New Electrochemical Cell Converts Captured Carbon into Formate

Researchers at Tokyo Metropolitan University have made significant progress in developing an industrial process to convert bicarbonate solution, derived from captured carbon, into formate solution, a sustainable green fuel. The journal EES Catalysis published the study.

The novel electrochemical cell, which has a porous membrane layer positioned between the electrodes, solves significant problems with reactive carbon capture (RCC) and produces results that are on par with energy-intensive gas-fed processes. Such processes are essential to achieving net zero emissions because they directly enhance the value of waste streams.

A significant component of the global plan to combat climate change and cut emissions is carbon capture technology. However, the crucial question of what to do with the carbon dioxide that has been caught is still unanswered. Should people just shove it under the rug or is there more to it? Scientists are certain of this.

An effort is underway to transform the captured product into something more beneficial for society by using cutting-edge catalysts and chemical processes.

The process of turning carbon dioxide into an eco-friendly fuel is especially useful. Technology has been created to convert carbon dioxide into a formate molecule, which may then be used in formate fuel cells to produce electricity. This process involves the use of electrochemical cells. The requirement for pure carbon dioxide, however, presents a major challenge because pressurizing carbon dioxide can be quite energy-intensive.

The cells do not survive very long, and the gas conversion is not particularly efficient. Reactive carbon capture allows formate ions to be produced directly from carbon dioxide dissolved in alkaline solutions, such as bicarbonate solutions, without the losses involved in supplying pure gas.

The main task at hand for the researchers is to improve the electrochemical cell so that formate ions may be produced from bicarbonate ions selectively without being lost to unintended reactions like the creation of hydrogen.

Recently, a group of scientists under the direction of Tokyo Metropolitan University professor Fumiaki Amano developed a novel cell that has exceptional selectivity for the transformation of bicarbonate ions into formate ions. In the novel cell, a porous cellulose ester membrane divides a polymer electrolyte membrane from catalytic material electrodes.

The electrolyte membrane allows hydrogen ions generated at one electrode to enter the porous layer, where they combine with bicarbonate ions to form carbon dioxide within the pores effectively. At the opposite electrode, which is likewise in touch with the porous membrane, the gas is subsequently transformed into formate ions.

When they tested their cell, they discovered that even at extremely high currents, its faradaic efficiency, the percentage of electrons converted to formate rather than other compounds was 85%. This not only works better than previous designs, but it also operates smoothly for more than 30 hours, achieving almost full conversion of bicarbonate to formate. All that was left when the water was removed was crystalline, solid formate fuel.

This kind of enhancement in the efficient operation of electrochemical cells promises to have a significant influence, especially considering the pressures on climate change technologies. As society works to become more environmentally friendly, the team expects that its novel bicarbonate electrolyzer will be a practical solution.

This study was funded by the Tokyo Metropolitan Government.

Journal Reference:

Nomoto, K., et al. (2024) Highly selective formate formation via bicarbonate conversions. EES Catalysis. doi.org/10.1039/d4ey00122b.