MIT Develops Breakthrough Process to Convert CO2 into Liquid Fuel

New York City: Researchers at the Massachusetts Institute of Technology (MIT), in collaboration with Harvard University, have developed a groundbreaking process for converting carbon dioxide into a usable liquid fuel. This new method efficiently transforms CO2 into formate, a material that can serve as an alternative energy source akin to hydrogen or methanol in electricity generation. The research findings, led by MIT doctoral students Zhen Zhang, Zhichu Ren, Alexander H. Quinn, and Harvard University doctoral student Dawei Xi, under the guidance of MIT Professor Ju Li, were recently detailed in an open-access paper published in Cell Reports Physical Science.

According to World Economic Forum, the conversion process is both efficient and cost-effective, utilizing a catalyst to transform carbon dioxide and water into formate. This substance, which can exist as a liquid or solid, offers a promising solution for long-term storage and energy generation, as it remains stable in ordinary steel tanks for extended periods.

The global quest to effectively capture and utilize carbon dioxide has intensified, particularly as a means to mitigate environmental impacts. Traditional methods for converting CO2 into fuel often result in low carbon efficiency or the production of hard-to-handle, toxic, or flammable fuels. The MIT-Harvard team’s method overcomes these hurdles by producing formate, a non-toxic, non-flammable substance that is easy to store and transport.

This innovative process first involves converting CO2 into an intermediate form, liquid metal bicarbonate. This is then electrochemically transformed into liquid potassium or sodium formate in an electrolyzer powered by low-carbon electricity sources like nuclear, wind, or solar power. The resultant highly concentrated formate solution can be dried to produce a solid powder, remarkably stable and suitable for long-term storage.

Several optimization steps by the research team have transformed this chemical conversion process into a practical solution. The carbon capture and conversion process begins with an alkaline solution-based capture, concentrating CO2 into liquid metal-bicarbonate solution. This is subsequently electrochemically converted into solid formate crystals with a carbon efficiency exceeding 96 percent. The stability of these crystals is such that they can be stored for years, or even decades, without significant loss.

This breakthrough contrasts with existing hydrogen storage methods, which allow for a 1 percent per day gas leak, and methanol, a toxic substance not suitable for leak-prone environments. Formate, in comparison, is widely used and recognized as safe according to national safety standards.

Key to the success of this process is the balance of pH levels, ensuring steady-state conversion without efficiency loss over time. The system, tested for over 200 hours, showed no significant decrease in output. The researchers also overcame challenges related to unwanted side reactions and designed a fuel cell optimized for formate fuel to produce electricity.

The potential applications of this technology range from household units to industrial and grid-scale storage systems. For initial household applications, an electrolyzer unit about the size of a refrigerator could capture and convert CO2 into formate, stored in a tank and later used to power a fuel cell for electricity and heat.

Ted Sargent, a professor at Northwestern University not involved in this work, highlights the potential of a “formate economy,” noting the benign and stable nature of metal formate salts as compelling energy carriers. The project received support from the U.S. Department of Energy Office of Science.