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Reducing CO2 to formic acid

| By Gerald Ondrey

A research team led by Kenneth C. Neyerlin at the National Renewable Energy Laboratory (NREL; Golden, Colo.; www.nrel.gov), with members from Argonne National Laboratory (Lemont, Ill; www.anl.gov) and Oak Ridge National Laboratory (Tenn.; www.ornl.gov) has developed a membrane electrode assembly (MEA) for the efficient electrochemical reduction of CO2 into formic acid.

The MEA in an electrolyzer cell typically includes an ionically conductive membrane (cation or anion exchange) pressed between two electrodes consisting of electrocatalysts and ionically conducting polymers. Leveraging the team’s experience in fuel cells and water electrolysis technology, they investigated several MEA configurations in an electrolyzer cell to compare electrochemical reduction of CO2 to formic acid.

As described in a recent issue of Nature Communications, the key technological advancement is a perforated cation-exchange membrane (diagram), which, when utilized in a forward-bias, bipolar-membrane configuration, allows formic acid generated at the membrane interface to exit through the anode flow field. This perforated membrane helped achieve stable, high-selectivity formic acid production, and it simplifies the design by using off-the-shelf components, according to the authors.

“The result of this study is a paradigm shift in the electrochemical production of organic acids like formic acid,” Neyerlin says. “The perforated membrane architecture reduces the complexity of previous designs and can also be leveraged to improve energy efficiency and durability for other electrochemical CO2-conversion devices.”

Formic acid is a potential intermediate chemical with a wide range of applications, especially as a raw material for the chemical or biomanufacturing industries. Formic acid has also been identified as an input for biological upgrading into sustainable aviation fuel (SAF).