Energy Efficiency in Non-Thermal Plasma and Plasma-Catalytic Processes: Principles, Challenges, and Design Strategies

The increasing availability of variable renewable electricity has stimulated interest in plasma-assisted technologies for electrified chemical conversion. Non-thermal plasmas enable molecular activation over wide operating windows, while certain configurations offer flexible operation and rapid electrical response, making them potentially compatible with intermittent renewable power. However, energy efficiency remains a major barrier to practical deployment, particularly for dielectric barrier discharge (DBD) and plasma-catalytic systems. For CO2 splitting, representative DBD systems typically exhibit energy efficiencies below ~10%, with selected cases approaching ~20%, whereas microwave and gliding arc plasmas can reach ~40–80% under specific conditions, although auxiliary energy demands are not always included. This review provides an energy-centric assessment of plasma-assisted processes, with particular emphasis on plasma-catalytic gas conversion. Energy-performance metrics are critically examined, followed by analysis of how operating conditions, reactor design, and catalyst properties govern energy deposition, reactive-species generation and transport, and plasma–surface interactions. Drawing on plasma-only and plasma-catalytic studies, transferable principles are identified for improving energy utilization. The analysis highlights that energy-efficient plasma processing requires coordinated control of energy deposition, species lifetimes and transport, reactor configuration, and surface reaction pathways, providing design guidelines toward scalable renewable-electricity-driven chemical manufacturing.