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

The reduction of N 2 to ammonia (NH 3 ) using H 2 O as a hydrogen source is a promising low-carbon alternative to the Haber–Bosch process, but the efficient dissociation of N 2 and H 2 O remains a challenge. Here, a reduced graphene oxide–titanium dioxide (rGO-TiO 2 ) hybrid catalyst was developed to enhance H 2 O and N 2 dissociation under dielectric barrier discharge (DBD) plasma, facilitating plasma-assisted ammonia synthesis. The 5-rGO-TiO 2 catalyst achieved an NH 3 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 NH 3, 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 N 2 and H 2 O dissociation, improving the ammonia synthesis efficiency. Overall, the integration of rGO-TiO 2 with plasma catalysis effectively enhances reactant activation and catalytic performance, offering insights into the design of advanced catalysts for low-energy ammonia production.