*Communication* **Towards High Efficiency CO2 Utilization by Glow Discharge Plasma**

**Stephan Renninger \*, Paul Rößner, Jan Stein, Maike Lambarth and Kai Peter Birke**

Electrical Energy Storage Systems, Institute for Photovoltaics, University of Stuttgart, Pfaffenwaldring 47, 70569 Stuttgart, Germany; paul.roessner@ipv.uni-stuttgart.de (P.R.); jan.stein@ipv.uni-stuttgart.de (J.S.); maike.lambarth@ipv.uni-stuttgart.de (M.L.); peter.birke@ipv.uni-stuttgart.de (K.P.B.)

**\*** Correspondence: stephan.renninger@ipv.uni-stuttgart.de; Tel.: +49-711-6856-1508

**Abstract:** Plasma technology reaches rapidly increasing efficiency in catalytic applications. One such application is the splitting reaction of CO2 to oxygen and carbon monoxide. This reaction could be a cornerstone of power-to-X processes that utilize electricity to produce value-added compounds such as chemicals and fuels. However, it poses problems in practice due to its highly endothermal nature and challenging selectivity. In this communication a glow discharge plasma reactor is presented that achieves high energy efficiency in the CO2 splitting reaction. To achieve this, a magnetic field is used to increase the discharge volume. Combined with laminar gas flow, this leads to even energy distribution in the working gas. Thus, the reactor achieves very high energy efficiency of up to 45% while also reaching high CO2 conversion efficiency. These results are briefly explained and then compared to other plasma technologies. Lastly, cutting edge energy efficiencies of competing technologies such as CO2 electrolysis are discussed in comparison.

**Keywords:** plasma catalysis; CO2 splitting; glow discharge; energy efficiency; CO2 electrolysis; CO2 utilization; magnetic field; power-to-X
