Enhanced ammonia production through non-thermal plasma-assisted synthesis: Tailoring titanium oxynitride photocatalysts for optimal performance

A plasma assisted ammonia synthesis over a titanium oxynitride catalyst has been studied in a micro dielectric barrier discharge reactor. The titanium oxynitride were prepared by nitridation of TiO 2 at the temperatures ranging from 650 to 850 °C, allowing control over the nitrogen content and plasmonic properties of the catalyst. Without the catalyst, the highest NH 3 yield of 0.233 vol% and energy efficiency of 0.68 g kWh −1 were observed at the stoichiometric H 2 /N 2 feed ratio of 3.0. However, the optimal H 2 /N 2 feed ratio shifted to 2.0 was observed over the TON-650 catalyst with a further improvement in the NH 3 yield to 0.272 vol% and energy efficiency of 0.79 g kWh −1 . For TON-750, the optical H 2 /N 2 feed ratio further decreased to 1.0, achieving a NH 3 yield of 0.253 vol% and a higher energy efficiency of 0.83 g kWh −1 . These enhancements are attributed to a synergetic effect between plasma and titanium oxynitride surface. A general trend was observed demonstrating that the optimal H 2 /N 2 feed ratio is inversely proportional to the amount of total nitrogen content in the catalysts. This work demonstrates an effective and economically viable method for on-site, on-demand, small-scale ammonia synthesis. • Plasma-assisted N₂-fixation using pyramid micro-discharge with photocatalysts. • TiO₂ and TON used, synthesized via nitriding in NH₃/N₂ atmospheres. • TON properties tuned by N/O ratio via 650–850 °C nitridation. • Achieved 2715 ppm NH₃ at H₂/N₂ = 1:1 vs 2329 ppm at 3:1 (noncatalytic). • Enhanced N₂ activation with minor plasma quenching in N₂-rich mix.