Abstract
Methane pyrolysis is emerging as a promising carbon-negative hydrogen production technique, offering an energy-efficient alternative to conventional methane steam reforming. A novel microwave discharge plasma (MDP) system is introduced to enhance methane pyrolysis, enabling the simultaneous production of carbon-negative hydrogen and high-quality carbon materials. Key operational parameters, including microwave power, flow rate, gas composition, and reactor geometry, have been systematically investigated for their significant effects on methane pyrolysis. Optimal system performance is achieved at 300 W microwave power and a flow rate of 0.07 m/s, yielding a methane conversion rate of 99.8 % and a specific energy requirement (SER) of 180 kJ/mol, with few-layer graphene produced as a valuable byproduct. The critical role of energetic electrons, argon species, and methane interactions in C–H bond cleavage and carbon nanostructure formation is elucidated through optical emission spectroscopy (OES) analysis. Additionally, density functional theory (DFT) calculations reveal the influence of microwave fields on methane adsorption energy over tungsten surfaces, shedding light on the mechanisms of methane cracking product formation. This study provides fundamental insights into MDP methane pyrolysis, advancing sustainable methane conversion and utilization strategies. © 2025 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.