A Review of the Use of Immobilized Ionic Liquids in the Electrochemical Conversion of CO 2 (original) (raw)
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Communications Chemistry
The development of efficient CO2 capture and utilization technologies driven by renewable energy sources is mandatory to reduce the impact of climate change. Herein, seven imidazolium-based ionic liquids (ILs) with different anions and cations were tested as catholytes for the CO2 electrocatalytic reduction to CO over Ag electrode. Relevant activity and stability, but different selectivities for CO2 reduction or the side H2 evolution were observed. Density functional theory results show that depending on the IL anions the CO2 is captured or converted. Acetate anions (being strong Lewis bases) enhance CO2 capture and H2 evolution, while fluorinated anions (being weaker Lewis bases) favour the CO2 electroreduction. Differently from the hydrolytically unstable 1-butyl-3-methylimidazolium tetrafluoroborate, 1-Butyl-3-Methylimidazolium Triflate was the most promising IL, showing the highest Faradaic efficiency to CO (>95%), and up to 8 h of stable operation at high current rates (−20 ...
Molecules, 2021
The electrochemical reduction of carbon dioxide (CO2ER) is amongst one the most promising technologies to reduce greenhouse gas emissions since carbon dioxide (CO2) can be converted to value-added products. Moreover, the possibility of using a renewable source of energy makes this process environmentally compelling. CO2ER in ionic liquids (ILs) has recently attracted attention due to its unique properties in reducing overpotential and raising faradaic efficiency. The current literature on CO2ER mainly reports on the effect of structures, physical and chemical interactions, acidity, and the electrode–electrolyte interface region on the reaction mechanism. However, in this work, new insights are presented for the CO2ER reaction mechanism that are based on the molecular interactions of the ILs and their physicochemical properties. This new insight will open possibilities for the utilization of new types of ionic liquids. Additionally, the roles of anions, cations, and the electrodes in...
Ionic liquids for CO2 electrochemical reduction
Chinese Journal of Chemical Engineering, 2020
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Journal of the Brazilian Chemical Society, 2014
Embora tecnologias de captura e armazenamento de carbono (CCS) estejam recebendo grande atenção para a mitigação do efeito estufa, ainda existem muitas desvantagens, tais como o aumento dos custos e gastos de energia associados à sua implementação. No entanto, o uso de CO 2 como bloco de construção C1 em síntese orgânica pode ser muito atraente para o desenho de processos ecológicos. Neste trabalho, foram estudados a sorção de CO 2 e atividades catalíticas de alguns líquidos iônicos (ILs) base imidazólio para síntese de carbonato cíclico. O trabalho demonstra que a presença de um grupo nucleófilo no sistema catalítico pode melhorar seu desempenho, através da utilização de um IL com ânion halogenado ou por mistura de co-catalisador halogenado com ILs. A última abordagem permitiu a obtenção de um sistema de captura de CO 2 eficaz, constituída por IL fluorado mais ZnBr 2 que realiza a síntese de carbonato cíclico com 90% de rendimento e 82% de seletividade. Although the carbon capture and storage (CCS) technologies are receiving great attention for mitigation of greenhouse gas effect, the increasing costs and energy penalties associated to its implementation are still major drawbacks. However, the use of CO 2 as a C1 building block in organic synthesis can be very attractive for the design of environmentally friendly processes. In this work, we have studied both the CO 2 sorption and catalytic activities of some imidazolium based ionic liquids (ILs) for cyclic carbonate synthesis. The work demonstrates that the presence of a nucleophilic group in the catalytic system can enhance its performance by the use of an IL with a halide anion or by mixing a halide co-catalyst with ILs. The latter approach allowed to obtain an effective system for CO 2 capture constituted by a fluorinated IL plus ZnBr 2 that performs cyclic carbonate synthesis with 90% yield and 82% of selectivity.
