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 gcat–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, NHx 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.