Plasma-Assisted Ammonia Synthesis from N2 and H2O over rGO-TiO2 Catalysts: Enhancing Energy Efficiency and Unraveling Reaction Mechanisms

The reduction of N₂ to ammonia (NH₃) using H₂O as a hydrogen source is a promising low-carbon alternative to the Haber–Bosch process, but the efficient dissociation of N₂ and H₂O remains a challenge. Here, a reduced graphene oxide–titanium dioxide (rGO-TiO₂) hybrid catalyst was developed to enhance H₂O and N₂ dissociation under dielectric barrier discharge (DBD) plasma, facilitating plasma-assisted ammonia synthesis. The 5-rGO-TiO₂ catalyst achieved an NH₃ formation rate of 4196.62 μmol g_cat^–1 h^–1 and a high energy efficiency of 1317.77 mg kWh^–1. Mechanistic investigations using optical emission spectroscopy (OES), in situ Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) confirmed the formation of reactive nitrogen species, NH_x intermediates, and NH₃, demonstrating the synergistic role of rGO in electron transfer and reactant dissociation. Density functional theory (DFT) calculations further revealed that rGO significantly lowers the energy barriers for N₂ and H₂O dissociation, improving the ammonia synthesis efficiency. Overall, the integration of rGO-TiO₂ with plasma catalysis effectively enhances reactant activation and catalytic performance, offering insights into the design of advanced catalysts for low-energy ammonia production.