Catalyst-free single-step reforming of CO2 and C2H6 into high-value C2+ oxygenates via two-stage tandem nanosecond pulsed plasma

Plasma-assisted CO 2 conversion enables mild carbon resource utilization, yet selective C C coupling for direct C 2+ oxygenate synthesis from CO 2 and light alkanes remains challenging. In this work, we developed a catalyst-free single-step plasma activation strategy that enabled the direct conversion of CO 2 and C 2 H 6 into C 2+ oxygenated chemicals under ambient conditions. Rational optimization of pulsed plasma parameters within a home-made dual-stage tandem reactor revealed pulse repetition frequency as the dominant parameter of co-conversion behavior. Increasing the pulse repetition frequency markedly enhanced reactant activation, with the maximum CO 2 and C 2 H 6 conversions reaching 56.0% and 94.2%, respectively, at 10 kHz. Under this high-conversion condition, a C 2+ oxygenate selectivity of 57.0% was retained, corresponding to a total energy efficiency of 197.5 mmol/kWh. In comparison, the peak energy efficiency (380.6 mmol/kWh) and the maximum C 2+ oxygenate selectivity (58.4%) were achieved at 2 kHz and 6 kHz, respectively, revealing a fundamental trade-off between energy input and integration of CO 2 -derived oxygen species with C 2 H 6 -derived carbon radicals. In-situ DRIFT and product analysis identify ethoxy intermediates as key precursors for oxygenate formation, where hydrogenation, oxidation and radical coupling govern selective oxygenate generation. These findings provide mechanistic insights of plasma-assisted CO 2 /light alkane co-conversion for sustainable production of value-added chemicals.