Probing the role of a non-thermal plasma (NTP) in the hybrid NTP catalytic oxidation of methane

Three recurring hypotheses are often used to explain the effect of non-thermal plasmas (NTPs) on NTP catalytic hybrid reactions; namely, modification or heating of the catalyst or creation of new reaction pathways by plasma-produced species. NTP-assisted methane (CH4) oxidation over Pd/Al2O3 was investigated by direct monitoring of the X-ray absorption fine structure of the catalyst, coupled with end-of-pipe mass spectrometry. This in situ study revealed that the catalyst did not undergo any significant structural changes under NTP conditions. However, the NTP did lead to an increase in the temperature of the Pd nanoparticles; although this temperature rise was insufficient to activate the thermal CH4 oxidation reaction. The contribution of a lower activation barrier alternative reaction pathway involving the formation of CH3(g) from electron impact reactions is proposed