Reinforcing hydrogen and carbon nanotube co-production via Cr–O–Ni catalyzed methane decomposition†
Abstract
Catalytic methane decomposition shows the prominent superiority of generating hydrogen in one step with almost no carbon oxide production; however, it suffers from catalyst deactivation and low by-product carbon quality. Herein, a series of H2-reduced NixCr2Ox+3 (abbreviated as reduced NixCr2) catalysts were designed and synthesised for highly efficient methane decomposition and carbon nanotube production. A maximum methane conversion of 87.1% and hydrogen concentration of 91.8 vol% were achieved at 750 °C without deactivation. The results from XPS, XAS, and Raman reveal that the reduced NixCr2 catalysts have significant activity and stability. On the one hand, they form the Cr–O–Ni structure, thus possessing strong Ni–Cr2O3 interaction. On the other hand, the lattice oxygen of the reduced NixCr2 catalysts induces methane activation, thus accelerating methane activation, as demonstrated by the generation of a little amount of CO. In addition, the relationship between the types of carbon deposited and Ni/Cr ratio, decomposition temperature, and time was also revealed to guide carbon nanotube synthesis. Density functional theory calculation confirms the lowest dehydrogenation barrier of Ni(111)/Cr2O3(012), demonstrating the superiority of the Cr–O–Ni catalyzed methane decomposition. These findings provide innovative ideas for the construction of functionalized materials, which will substantially promote the development of methane decomposition.