Efficient synthesis of ammonia from N₂ and H₂ alone in a ferroelectric packed-bed DBD reactor

A detailed study of ammonia synthesis from hydrogen and nitrogen in a planar dielectric barrier discharge (DBD) reactor was carried out. Electrical parameters were systematically varied, including applied voltage and frequency, electrode gap, and type of ferroelectric material (BaTiO₃ versus PZT). For selected operating conditions, power consumption and plasma electron density were estimated from Lissajous diagrams and by application of the Bolsig  +  model, respectively. Optical emission spectroscopy was used to follow the evolution of plasma species ($\text{N}{\text{H}}^{\ast },{\text{N}}^{\ast },N_2^{+}\text{and}{N}_2^{\ast }$) as a function of applied voltage with both types of ferroelectric material. PZT gave both greater energy efficiency and higher ammonia yield than BaTiO₃: 0.9 g NH₃ kWh⁻¹ and 2.7% single pass N₂ conversion, respectively. This performance is substantially superior to previously published findings on DBD synthesis of NH₃ from N₂ and H₂ alone. The influence of electrical working parameters, the beneficial effect of PZT and the importance of controlling reactant residence time are rationalized in a reaction model that takes account of the principal process variables (paper)