Catalytic decomposition of methane for controllable production of carbon nanotubes and high purity H2 over LTA zeolite-derived Ni-based yolk-shell catalysts

Catalytic decomposition of methane to produce H2 of high purity along with high value-added carbon nanotubes (CNTs) is a promising clean energy-conversion method but presents significant challenges in terms of the controllable production of CNTs. Herein, we report a structure-reconstruction strategy based on microporeconfined process to prepare LTA zeolite-derived yolk-shell catalysts with highly dispersed metallic nickel with particle sizes controlled between -7 to -23 nm. The nickel particle sizes have close relationship to the rates of methane decomposition/ penetration of dissolved carbon/ growth of CNTs, which greatly influences the catalytic performance. To confirm this relationship, we present molecular dynamics simulations to realize the tip-growth of multi-walled CNTs (MWCNTs) on nickel particles for the first time and are set apart from previous simulation works that were mainly focused on the base-growth of single-wall CNT. The simulations in our present work exhibit the evolution of metallic Ni active sites paired with the formation of MWCNTs, which proves the penetration process of dissolved carbon on metallic nickel clusters and provides a significant route for the design of functionalized CDM catalysts.