(280c) Direct Air Capture of Carbon Dioxide Using Nickel Hydroxide Batteries in a Membrane Electrode Assembly

Direct air capture (DAC) is a growing field responding to the need to remove carbon dioxide from the atmosphere. Several technologies are being developed today attempting to meet this need. The technology furthest in development are temperature swing adsorption technologies which have recently moved out of the pilot plant scale.¹ This presentation looks to present an electrochemical device as alternative to these technologies.

The electrochemical device proposed is a pair of nickel hydroxide (Ni(OH)₂) battery electrodes which produce hydroxide (OH^-). The hydroxide reacts with carbon dioxide (CO₂) to create carbonate (CO₃^2-) and bicarbonate (HCO₃^-). These carbonates can be transported from the cathode across an anion exchange membrane to the anode where they are evolved back into CO₂ due to a pH reduction at the anode. This builds on work that optimized a Hydroxide Exchange Membrane Fuel Cell (HEMFC) for CO₂ capture, showing the efficacy of an electrochemically mediated pH swing carbon capture device.^2,3

The benefit of the nickel hydroxide battery approach is the low energy cost associated with separation. Because a pair of nickel hydroxide batteries undergo the same electrochemical reaction, low potentials, and thus low energy cost is required. Experiments have shown device level energy requirements of less than 1 MWh ton^-1CO₂. Most of the energy required by the device produces the pH gradient used to capture and release CO₂.

The biggest hurdle for this electrochemical approach is increasing the flux of CO₂ to allow for more compact devices. Strategies for managing the transient charge and discharge behavior of the battery system will be discussed. Focus will be on improving flux to reduce the overall cost of the device.

References

1 Gambhir, A. & Tavoni, M. Direct Air Carbon Capture and Sequestration: How It Works and How It Could Contribute to Climate-Change Mitigation. One Earth 1, 405-409 (2019). https://doi.org:10.1016/j.oneear.2019.11.006

2 Matz, S., Setzler, B. P., Weiss, C. M., Shi, L., Gottesfeld, S. & Yan, Y. Demonstration of Electrochemically-Driven CO2 Separation Using Hydroxide Exchange Membranes. Journal of The Electrochemical Society 168 (2021). https://doi.org:10.1149/1945-7111/abd5fe

3 Shi, L., Zhao, Y., Matz, S., Gottesfeld, S., Setzler, B. P. & Yan, Y. A shorted membrane electrochemical cell powered by hydrogen to remove CO2 from the air feed of hydroxide exchange membrane fuel cells. Nature Energy 7, 238-247 (2022). https://doi.org:10.1038/s41560-021-00969-5