Efficient CO2 conversion to fuels and chemicals using ionic liquid electrolyte
Researchers discovered that combining ionic liquids electrolytes with metal hydroxides enables efficient electrochemical conversion of CO2 to hydrocarbons
IMAGE:
THE PRODUCTION OF HYDROCARBONS OCCURS THROUGH TWO INTERMEDIATES FORMED ON THE SURFACE OF THE SILVER ELECTRODE TO PRODUCE USEFUL HYDROCARBONS LIKE ETHYLENE, ETHANE, PROPYLENE, AND PROPANE.
view moreCREDIT: TAKUYA GOTO FROM DOSHISHA UNIVERSITY
Converting CO2 into fuel and chemicals using electricity, also known as electrochemical conversion of CO2, is a promising way to reduce emissions. This process allows us to use carbon captured from industries and the atmosphere and turn it into resources that we usually get from fossil fuels.
To advance ongoing research on efficient electrochemical conversion, scientists from Doshisha University have introduced a cost-effective method to produce valuable hydrocarbons from CO2. The study was made available online on 17 May 2024 and formally published in the journal Electrochimica Acta on 20 July 2024. The research team, led by Professor Takuya Goto and including Ms. Saya Nozaki from the Graduate School of Science and Engineering and Dr. Yuta Suzuki from the Harris Science Research Institute, produced ethylene and propane on a basic silver (Ag) electrode by utilizing an ionic liquid containing metal hydroxides as the electrolyte.
“Most studies on CO2 electrolysis with room-temperature liquid electrolyte have focused on the electrode's catalytic properties. In this groundbreaking study, we focused on the electrolyte and succeeded in producing valuable hydrocarbon gas even on a simple metal electrode,” says Prof. Goto.
Ionic liquids offer unique advantages for the electrochemical reduction of CO2. They operate over a wide range of voltages without decomposing, are non-flammable, and have high boiling points. This stability enables the electrolyte to withstand the high temperatures generated during exothermic CO2 reduction.
In their study, researchers investigated the electrochemical conversion of CO2 and water with N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate (DEME-BF4) as the electrolyte. The DEME-BF4 electrolyte provides optimal conditions for maximizing CO2 reduction. DEME+ ions enhance the solubility of CO2, allowing a greater number of CO2 molecules to participate in the reaction. Moreover, due to its hydrophilic nature, the hydrogen ions required for reducing CO2 to hydrocarbons can be easily supplied by mixing the electrolyte with water.
The researchers determined that the electrochemical conversion of CO2 to hydrocarbons could be increased with the addition of aqueous solutions containing metal hydroxides like calcium hydroxide (Ca(OH)2), sodium hydroxide (NaOH), and cesium hydroxide (CsOH) to the electrolyte. The hydroxides in the ionic liquid can react with CO2 to form bicarbonates (HCO3−) and carbonates (CO32−), further enhancing the availability of CO2 to participate in electrochemical reactions.
Under room temperature electrolysis (298 K or 25°C) in a CO2 atmosphere, the researchers successfully reduced CO2 to ethylene (C2H4), ethane (C2H6), propylene (C3H6), and propane (C3H8). They achieved the highest current efficiencies for each product using DEME-BF4 electrolyte mixed with water and containing Ca(OH)2, with efficiencies reaching up to 11.3% for propane and 6.49% for ethylene. This efficiency surpassed those obtained with other metal hydroxides by over 1000 times.
The reason for this high efficiency was explained using Raman spectroscopy and density functional theory (DFT) calculations. These analyses revealed that bicarbonate ions, formed when CO2 interacts with OH- ions in the electrolyte, interact with DEME+ and BF4- ions of the electrolyte to form a stable structure [DEME+-BF4−-HCO3−-Ca2+].
CO2 and HCO3- species then adsorb onto the electrode surface forming adsorbed species CO− ads. The adsorbed CO- ions then strongly interact with Ca2+ ions present in the electrolyte, forming two distinct intermediate structures: One structure A, consisting of a Ca2+ ion coordinated with two CO− ions adsorbed on three Ag atoms, and the other Structure B, where the Ca2+ ion is coordinated with two CO− ions adsorbed on two Ag atoms. This interaction with Ca2+ ions is crucial as it increases the stability of the adsorbed species, making the subsequent electrochemical reactions possible.
Among these structures, researchers suggest that structure B is more stable and is the preferred pathway for ethylene, while structure A leads to the production of propane. “We showed that tailoring the electrolyte can lead to molecular-level changes in the phase transformation of CO2 in bulk solution and at the electrode/ionic liquid electrolyte interface and proposed a process that enables the synthesis of unique hydrocarbons such as C3,” says Prof. Goto.
These findings shed light on the processes involved in the conversion of CO2 at the interface between ionic liquid-based electrolytes and metal electrodes, such as the role of calcium ions. Such insights can help in the development of electrolytes for the efficient production of useful hydrocarbons from CO2. “The physicochemical knowledge of this new route from CO2 decomposition to synthesizing useful hydrocarbons, as revealed in this study, will be instrumental in advancing CO2 utilization technology and contributing to academic progress in materials science.” concludes Prof. Goto.
