Innovative Approach by MIT: Unified Electrochemical Process for CO2 Capture and Conversion

Researchers have discovered a unified electrochemical method for the simultaneous capture and conversion of carbon dioxide. This method utilizes an electrode, seen in images as covered with bubbles, that attracts carbon dioxide released from a sorbent material and transforms it into carbon-neutral products. Credit: John Freidah/MIT MechE

This breakthrough, rooted in a solitary electrochemical procedure, could significantly reduce emissions from industries that are particularly difficult to decarbonize, including steel and cement production sectors.

In a global push to mitigate greenhouse gas emissions, MIT scientists are honing in on carbon capture technologies tailored to some of the most stubborn industrial polluters.

Certain industries like steel, cement, and chemical manufacturing are especially challenging to decarbonize due to the intrinsic use of carbon and fossil fuels in their processes. If advancements can be made to not only capture but also repurpose carbon emissions within these production cycles, it could result in marked reductions in emissions from these notoriously difficult-to-abate sectors.

Existing experimental technologies for carbon dioxide capture and conversion operate as two distinct, energy-intensive processes. The MIT researchers aim to integrate these processes into a singular, more energy-efficient system that could ideally be powered by renewable energy sources, and thus capture and convert carbon dioxide emissions from concentrated industrial settings.

Recent Insights into Carbon Capture and Conversion

In a paper published on September 5 in the journal ACS Catalysis, the researchers elucidate the complex mechanisms through which carbon dioxide can be simultaneously captured and converted in a single electrochemical process. The technique involves the use of an electrode to attract carbon dioxide, which is released from a sorbent material, and then convert it into a reusable form.

While similar initiatives have been reported, the electrochemical reactions driving these processes have remained elusive. To uncover these mechanisms, the MIT team performed comprehensive experiments and concluded that the efficiency of the electrode is influenced by the partial pressure of the carbon dioxide; the purer the carbon dioxide that contacts the electrode, the more efficient the capture and conversion process.

This discovery about the primary driver or “active species” could guide future adjustments to similar electrochemical systems for efficient, integrated carbon dioxide capture and conversion.

The research suggests that although these systems may not be effective for capturing and converting dilute carbon emissions directly from the atmosphere, they could be very effective for capturing and converting emissions from high-concentration industrial processes, especially those without apparent renewable alternatives.

“Transitioning to renewable energy for electricity is attainable, but thorough decarbonization of sectors like cement and steel is more complex and will take more time,” remarks study author Betar Gallant, the Class of 1922 Career Development Associate Professor at MIT. “Even if we phase out all power plants, interim solutions are needed for emissions from other sectors. Our system fits well in this niche.”

Co-authors of the MIT study include lead author and postdoc Graham Leverick, graduate student Elizabeth Bernhardt, as well as Aisyah Illyani Ismail, Jun Hui Law, Arif Arifutzzaman, and Mohamed Kheireddine Aroua of Sunway University in Malaysia.

Understanding the Carbon Capture Mechanism

Carbon capture technology is generally engineered to trap emissions, known as “flue gas,” emanating from power plants and industrial operations. This usually involves large retrofit installations that channel these emissions into chambers containing a “capture” solution—a blend of ammonia-based compounds that chemically bond with carbon dioxide. This captured form of carbon dioxide can then be segregated and subjected to high temperatures, usually generated by fossil-fuel-powered steam, to be released in its pure form. Subsequently, this gas can be stored in various ways or converted into chemicals or fuels.

“Though carbon capture is a mature technology, it demands substantial installations and is costly and energy-consuming,” notes Gallant. “We seek more modular and versatile technologies, adaptable to diverse carbon dioxide sources. Electrochemical systems could provide this flexibility.”

Gallant’s team is working on an electrochemical system that recovers the captured carbon dioxide and converts it into a usable product. This integrated system could be entirely powered by renewable electricity.

The electrode at the center of their concept interacts with existing carbon-capture solutions. When voltage is applied, electrons flow onto the reactive form of carbon dioxide and convert it into a product using protons from water. This process frees the sorbent to capture more carbon dioxide without the need for steam.

Role of Independent CO2 Molecules

In this new study, the MIT team examined the specific reactions that drive this electrochemical process. Through rigorous testing, they found that the crucial factor was not the type of ammonia-based compound used in the capture solution, but rather the concentration of independent, non-bonded carbon dioxide molecules present. This “solo-CO2” was found to be the primary determinant in the efficiency of converting captured carbon dioxide into carbon monoxide.

“This is not a technology for carbon removal but rather for carbon recycling, enabling us to reuse carbon dioxide while decreasing associated emissions,” states Gallant. “The ultimate goal is to use electrochemical systems to enable mineralization and permanent carbon dioxide storage—a true removal technology. Our current understanding is a stepping stone toward that long-term vision.”

Reference: “Uncovering the Active Species in Amine-Mediated CO2 Reduction to CO on Ag” by Graham Leverick, Elizabeth M. Bernhardt, Aisyah Ilyani Ismail, Jun Hui Law, A. Arifutzzaman, Mohamed Kheireddine Aroua, and Betar M. Gallant*, 5 September 2023, ACS Catalysis.
DOI: 10.1021/acscatal.3c02500

The research is financially supported by Sunway University in Malaysia.

Frequently Asked Questions (FAQs) about Electrochemical Carbon Capture and Conversion

More about Electrochemical Carbon Capture and Conversion

• MIT News Article on Electrochemical Carbon Capture
• ACS Catalysis Journal Publication
• Sunway University Research Support
• Overview of Carbon Capture Technologies
• Challenges in Decarbonizing the Steel and Cement Industries
• Renewable Energy and Carbon Capture: An Integrated Approach