Editors' Choice—Power-Generating Electrochemical CO2 Scrubbing from Air Enabling Practical AEMFC Application

Anion exchange membrane fuel cells (AEMFCs) have been widely touted as a low-cost alternative to existing proton exchange membrane fuel cells. However, AEMFCs operating on air suffer from a severe performance penalty caused by carbonation from exposure to CO₂. Many approaches to removing CO₂ from the cathode inlet would consume valuable energy and complicate the systems-level balance-of-plant. Therefore, this work focuses on an electrochemical solution where CO₂ removal would still generate power, but not expose an entire AEMFC stack to carbonation conditions. Such a system consists of two AEMFCs in series. The first AEMFC, which acts as an anion exchange CO₂ separator (AECS), is relatively small and serves to scrub CO₂ from the air. The AECS is powered by the hydrogen bleed from the second (i.e., main) AEMFC. A small amount of hydrogen is bled from the recycled hydrogen used in the main AEMFC to mitigate impurity build-up, including nitrogen gas from diffusion across its membrane. The second, main AEMFC operates on the purified air output from the AECS and fresh H₂. This work shows that it is possible to use an AECS to lower the CO₂ concentration in the AEMFC input air stream to values low enough that the main AEMFC can be operated stably for extended periods, 150 h in this demonstration. Also, in this study, AEMFCs are operated on AECS-purified air without experiencing a performance penalty. Lastly, the relative geometric active area of the AEMFC and AECS devices are evaluated and discussed.

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