About Professor Takuya Goto from Doshisha University, Japan
Takuya Goto is a Professor in the Faculty of Science and Engineering, Department of Environmental Systems Science. He specializes in research areas such as Energy/Earth resource engineering, energy science, and electrochemistry. Prof. Goto has published more than 94 papers in scientific journals, on topics that include molten salt electrolysis and the utilization of captured CO2. He received his Doctor of Energy Science degree from Kyoto University. For more information, visit his researcher profile at https://researchmap.jp/takuya_goto
Funding information
This research was partially supported by JSPS KAKENHI Grant Number JP22K14700 and the steel carbon neutrality research grant from The Iron and Steel Institute of Japan.
Media contact:
Organization for Research Initiatives & Development
Doshisha University
Kyotanabe, Kyoto 610-0394, JAPAN
E-mail：jt-ura@mail.doshisha.ac.jp
JOURNAL
Electrochimica Acta
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Electrochemical synthesis of C2 and C3 hydrocarbons from CO2 on an Ag electrode in DEME-BF4 containing H2O and metal hydroxides
Fixing excess carbon dioxide: biocatalyst-driven carboxylation under mild conditions
Researchers achieved carboxylation of an unnatural compound as well as natural one by utilizing Thermoplasma acidophilum malic enzyme
IMAGE:
BIOCATALYTIC CARBOXYLATION BY MALIC ENZYME NEW AVENUES FOR SELECTIVE SYNTHESIS OF WIDER CO2 FIXATION PRODUCTS.
view moreCREDIT: TOKYO INSTITUTE OF TECHNOLOGY
Carbon capture and utilization technologies for the conversion of carbon dioxide into carboxylic acids have garnered attention recently, with researchers from Tokyo Tech recently demonstrating a biocatalyzed carboxylation reaction of not only natural substrate, pyruvate, but also unnatural one, 2-ketoglutarate, using Thermoplasma acidophilum NADP+- malic enzyme under mild reaction conditions. The proposed strategy can be tailored for the selective synthesis through carbon dioxide fixation reactions.
Removing the excess carbon dioxide (CO2) from the environment is not the end goal of the decarbonization process necessary to reduce the effects of global warming caused by the greenhouse gas. Rather, novel carbon capture and utilization (CCU) technologies are gaining popularity in the current decade as an effective method for removing CO2 from the environment and transforming it into something valuable, for instance, commercially used chemicals such as carboxylic acids.
However, the stability of CO2 makes it unreactive and therefore a difficult starting material for carboxylic acid production. Thus, the resulting carboxylation procedure requires reactive reagents, high temperature and pressure conditions which significantly impact the process's energy cost and sustainability.
To overcome these issues, researchers Associate Professor Tomoko Matsuda and master student Yuri Oku, both from the Department of Life Science and Technology at Tokyo Institute of Technology (Tokyo Tech), explored the use of biocatalysts for CO2 fixation reactions. The findings of their study were published online in JACS Au on May 13, 2024. The researchers investigated and performed a carboxylation reaction under mild conditions in the presence of biocatalyst Thermoplasma acidophilum NADP+- malic enzyme (TaME) and gaseous CO2 via coupling enzymatic coenzyme regeneration. The proposed strategy accomplished the carboxylation reaction of not only a natural substrate pyruvate but also an unnatural substrate 2-ketoglutarate.
“The objective of our study was to develop a TaME-catalyzed carboxylation reaction using only gaseous CO2 as a CO2 source and to widen the substrate specificity of TaME for carboxylation,” remarks Matsuda. For the carboxylation reaction, the researchers chose TaME as the enzyme hoping for robustness and ease of handling, similar to other enzymes from T. acidophilum, which were also reported to have high thermal and CO2-pressure stabilities.
For carboxylation of pyruvate, it was treated with TaME and co-enzyme NADPH under 0.1 MPa pressure of CO2. This, however, led to a relatively lower yield. To solve this issue, the researchers added two new co-factors, namely TaGDH (GDH: glucose dehydrogenase) and D-glucose, which resulted in an 18-fold increase in the yield. They also studied the effects of CO2 pressure, pH, and substrate concentration on the carboxylation reaction. Furthermore, they successfully carried out reductive carboxylation of unnatural substrate, 2-ketoglutarate, to the corresponding product isocitrate by gaseous CO2, TaME, and TaGDH and D-glucose.
The biocatalyst-driven strategy proposed in this study led to successful carboxylation of natural substrate, pyruvate, and unnatural one, 2-ketoglutarate, under mild temperature (37 °C) and pressure conditions (0.1 MPa CO2), thus, lowering the energy burden and increasing the sustainability of the entire CCU process. The effective use of TaME has opened new avenues for selective synthesis of wider carboxylation products using safer and more environmentally friendly reagents instead of harsh chemicals.
