Tailoring Methane Pyrolysis and Carbon Products through Bubble Dynamics Regulation via Inlet Design in Molten Copper

Molten metal-catalyzed methane pyrolysis represents a promising route for low-carbon hydrogen production coupled with valuable carbon materials. However, the influence of methane bubble dynamics on interfacial reactions and carbon evolution remains poorly understood. Here, we demonstrate that bubble dynamics engineering can effectively regulate methane conversion and carbon structure formation in molten copper. By integrating computational fluid dynamics (CFD) simulations with experimental investigations, we reveal that the gas inlet configuration significantly alters bubble detachment, rising behavior, and residence time. The conventional straight inlet (I-type) generates relatively large bubbles that interact strongly with the nearby quartz wall, resulting in wall-guided bubble transport and a shorter rising path. In contrast, the curved inlet structure (U-type) promotes bubble detachment into the bulk molten Cu, leading to less wall-constrained and more tortuous bubble trajectories with longer residence times. The optimized bubble dynamics increase methane conversion to 12.11% and the carbon production rate to 0.74 g/h, while simultaneously improving the structural quality of the carbon products. These findings establish bubble dynamics as a key process parameter governing interfacial carbon supply and growth pathways, providing a scalable strategy for enhancing hydrogen and carbon coproduction in molten metal methane pyrolysis.