The Impact of Polarization on Surface Electric Field Amplification and Plasma Intensification in Non-Thermal Plasma-catalysis

Abstract

Non-thermal Plasma (NTP) is a promising method for the chemical transformation of hard-to-activate molecules (e.g., CO2 and CH4). However, plasma chemistry produces a cocktail of highly reactive species and often lacks selectivity toward desired products. Plasma-catalysis is an emerging subfield of heterogeneous catalysis that can narrow plasma chemistry to specific reaction pathways. Nevertheless, most catalysts used in plasma catalysis are based on thermal reactions, where heat drives the reaction. In contrast, the electric field drives plasma-related reactions. Therefore, this project aims to develop catalysts compatible with a plasma environment and responsive to electric-field-driven processes. Accordingly, we investigated the synergism of the inherent ferroelectricity of the catalyst as a mechanism to couple the solid-state material properties directly with the plasma’s electric field. Sodium niobate (NaNbO3) and potassium niobate (KNbO3), known for their ferroelectricity, were synthesized via solvothermal and modified Pechini methods. We investigated their catalytic effects both in pure and composite forms. The morphology and crystalline structure of the catalysts were characterized through SEM, XRD, and FTIR. Moreover, we investigated the impact of these structures on plasma intensity through optical emission spectroscopy (OES). The synthesized catalysts were then tested for CO2 and CH4 decomposition via dry reforming of methane (DRM). The results suggested that the spontaneous and switchable polarization inherent in ferroelectric materials locally amplifies the surface electric field, which in turn intensifies the plasma by ionizing the surrounding gas. The ions accelerate in the applied field, so their path to the catalyst surface is shorter than the diffusion length and relaxation time, thereby boosting their contribution to surface reactions.