High temperature solid-oxide electrolysis cells (SOECs) are a promising conversion technology to produce energy-rich molecules such as CO from CO2. The high energy efficiency and separation of product streams intrinsic to oxygen ion-conducting electrolyte materials are desirable for renewable synthetic fuel and value-added chemical production at industrial scale. While the SOEC performance has been improved by advancements in electrode materials and cell design in recent years, the use of plasmas to enhance SOEC performance also shows great potential. Previous studies show that the oxygen exchange rate for yttria-stabilized zirconia (YSZ) can increase by two orders of magnitude simply by exposure to plasma. However, the underlying mechanisms of plasma and surface processes are presently not well understood. A common explanation is that plasma-activated species (e.g., by vibrational excitation, plasma-dissociation and ionization) support the reduction kinetics on the surface. The effects of plasma-induced surface charging and local fields on, for instance, the vacancy concentration and exchange kinetics may also play a significant role. Dedicated experiments aimed to distinguish between these underlying mechanisms are essential to reveal the true nature of the synergy. In this contribution, we will present our novel hybrid plasma-SOEC reactor dedicated to investigating the fundamental aspects of SOEC-plasma synergy. The quiescent region of an inverse brush cathode glow discharge is used for experiments, providing a highly stable, homogeneous and field-free plasma environment well suited for a controlled exposure of the SOEC. Langmuir probe measurements will give insights into the plasma properties and provide reference for plasma-kinetic modelling of the plasma bulk and wall region. With this, we intend not only to quantify the plasma-effect on SOEC performance, but also to develop insights into the rate-limiting kinetics. We will share our first experimental results on plasma-enhanced oxygen pumping in an O2/He plasma environment.

Experimental investigations into the synergy of plasma-enhanced high-temperature solid-oxide electrolysis

ACS Spring Meeting 2021

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