This talk will analyze CO₂ electrolysis from a device perspective to provide insight into what are the bottlenecks in the field and how to resolve them. In particular we will focus on our results using synchrotron based wide angle x-ray scattering to observe CO₂ electrolysis devices in real time while concomitantly measuring anode and cathode product distributions. During higher current density (>100 mA/cm²) CO₂ electrolysis devices are prone to cathodic ‘flooding’ leading to greatly enhanced hydrogen production. We show that during this degradatory issue there is chaotic oscillatory fluctuations in potential, and product distribution. By analyzing these fluctuations in the presence of a synchrotron, we can monitor salt deposition and even electrolyte penetration by a shift in the background scattering signal. From the comprehensive analysis we have developed a hypothesis of why we both see the oscillations as well as flooding. Interestingly, salt solubility and precipitation has a strong role in flooding issues.

We then analyzed various salts (Li, Na, K, Cs) of differing solubility while doing CO₂ electrolysis. The synchrotron analysis demonstrates the importance of salt solubility on stable operation. Switching to CO electrolysis allowed for more soluble hydroxides compared to the carbonates used during CO₂ electrolysis. While this result in more stable hydration management, it did corrode the anode, as evidenced by IrO2 appearing on the cathode. This was resolved by switching to a Ni anode, though long term acetate build-up caused pH issues. The acetate issues was resolved by simply removing the acetate from the anolyte during testing. This allowed for multiple tests with over 100 hour stability.

Asger Moss

Appearances