Non-thermal plasma synergistic Co–Ni/γ-Al2O3 for ammonia synthesis: performance optimization and mechanism investigation

The development of mild and green ammonia synthesis is a significant and challenging research. In this study, a nanosecond pulse-driven coaxial double dielectric barrier discharge reactor was combined with M/γ-Al 2 O 3 (M = Co, Ni, Co–Ni) catalysts for efficient ammonia synthesis. Key parameters including pulse voltage, gas flow rate, and N 2 /H 2 molar ratio were systematically investigated. The Co–Ni/γ-Al 2 O 3 catalyst achieved the best energy efficiency of 1.11 g/kWh and a synthesis rate of 226.33 μmol g −1  h −1 under optimal conditions, which is 3.44 times higher than that of the plasma only system. Characterization revealed superior metal dispersion, smaller metal particle size, and larger specific surface area for Co–Ni/γ-Al 2 O 3 . Electrical diagnostics and optical emission spectroscopy (OES) showed that catalyst packing enhances discharge intensity and promotes key active species (N 2 ∗, N 2 + , and H α ). Synergistic effects between Co and Ni sites promote ammonia formation. This work provides new insights for designing high-efficiency plasma-catalytic ammonia synthesis systems.