Synergistic effects of light and plasma catalysis on Au-modified TiO<sub>2</sub> nanotube arrays for enhanced non-oxidative coupling of methane.

Abstract

The direct conversion of methane into value-added hydrocarbons represents one of the most energetically efficient pathways to shift industrial processes towards more sustainable low-carbon technologies. In this study, we present a novel planar dielectric barrier discharge (DBD) reactor equipped with a quartz window for catalyst illumination, to explore potential synergies between light and plasma in the catalytic non-oxidative coupling of methane (NOCM) reaction. Highly ordered TiO₂ nanotube arrays were grown on a Ti mesh and further modified with Au nanoparticles to improve light absorption and reactivity, thereby acting as the DBD electrode and NOCM catalyst. The introduction of gold significantly enhances performances, achieving a substantial rise of 64% in plasma-assisted methane conversion compared to the bare support while shifting the selectivity towards alkanes and C₃₊ hydrocarbons. For the first time, we demonstrated the effect of light irradiation and its interaction with plasma, revealing an effective synergistic mechanism between plasma and light in gold-modified materials. Notably, a 21.5% increase in the intrinsic rate of the NOCM surface process under irradiation was achieved. This improvement is attributed to two factors: induced physical changes in the nature of the plasma micro-discharges and the creation of specific surface vibrational states on the catalyst.