous Formation of Nano-Emulsions Containing Task-Special Ionic Liquid and CO2 Capture in this Nano-Emulsions System

Nano-emulsions containing task-special ionic liquid ([NH₂ebim][PF₆]) were prepared by spontaneous emulsification. The stability of nano-emulsions was investigated by analysis of droplet size. The microstructure of the mixed solvent including the Triton X-100, n-butanol, and [NH₂ebim][PF₆] was demonstrated based on macular dynamic simulation. The results indicate that nano-emulsions are relatively stable to the droplet growth at static storage, but unstable under high centrifugal force. Simulation results from the macular dynamic calculation show that [NH₂ebim][PF₆] locates in the hydrophobic layer of Triton X-100 and n-butanol, which is available for enhancing CO₂ mass transfer in an absorption process. Nano-emulsions were used as the absorbent to absorb CO₂ in absorption experiments, and the absorption rates were investigated. The results show that nano-emulsion containing [NH₂ebim][PF₆] can enhance CO₂ absorption rate compared to the system that pure water was used as the absorbent. The reason is attributed to the reversible chemical reaction between [NH₂ebim][PF₆] and CO₂ on the interface of oil and water, which decreases the concentration of CO₂ in the bulk so as to increase the mass transfer driving force between gas and liquid. Therefore, the chemical reaction on the interface of oil and water promotes the absorption process.     

在离子液体中电化学还原合成2-氨基苯甲醚

利用循环伏安法研究了2-硝基苯甲醚在离子液体中的电化学还原行为。以Cu为工作电极,石墨电极为对电极,饱和甘汞电极(SCE)为参比电极,在室温离子液体中电化学还原2-硝基苯甲醚合成2-氨基苯甲醚。优化了电解实验条件,在最佳实验条件(E= -1.0 V, T=50 ℃, c=74.4 mmol·L-1, Q=6 F·mol-1, Y=10:1)下2-氨基苯甲醚的产率最高可达51.3%。在离子液体中电化学合成2-氨基苯甲醚,反应条件温和,避免了有毒易挥发的溶剂、催化剂及其他支持电解质等的使用;并实现了离子液体的重复利用,为2-氨基苯甲醚提供了一条新的绿色化合成路线。     

电解液调控CO2电催化还原性能微观机制的研究进展

二氧化碳(CO₂)排放导致了严重的温室效应, 但作为重要的碳资源, CO₂电催化还原合成化学品因反应条件温和、 反应产物可调及可有效利用分布式电能等优势而备受关注. 在该反应体系中, 电解液作为反应介质, 可提供质子和反应微环境, 影响分子/离子传输. 因此, 构建新型电解液体系对于提高CO₂电催化还原产物的选择性和电流密度起到重要作用. 本文综合评述了CO₂电催化还原过程中电解液的作用和研究现状, 重点总结了水系电解液中阴阳离子(碱金属阳离子、 卤素离子等)和离子液体电解液对CO₂溶解度、 界面双电层结构(pH值、 电场效应)和中间体稳定性等的影响机制, 揭示了其调控对反应产物的选择性、 电流密度等的影响规律. 最后, 对电解液调控CO₂电催化还原性能的研究进行了展望.     

Influence of Humidity on Electrochemical CO2 Sensors Based on Sol-Gel Processed NASICON with New Compositions

Sol-gel processed NASICON-type with new compositions in the Na₃Zr_2–(x/4)Si_2–x P_1+x O₁₂ system showed an improved sinterability with an increase in the x value. This is attributed to liquid phase sintering. This dense electrolyte system is suitable for the application as gas sensors. The CO₂ gas sensors using highly dense x = 0.667 (sample B) and x = 1.333 (sample C) samples show a stable EMF response in dry atmosphere which is very close to the theoretical value. Although a lower sensitivity and slower response were obtained in humid CO₂ gas, the sensor performance recovered after switching from humid gas to dry gas.     

