Conversion of CH4 /CO2 by a nanosecond repetitively pulsed discharge

A possible way to store both renewable energy and CO2 in chemical energy is to produce value-added chemicals and fuels starting from CO2 and green electricity. This can be done by exploiting the non-equilibrium properties of gaseous electrical discharges. Discharges, in addition, can be switched on and off quickly, thus being suitable to be coupled with an intermittent energy source. In this study, we have used a nanosecond pulsed discharge to dissociate CO2 and CH4 in a 1:1 mixture at atmospheric pressure, and compared our results with literature data obtained by other discharges. The main products are CO, H2, C2H2, water and solid carbon. We estimate an energy efficiency of 40% for syngas (CO and H2) production, higher if other products are also considered. Such values are among the highest compared to other discharges, and, although not very high on an absolute scale, are likely improvable via possible routes discussed in the paper and by coupling to the discharge a heterogeneous catalysis stage.