Making shows 3 parts as if on a grey table: a white model house on top; a fuel cell sandwiched in between two metal plates with spherical particles drifting around it; and on bottom is the electrolyzer, which looks similar to the fuel cell and has particles floating around it. Credit: Shuhan Miao, Harvard Graduate School of Design
The new procedure, developed by MIT doctoral trainees Zhen Zhang, Zhichu Ren, and Alexander H. Quinn; Harvard University doctoral student Dawei Xi; and MIT Professor Ju Li, is described this just recently in an open-access paper in Cell Reports Physical Science. The entire procedure– including capture and electrochemical conversion of the gas to a solid formate powder, which is then utilized in a fuel cell to produce electrical power– was demonstrated at a little, laboratory scale. However, the scientists expect it to be scalable so that it could offer emissions-free heat and power to specific homes and even be used in commercial or grid-scale applications.
Improved Efficiency and Practicality
Other approaches to converting co2 into fuel, Li describes, normally involve a two-stage procedure: First the gas is chemically caught and turned into a strong type as calcium carbonate, then later that material is warmed to repel the carbon dioxide and convert it to a fuel feedstock such as carbon monoxide gas. That second action has really low performance, usually converting less than 20 percent of the gaseous carbon dioxide into the preferred item, Li says.
By contrast, the new process achieves a conversion of well over 90 percent and gets rid of the need for the ineffective heating step by first transforming the carbon dioxide into an intermediate kind, liquid metal bicarbonate. That liquid is then electrochemically converted into liquid potassium or salt formate in an electrolyzer that uses low-carbon electrical power, e.g. nuclear, wind, or solar power. The extremely concentrated liquid potassium or salt formate option produced can then be dried, for example by solar evaporation, to produce a strong powder that is highly stable and can be kept in ordinary steel tanks for as much as years or perhaps years, Li says.
An electrolzyer setup with a bicarbonate cathode, intermediate buffer layer, cation exchange membrane and a water anode. Credit: Shuhan Miao, Harvard Graduate School of Design
Several steps of optimization established by the group made all the difference in altering an inefficient chemical-conversion procedure into a useful option, states Li, who holds joint appointments in the departments of Nuclear Science and Engineering and of Materials Science and Engineering.
Conversion Process and Applications
The process of carbon capture and conversion involves first an alkaline solution-based capture that focuses co2, either from focused streams such as from power plant emissions or from really low-concentration sources, even outdoors, into the type of a liquid metal-bicarbonate service. Through the use of a cation-exchange membrane electrolyzer, this bicarbonate is electrochemically transformed into strong formate crystals with a carbon performance of higher than 96 percent, as validated in the groups lab-scale experiments.
Methanol, another commonly checked out alternative for transforming carbon dioxide into a fuel usable in fuel cells, is a toxic substance that can not quickly be adjusted to utilize in circumstances where leakage could pose a health threat. Formate, on the other hand, is widely used and thought about benign, according to national safety standards.
Technical Improvements
A number of enhancements account for the significantly improved efficiency of this process. Initially, a careful style of the membrane materials and their setup gets rid of an issue that previous efforts at such a system have actually come across, where an accumulation of particular chemical byproducts changes the pH, triggering the system to progressively lose performance over time. “Traditionally, it is tough to accomplish long-lasting, stable, constant conversion of the feedstocks,” Zhang states. “The secret to our system is to achieve a pH balance for steady-state conversion.”
To achieve that, the scientists carried out thermodynamic modeling to develop the brand-new process so that it is chemically balanced and the pH remains at a consistent state without any shift in acidity in time. It can therefore continue operating effectively over long durations. In their tests, the system ran for over 200 hours with no substantial reduction in output. The entire process can be done at ambient temperature levels and fairly low pressures (about 5 times air pressure).
Another problem was that unwanted side reactions produced other chemical items that were not beneficial, however the team found out a way to avoid these side reactions by the introduction of an additional “buffer” layer of bicarbonate-enriched fiberglass wool that blocked these reactions.
The group likewise built a fuel cell specifically optimized for using this formate fuel to produce electrical power. The kept formate particles are simply dissolved in water and pumped into the fuel cell as required. The solid fuel is much heavier than pure hydrogen, when the weight and volume of the high-pressure gas tanks required to store hydrogen is thought about, the end result is an electrical energy output near parity for a given storage volume, Li states.
Potential Applications
The formate fuel can potentially be adjusted for anything from home-sized systems to large scale commercial uses or grid-scale storage systems, the researchers say. Preliminary home applications might involve an electrolyzer unit about the size of a refrigerator to record and transform the carbon dioxide into formate, which might be saved in an underground or rooftop tank. When needed, the powdered solid would be blended with water and fed into a fuel cell to offer power and heat. “This is for community or family presentations,” Zhang states, “however we think that likewise in the future it might benefit factories or the grid.”
” The formate economy is an interesting concept due to the fact that metal formate salts are really benign and steady, and an engaging energy carrier,” says Ted Sargent, a teacher of chemistry and of electrical and computer engineering at Northwestern University, who was not connected with this work. “The authors have actually shown improved efficiency in liquid-to-liquid conversion from bicarbonate feedstock to formate, and have shown these fuels can be used later on to produce electricity,” he says.
Reference: “A carbon-efficient bicarbonate electrolyzer” by Zhen Zhang, Dawei Xi, Zhichu Ren and Ju Li, 30 October 2023, Cell Reports Physical Science.DOI: 10.1016/ j.xcrp.2023.101662.
The work was supported by the U.S. Department of Energy Office of Science.
By David L. Chandler, Massachusetts Institute of Technology
November 9, 2023
An advancement by MIT and Harvard researchers permits effective conversion of co2 into stable, safe formate, possibly replacing fossil fuels and appropriate for long-lasting storage and electrical energy generation.
The method directly transforms the greenhouse gas into formate, a solid fuel that can be saved forever and might be used to heat homes or power industries.
The search is on worldwide to find methods to draw out co2 from the air or from power plant exhaust and then make it into something useful. One of the more promising concepts is to make it into a steady fuel that can change fossil fuels in some applications. The majority of such conversion processes have actually had problems with low carbon efficiency, or they produce fuels that can be tough to deal with, poisonous, or flammable.
Breakthrough in CO2 to Fuel Conversion
Now, researchers at MIT and Harvard University have established an efficient procedure that can convert carbon dioxide into formate, a liquid or solid product that can be used like hydrogen or methanol to power a fuel cell and produce electrical energy. Potassium or sodium formate, currently produced at commercial scales and typically utilized as a de-icer for roadways and pathways, is nontoxic, nonflammable, simple to store and transportation, and can remain steady in ordinary steel tanks to be used months, and even years, after its production.
One of the more appealing concepts is to make it into a stable fuel that can change fossil fuels in some applications. The whole procedure– consisting of capture and electrochemical conversion of the gas to a strong formate powder, which is then utilized in a fuel cell to produce electrical power– was demonstrated at a small, lab scale. Methanol, another extensively checked out option for converting carbon dioxide into a fuel usable in fuel cells, is a harmful substance that can not easily be adapted to use in circumstances where leakage could present a health danger. The team also constructed a fuel cell particularly enhanced for the usage of this formate fuel to produce electrical energy. The formate fuel can possibly be adapted for anything from home-sized units to big scale commercial usages or grid-scale storage systems, the scientists state.