Reduction of Carbon Dioxide to Formate at Low Overpotential Using a Superbase Ionic Liquid

A new low‐energy pathway is reported for the electrochemical reduction of CO₂ to formate and syngas at low overpotentials, utilizing a reactive ionic liquid as the solvent. The superbasic tetraalkyl phosphonium ionic liquid [P₆₆₆₁₄][124Triz] is able to chemisorb CO₂ through equimolar binding of CO₂ with the 1,2,4‐triazole anion. This chemisorbed CO₂ can be reduced at silver electrodes at overpotentials as low as 0.17 V, forming formate. In contrast, physically absorbed CO₂ within the same ionic liquid or in ionic liquids where chemisorption is impossible (such as [P₆₆₆₁₄][NTf₂]) undergoes reduction at significantly increased overpotentials, producing only CO as the product.     

红外光谱电化学研究金电极表面上CO2的还原

以碳酸丙烯酯(PrC)为溶剂,高氯酸四丁基胺(TBAP)为电解质,利用电化学及红外光谱电化学开展了金电极上二氧化碳的还原研究。运用现场红外光谱跟踪电化学还原过程反应物及产物的生成和消失。红外光谱电化学循环伏吸法表明,在消耗CO2的同时,金电极上有CO的产生,且伴随有碳酸根的形成。结合电化学和光谱电化学结果,提出了一种电还原机理:在非水介质中,CO2电还原过程中生成了中间体CO2.-,随后CO2.-分别以两个途径进行还原,其一是直接被还原成CO,其二是与CO2结合生成C2O4.-而后歧化成CO以及CO32-。两个反应同时进行,且第一个反应是可逆过程。     

Polymer-Supported Liquid Layer Electrolyzer Enabled Electrochemical CO2 Reduction to CO with High Energy Efficiency

The electrochemical conversion of carbon dioxide (CO₂) to carbon monoxide (CO) is a favorable approach to reduce CO₂ emission while converting excess sustainable energy to important chemical feedstocks. At high current density (>100 mA cm⁻²), low energy efficiency (EE) and unaffordable cell cost limit the industrial application of conventional CO₂ electrolyzers. Thus, a crucial and urgent task is to design a new type of CO₂ electrolyzer that can work efficiently at high current density. Here we report a polymer-supported liquid layer (PSL) electrolyzer using polypropylene non-woven fabric as a separator between anode and cathode. Ag based cathode was fed with humid CO₂ and potassium hydroxide was fed to earth-abundant NiFe-based anode. In this configuration, the PSL provided high-pH condition for the cathode reaction and reduced the cell resistance, achieving a high full cell EE over 66 % at 100 mA cm⁻².     

离子液体在CO_2电还原反应过程中的催化作用与机理研究

在1-丁基3-甲基咪唑三氟甲基磺酸盐([Bnlim][CF_3SO_3])/碳酸丙烯酯(PC)溶液中,采用循环伏安曲线、交流阻抗谱及阻抗模拟方法,研究了CO_2在Au上发生电还原反应的速率控制步骤与离子液体的催化作用.结果表明,在CO_2电还原反应过程中,吸附态CO_2经单电子还原生成CO_2~-自由基是速率控制步骤.由于离子液体的催化作用,CO_2在[Bmim][CF_3SO_3]/PC溶液中电还原的过电位比在四丁基三氟甲基磺酸铵([Bu_4N][CF_3SO_3])/PC溶液中降低了239 mV.交流阻抗测试结果表明,离子液体中的阳离子[Bmim]~+吸附在Au电极表面,形成离子液体吸附层,吸附态的CO_2分子经单电子还原后生成CO_2~·-)自由基,与周围离子液体发生相互作用,形成中间体[Bmim-CO_2]_(ad),降低了CO_2~(·-)的能量状态,使得CO_2电还原反应的过电位大幅度降低.     

