Plasma-driven templating: synergistic growth of tailored CNTs and CO_x-free H₂ from CH₄ over Ni catalysts

Conventional thermal or plasma-only methane decomposition suffers from numerous limitations in catalytic conversion and product formation, hindering efficient H₂ and CNTs co-production. Herein, a catalyst-assisted dielectric barrier discharge (DBD) plasma process over a Ni-based catalyst is reported that overcomes this limitation at a moderate temperature of 450 °C. With the catalyst positioned within the plasma discharge zone, the system simultaneously achieves relatively high CH₄ conversion and H₂ selectivity. Multi-scale characterization coupled with reactive molecular dynamics simulations reveals a dual role of plasma: as a reaction driver, plasma initiates the first C–H bond cleavage (CH₄→CH₃∗+H∗) while the catalyst surface mediates terminal dehydrogenation (M-CH→M-C+H∗), thereby suppressing hydrocarbon by-product formation; and as a nanostructure regulator, the plasma-induced triggers deformation of Ni nanoparticles, templating the tip-growth of multi-walled carbon nanotubes (MWCNTs) with a narrowed average diameter of 42.0 nm. The CNTs exhibit a graphitic structure with tunable defect density governed by plasma ion etching.