Plasma activation of methane for hydrogen in microwave liquid discharge by auxiliary gases: a way to realize efficient utilization of resources

Given the excited state species generated by the discharge gas can activate CH4 in gas-phase discharge and water in liquid-phase discharge. In this work, to make full use of the activation of auxiliary gases and maximize the energy utilization in liquid-phase discharge, the microwave liquid-phase plasma technology was used to study the activation of the CH4-H2O system by auxiliary gases for the first time, the photoelectric characteristics of discharge and discharge plasma parameters were analyzed. N-2 and Ar were selected as auxiliary gases. The results showed that auxiliary gas could also activate CH4 and H2O in addition to the effective dissociation of reactants by electron collision, and the discharge gas-phase products were mainly H-2. Compared with the discharge in the pure CH4-H2O system, under N-2 and Ar atmosphere, the hydrogen production energy efficiency increased by 43.0% and 72.8%, respectively. This difference is mainly related to the selectivity of the active species produced by the two auxiliary gases to the original reactants and radicals. This study provides a simple and efficient method for plasma-assisted CH4 activation for hydrogen production.