“We believe that our proposed method can be re-engineered to perform a wide range of selective carboxylation reactions using renewable resources, under milder reaction conditions, and with less unwanted by-products and waste, unlocking the possibility of biocatalysis for the utilization of carbon dioxide as a starting material.” concludes Matsuda.
###
Related Links
For a greener, safer synthetic chemistry | Tokyo Tech story
https://www.titech.ac.jp/english/public-relations/prospective-students/first-step/matsuda-lab
Matsuda Research Group
https://www.matsuda.bio.titech.ac.jp/index(English).html
About Tokyo Institute of Technology
Tokyo Tech stands at the forefront of research and higher education as the leading university for science and technology in Japan. Tokyo Tech researchers excel in fields ranging from materials science to biology, computer science, and physics. Founded in 1881, Tokyo Tech hosts over 10,000 undergraduate and graduate students per year, who develop into scientific leaders and some of the most sought-after engineers in industry. Embodying the Japanese philosophy of “monotsukuri,” meaning “technical ingenuity and innovation,” the Tokyo Tech community strives to contribute to society through high-impact research.
https://www.titech.ac.jp/english/
JOURNAL
JACS Au
METHOD OF RESEARCH
Experimental study
ARTICLE TITLE
Substrate Promiscuity of Thermoplasma acidophilum Malic Enzyme for CO2 Fixation Reaction
Large language model in electrocatalysis
IMAGE:
LARGE LANGUAGE MODEL (LLM), SERVING AS A CONDUIT FOR COMMUNICATION BETWEEN ARTIFICIAL INTELLIGENCE AND HUMANS, CAN BREAK DOWN THE BARRIERS IN THIS INTERACTION. THEY OVERCOME THE LIMITATIONS IMPOSED BY HUMAN’S CONVENTIONAL THINKING, ABSORBING KNOWLEDGE FROM ALL SUBFIELDS OF CATALYSIS WHILE KEEPING UP WITH EFFICIENT DAILY UPDATES IN LITERATURE. THUS, THEY FULLY LEVERAGE HUMANITY'S COLLECTIVE KNOWLEDGE IN CATALYSIS, PAVING A SMOOTH ROAD FOR THE QUEST FOR EFFICIENT CATALYSTS.
view moreCREDIT: CHINESE JOURNAL OF CATALYSIS
Large language models, outstanding representatives of modern technology, have significant impacts on various fields of modern society. These models, constructed by billions of neurons, incorporate the extensive knowledge accumulated by humans so far, possessing the exceptional abilities to chat with people around the world fluently. Their human-like intelligence enables them to tackle various challenges of modern society and shows great potential for applications in various fields.
Recently, a research team led by Prof. Ziyun Wang from the University of Auckland in New Zealand delved into the potential applications of large language models in the field of electrocatalysis. This Perspective aims to elucidate how these AI-driven models help researchers deepen their understanding of catalysis and advance intelligent catalyst design. The work first examined the limitations of traditional experimental methods and multi-scale simulation approaches, such as high resource consumption, slow progress, and the constraints of human capabilities. The study then highlighted the significant advantages of large language models in electrocatalysis research. These models can transcend human cognitive limits and theoretically accumulate unlimited knowledge. Despite their enormous potential, challenges such as balancing generalization and domain specificity, and text limitations remain. To address these challenges, the paper introduced the development of multimodal large language models and their specific applications in electrocatalysis research. These applications include direct interaction with experimenters, continuous optimization based on experimental feedback, fine-tuning of pre-trained models, and multimodal data integration with visual encoders.
The paper emphasized the vast potential of multimodal large language models in areas such as spectral analysis, experimental pathway design, transition state search, molecular structure design, catalyst optimization, and problem diagnosis. In summary, multimodal approaches hold broad application prospects in catalysis, integrating various data sources to provide powerful tools and technical support for catalyst design, reaction mechanism research, and optimization of reaction conditions. This work also discussed large language models' role and future development trends in scientific research. While these models have demonstrated outstanding capabilities in knowledge accumulation, they may still fall short in creating new knowledge compared to scientists. Large language models should be deeply integrated with experimental and simulation methods to enhance their predictive power and multimodal learning capabilities. Such integration will enable large language models to more comprehensively assist researchers, thereby accelerating the development of scientific research. This development trend not only helps improve the efficiency and accuracy of scientific research but also brings more innovation and breakthroughs to the scientific community. The paper was published in the Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(23)64612-1).
###
About the Journal
Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top one journals in Applied Chemistry with a current SCI impact factor of 16.5. The Editors-in-Chief are Profs. Can Li and Tao Zhang.
At Elsevier http://www.journals.elsevier.com/chinese-journal-of-catalysis
Manuscript submission https://mc03.manuscriptcentral.com/cjcatal
JOURNAL
Chinese Journal of Catalysis
ARTICLE TITLE
Large language model in electrocatalysis
