Improving Plasma‐Catalytic Ammonia Synthesis Using a Coaxial Double‐Helix‐Electrode Reactor

Developing energy‐efficient ammonia synthesis under mild and carbon‐neutral conditions remains a major challenge for sustainable nitrogen fixation. Here, we present a coaxial double‐helix‐electrode‐based double‐dielectric barrier discharge (DBD) reactor, termed a “double‐helix” design, featuring dual quartz barriers and symmetric high‐voltage and grounded electrodes to achieve uniform, high‐intensity volume discharge for plasma‐catalytic ammonia synthesis. Three‐dimensional electrostatic simulations demonstrate that this configuration generates a strongly coupled and spatially homogeneous electric field (∼7 × 10 6 V m −1 ), significantly outperforming conventional single‐dielectric DBD designs (∼1 × 10 6 V m −1 ). An optimized Ni electrode with a 1 mm winding pitch increases electron density, as evidenced by optical emission spectroscopy (OES, I N2+ (425 nm)/ I N2* (335 nm) = 0.15). Under plasma‐only operation, the double‐helix DBD reactor produces approximately 2.5‐fold higher NH 3 concentration than a conventional DBD at identical power input. When integrated with a Ni/Al 2 O 3 catalyst, synergistic plasma‐catalyst interactions further enhance ammonia yield and energy efficiency, achieving an energy yield of up to 3.68 g NH 3 kWh −1 under 5.92 W discharge. Comprehensive analysis combining electric‐field simulations, transient discharge imaging, and catalytic performance measurements elucidates the intrinsic coupling between electrode architecture, discharge physics, and catalytic function. This work demonstrates that electric‐field engineering is an effective strategy for enabling stable volume discharge and enhancing plasma‐catalytic ammonia synthesis, offering a generic design principle for next‐generation low‐carbon nitrogen‐fixation systems.