Research progress and development trends in ionic liquid-enhanced electrocatalytic reduction of CO2
Year: 2024
Type: article
Abstract: With the intensification of global climate change and energy crises, finding sustainable and efficient methods to reduce carbon dioxide (CO2) emissions has become a critical challenge. Among various strategies, the electrocatalytic reduction of CO2 (CO2RR) has emerged as a promising approach due to its potential to convert CO2 into valuable chemicals and fuels using renewable electricity. This process not only aids in mitigating CO2 emissions but also contributes to closing the carbon cycle, thus supporting the transition to a low-carbon economy. One of the key challenges in CO2RR is the development of effective catalysts and electrolytes that can enhance the reaction efficiency and selectivity. Ionic liquids (ILs) have attracted considerable attention due to their advantageous characteristics, such as high CO2 solubility, excellent ionic conductivity, wide electrochemical windows, and tunable chemical structures, making them highly suitable for CO2RR applications. Recent research has demonstrated that ILs can serve both as electrolytes and components of the catalytic system. As electrolytes, ILs are capable of dissolving substantial amounts of CO2, which facilitates its availability at the catalytic sites, thereby enhancing the overall reaction rate. Furthermore, the high ionic conductivity of ILs ensures efficient charge transfer during the electrochemical process, while their wide electrochemical window allows for the application of higher potentials without decomposition, enabling the exploration of more efficient catalytic reactions. As components of the catalytic system, ILs interact with CO2 and the catalyst surface, modifying the local environment and influencing the reaction pathways. For instance, ILs can stabilize intermediate species, reduce the activation energy for CO2 reduction, and improve the selectivity towards desired products such as CO, CH4, and C2+ compounds. This dual functionality of ILs has been a focus of intensive research, leading to significant advancements in understanding the underlying mechanisms and optimizing the reaction conditions. This review summarizes the latest research progress on the application of ILs in the field of CO2RR, focusing on their dual roles as electrolytes and catalyst active components. First, when ILs are used as electrolytes, they can be employed alone or mixed with organic solvents or water to form mixed electrolytes. IL electrolytes are particularly effective in promoting the production of C1 products, such as CO and HCOOH. They achieve this by not only activating CO2 molecules to promote reduction reactions but also by altering the electrochemical double layer structure, increasing CO2 adsorption, and improving electrode wettability, which in turn enhances product selectivity and current density. For improving the selectivity of C2 products, such as C2H4 and H2C2O4, IL electrolytes also play a crucial role. By selecting the appropriate type of IL and its compounding ratio, it is possible to finely control the reaction path, thereby increasing the yield and selectivity of the target product. Second, ILs, as active components of catalysts, can be integrated with catalysts through surface modification or can form polymeric ILs that combine with catalysts to create composite structures. These structures provide adsorption active sites for intermediates generated during the catalytic process, enrich CO2 molecules, lower the reduction overpotential, and promote carbon-carbon coupling. Key findings from recent studies are highlighted, including the effects of ILs on the generation and stabilization of reactive species, the modification of reaction pathways, and the enhancement of product selectivity. Despite significant progress, challenges remain in improving reaction efficiency and achieving large-scale industrial application. Based on the current state of research on ILs, several research trends for IL-enhanced CO2RR have been proposed, highlighting future directions for the field.
DOI: 10.1360/tb-2024-0606
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4402158478