Chapter 14 -Ionic liquid-mediated CO2 conversion
Ionic Liquid-Based Technologies for Environmental Sustainability, 2022
The catalytic conversion of carbon dioxide (CO2) to value-added products, such as fuels and chemicals, is an important aspect of sustainable energy conversion and storage. However, the efficiency of CO2 conversion and its selectivity toward a specific product has been proved to be challenging due to the chemical inertness and high energy required for CO2 conversion processes. Several aqueous and nonaqueous catalysts have been designed for the purpose of CO2 conversion. Ionic liquids have affinity for CO2 absorption and have recently received attention for their use as solvents, activating agents, electrolytes, and recyclable cocatalysts in CO2 conversion reactions due to their unique molecular structure and properties. Ionic liquids have been found to be active agents in catalyst systems employed in the thermochemical, electrochemical, and photochemical conversion of CO2 to fuels and valuable chemicals. This chapter particularly serves to highlight the important interaction between ILs and CO2, as well as provide an understanding of the role of ionic liquids as mediators in the conversion of CO2 via thermochemical, electrochemical, and photochemical conversion reactions.
CO2 Electroreduction in Ionic Liquids
Frontiers in Chemistry, 2019
CO 2 electroreduction is among the most promising approaches used to transform this greenhouse gas into useful fuels and chemicals. Ionic liquids (ILs) have already proved to be the adequate media for CO 2 dissolution, activation, and stabilization of radical and ionic electrochemical active species in aqueous solutions. In general, IL electrolytes reduce the overpotential, increase the current density, and allow for the modulation of solution pH, driving product selectivity. However, little is known about the main role of these salts in the CO 2 reduction process the assumption that ILs form solvent-separated ions. However, most of the ILs in solution are better described as anisotropic fluids and display properties of an extended cooperative network of supramolecular species. That strongly reflects their mesoscopic and nanoscopic organization, inducing different processes in CO 2 reduction compared to those observed in classical electrolyte solutions. The major aspects concerning the relationship between the structural organization of ILs and the electrochemical reduction of CO 2 will be critically discussed considering selected recent examples.
Principal Descriptors of Ionic Liquid Co-catalysts for the Electrochemical Reduction of CO2
ACS applied energy materials, 2020
Electrochemical reduction of carbon dioxide (CO RR) is promoted by ionic liquid (IL) cocatalysts and several mechanisms have been proposed to explain their role. Due to the complexity of the CO 2 RR, and the limited number of active IL co-catalysts, a consensus on the precise role of ILs has not been reached and it is not possible to improve their activity in a rational way. Herein, we describe guanidinium (Gua) ILs that act as cocatalysts for the CO 2 RR when employed in non-aqueous electrolytes. The peripheral substituents of the Gua cation were systematically modified allowing the IL co-catalytic properties to be fine-tuned, and on the basis of the observed substitution effects, charge delocalization and availability were shown to be the critical descriptors determining cocatalytic activity. These descriptors can be used to rationalize activity trends for other classes of IL co-catalysts.
Journal of Electroanalytical Chemistry, 2021
Carbon dioxide (CO2) plays a key role in controlling the temperature of the Earth. But the increase in the concentration of CO2 in the atmosphere brings with it a series of consequences, originating several environmental problems. The use of electrochemical, spectroscopic and molecular dynamics techniques are useful toolkits to valorize carbon dioxide, and to know the reduction mechanism as a function of CO2 concentration, the cathode nature, and the electrolyte. This manuscript will be mainly centered in the use of ionic liquids (IL) for efficient CO2 capture and valorization into different valuable products thanks to the CO2 electrochemical reduction. In this sense, spectroelectrochemistry based on cyclic voltammetry coupled with Polarization Modulation-Infrared Reflection-Absorption Spectroscopy (PM-IRRAS) and Infrared Reflection-Absorption Spectroscopy (IRRAS) appear to be an efficient instrument to follow the CO2 reactivity in imidazolium ionic liquids. Finally, we present molecular dynamics paired with cyclic voltammetry in order to calculate the diffusion coefficient of CO2 and the number of electrons involved in its reduction process, respectively. Therefore, the current research opens the door to the use of theoreticalexperimental approaches altogether to determine how is the CO2 reduction mechanism. The CO2 reduction products in function of the solvent and nature of the cathode is suggested, proving that the product obtained from the electrochemical reduction of CO2 depends on the electrode material and the solvent.