Production of multilayer graphene using molten Sn–Ni alloy as catalyst in a bubble column

The economical manufacturing of high-quality graphene has been a significant challenge in its large-scale application. Previously, we used molten Sn and Cu as the heat-transfer agent to produce multilayer graphene on the surface of gas bubbles in a bubble column. However, element Sn and Cu have poor catalytic activity toward methane pyrolysis. To further improve the yield of graphene, we have added active Ni into Sn to construct a Sn–Ni alloy in this work. The results show that Sn–Ni alloy is much more active for methane pyrolysis, and thus more graphene is obtained. However, the graphene product is more defective and thicker because of the faster growth rate. By using 300 ml molten Sn–Ni alloy (70 mm height) and 500 sccm source gas (CH₄:Ar = 1:9), this approach produces graphene with a rate of 0.61 g/hr and a conversion rate of methane to carbon of 37.9% at 1250 ℃ and ambient pressure. The resulting graphene has an average atom layer number of 22, a crumpled structure and good electrical conductivity.