Computationally guided dopant discovery for boosting TiO2 catalysts in plasma-assisted non-oxidative coupling of methane

초록

The direct conversion of methane into value-added C2 hydrocarbons offers a promising route to mitigate climate change and reduce reliance on fossil-derived feedstocks. Plasma-assisted methane coupling enables C–H bond activation under mild, oxidant-free conditions, but plasma-only systems suffer from poor selectivity and significant carbon deposition. To overcome these challenges, heterogeneous catalysts have been explored to steer reaction pathways and suppress coke formation. Titanium dioxide (TiO2), known for its coke resistance, shows promise under plasma condition but remains limited by low activity and selectivity. Here, we present a combined theoretical and experimental study to enhance the catalytic performance of TiO2 for non-oxidative plasma-assisted methane coupling (NOCM). Density functional theory (DFT) calculations were performed to assess the effect of 3d transition metal doping (V, Cr, Mn, Fe, Co, Ni, Cu) on methane activation and C2 product formation, followed by microkinetic modeling under plasma-relevant conditions. Vanadium emerged as the most effective dopant for enhancing CH4 activation and C2H6 production. Based on these findings, V-doped TiO2 catalysts were synthesized and tested in a DBD plasma reactor, showing improved CH4 conversion and C2H6 yield compared to pristine TiO2. Additionally, the yields of heavier C3–C9 hydrocarbons increased, and coke formation was significantly suppressed. Overall, this study highlights a rational catalyst design strategy that maintains TiO2’s coke resistance while enhancing activity and selectivity for sustainable methane valorization under plasma condition.

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