Plasma-electrochemical cell interaction: a novel approach to study plasma-surface chemical interactions

In recent work we have proposed the combination of a plasma source and an electrochemical cell, a so-called hybrid plasma-solid oxide electrolysis cell (SOEC) system, to overcome various drawbacks of direct plasma catalysis approaches. One of the advantages is the separation of reagents interacting with the electrocatalyst under plasma afterglow conditions, so that fundamental reactions of reactive species, created in the plasma, can be investigated in detail. The hybrid configuration has shown promise in NO_x and NH₃ formation and CO₂ splitting processes with oxygen separation [1-5].

In this work the solid oxide electrolysis cell is operated under open circuit conditions and is floating with respect to the plasma afterglow. This means no mass oxygen transport is occurring through the electrochemical cell. Without plasma, the electrochemical cell, which conducts only O^2-, will develop a so-called Nernst potential or open circuit potential (OCP), which depends only on the temperature of the cell (typ. >600 ^oC) and the difference of the partial oxygen pressures across the cell. With plasma present, reactive species, such as atomic oxygen and nitrogen, vibrationally and electronically excited molecules, change the oxygen surface coverage of the cell-electrode exposed to the plasma afterglow. This will lead to a change of the OCP. We will present time dependent studies of the reactions occurring on the electrode surface of a symmetric Pt|YSZ|Pt and LSM|YSZ|LSM electrochemical cell, when exposed to oxygen and nitrogen containing plasmas. By varying the temperature we can determine the activation energy of these reactions. Moreover, the in depth studies reveal that these electrochemical cells provide a potential way to determine the atomic oxygen flux in oxygen containing plasmas.

1. H. Patel et al., ACS Energy Lett. 4, 2091 (2019)

2. R.K. Sharma et al., ACS Energy Lett. 6, 313 (2021)

3. The Plasma-Solid Oxide Interface, PhD thesis Xingyu Chen, Eindhoven University of Technology (2025)

4. S. Mori et al, Plasma Process. Polym. 14, 1600153 (2017).

5.G. Chen et al., Chem. Eng. J. 392, 123699 (2020).