Electrolyte Effects on the Electrochemical Reduction of CO2

The electrochemical reduction of CO₂ to fuels or commodity chemicals is a reaction of high interest for closing the anthropogenic carbon cycle. The role of the electrolyte is of particular interest, as the interplay between the electrocatalytic surface and the electrolyte plays an important role in determining the outcome of the CO₂ reduction reaction. Therefore, insights on electrolyte effects on the electrochemical reduction of CO₂ are pivotal in designing electrochemical devices that are able to efficiently and selectively convert CO₂ into valuable products. Here, we provide an overview of recently obtained insights on electrolyte effects and we discuss how these insights can be used as design parameters for the construction of new electrocatalytic systems.     

关于限域离子液体吸附CO_2的密度泛函理论(DFT)的研究

近年来,温室效应日趋严重,因此吸收CO_2的材料受到了广泛的关注.采用了密度泛函理论(DFT)研究以SiO_2为载体的限域离子液体对CO_2的吸附.对比纯净离子液体(ILs)以及限域离子液体与CO_2的相互作用情况,在这两种状态下两种体系的吸附情况大不相同.从几何结构、相互作用以及电荷分析等方面对ILs、 SiO_2以及ILs/SiO_2复合结构进行研究.计算结果表明,载体、离子液体和CO_2之间都存在较强的相互作用.离子液体的负载不仅改变了SiO_2载体的结构,而且受载体的影响阴阳离子之间的相互作用力也发生了改变.计算结果为进一步深入限域离子液体对CO_2的吸附打下了理论基础.     

Gas-phase and On-surface Chemical Reduction of CO2 to HCHO and CO under Dielectric Barrier Discharge

Selective chemical reduction of CO_2(g) (with carrier Ar) in presence of organic compounds, either mixed in the gas-phase or present as a contact surface, under Dielectric Barrier Discharge is presented in this study. Along with gas-phase CO generation, added hydrocarbons (C _n H _2n+x ; n = 6–12; x = 0 or 2) resulted in HCHO production with the maximum H-atom utilization efficiency being ∼15% of the total present. Product CO and HCHO were estimated separately by pre-concentration in specific absorber solutions followed by their discrete colorimetric measurements. On the other hand, in presence of various types of organic surfaces (e.g. wax, plastics and polymers, also acting simultaneously as a dielectric barrier), it was found that while CO could be estimated as above, in the ensuing chemical conversion, product HCHO was retained on these surfaces. On leaching the HCHO into the absorber solution, its production efficiency was estimated to be ∼5% of CO₂.     

离子液体中固定化光合细菌催化不对称还原反应的研究

采用苯乙酮为模式底物,选用了3种典型的离子液体作为反应介质系统研究了离子液体与缓冲液构成的均相及两相体系中固定化光合细菌催化不对称还原反应的特性．通过对构建的离子液体反应体系进行条件优化,发现与水相及有机相相比,离子液体作为生物催化反应介质更有利于还原反应的进行,并且离子液体及固定化细胞易回收重复利用．研究结果表明,在...     

Oxygen Vacancies in ZnO Nanosheets Enhance CO2 Electrochemical Reduction to CO

As electron transfer to CO₂ is generally considered to be the critical step during the activation of CO₂, it is important to develop approaches to engineer the electronic properties of catalysts to improve their performance in CO₂ electrochemical reduction. Herein, we developed an efficient strategy to facilitate CO₂ activation by introducing oxygen vacancies into electrocatalysts with electronic‐rich surface. ZnO nanosheets rich in oxygen vacancies exhibited a current density of ?16.1 mA cm^?2 with a Faradaic efficiency of 83 % for CO production. Based on density functional theory (DFT) calculations, the introduction of oxygen vacancies increased the charge density of ZnO around the valence band maximum, resulting in the enhanced activation of CO₂. Mechanistic studies further revealed that the enhancement of CO production by introducing oxygen vacancies into ZnO nanosheets originated from the increased binding strength of CO₂ and the eased CO₂ activation.