A major development in carbon capture and utilization technology has been achieved by researchers at Tokyo Metropolitan University (TMU). They have developed a new type of electrochemical cell that can effectively convert a product derived from captured carbon into a potent source of green fuel. This innovative technique overcomes major challenges in reactive carbon capture (RCC) and demonstrates performance levels similar to those of the more energy-intensive traditional gas-fed methods.
“Carbon capture and utilization to convert atmospheric CO2 into useful chemicals and fuels is essential for achieving a carbon-neutral or negative emission future,” said the researchers. “But the important question of what we do with the captured carbon dioxide remains an open challenge. Do we simply push it underground, or is there more to it?”
One promising approach to making use of captured carbon dioxide involves using electrochemical cells to convert carbon dioxide into formate, a substance that can generate power in fuel cells. Unfortunately, this approach has also faces some challenges, as it requires pure carbon dioxide which is created through pressurizing – a highly energy intensive process.
The team at TMU looked at reactive carbon capture as an alternative solution to the problem, as it would eliminate the need for pure CO2 and simplifies the conversion process.
“Enter reactive carbon capture, where carbon dioxide dissolved in alkaline solutions, like bicarbonate solutions, can be directly used to create formate ions without the losses associated with providing pure gas,” the team stated.
In order to design an electrochemical cell that can selectively produce formate ions from bicarbonate – while also minimizing unwanted reactions – they created an innovative cell that overcomes the primary issues in reactive carbon capture.
“In the new cell, electrodes made of catalytic material are separated from a polymer electrolyte membrane by a porous membrane made of cellulose ester,” they said.
This innovation allows hydrogen ions generated at one electrode to move through the electrolyte membrane to the porous layer, where they react with bicarbonate ions to produce carbon dioxide within the pores.
“The gas is then converted to formate ions at the other electrode, also in contact with the porous membrane.”
The team states that the new cell achieved an 85% faradaic efficiency at high currents, meaning that 85% of the electrons are transformed into formate, outperforming existing designs. The cell remained stable for over 30 hours, achieving a nearly complete conversion of bicarbonate to formate. After removing water, the end product is a solid, crystalline formate fuel ready for use.
“The team hopes their new bicarbonate electrolyzer can be a viable option for society as it strives towards a green transformation,” they stated.