CO$_{2}$ dissociation in vortex-stabilised microwave plasmas

Plasma-assisted gas conversion techniques are widely considered as efficient building blocks in a future energy infrastructure which will be based on intermittent, renewable electricity sources. CO$_{2}$ dissociation in high-frequency plasmas is of particular interest in carbon capture and utilisation process chains for the production of CO$_{2}$-neutral fuels. In order to achieve efficient plasma processes of high throughput specifically designed gas flow and power injection regimes are required. In this contribution vortex-stabilised microwave plasmas in undiluted CO$_{2}$ were studied in a pressure range from 170 to 1000 mbar at up to 1 kW (forward) injected power, respectively. The CO$_{2}$ depletion was measured downstream, e.g. by means of mass spectrometry. Although the system configuration was entirely not optimised, energy efficiencies of nearly 40{\%}, i.e. close to the thermal dissociation limit, and conversion efficiencies of up to 23{\%} were achieved. Additionally, spatially-resolved emission spectroscopy was applied to map the axial and radial distribution of excited atomic (C, O) and molecular (CO, C$_{2})$ species along with their rotational temperatures.