Highly efficient Co-added Ni/CeO2 catalyst for co-production of hydrogen and carbon nanotubes by methane decomposition

Abstract

The catalytic decomposition of methane (CDM) is a hydrogen and nanostructured carbon production process with minimal CO₂ emission. Among the transition metal-based catalysts (e.g. Ni, Fe, Co, etc.), Ni-based catalysts are most widely studied due to the higher catalytic activity in decomposing methane. However, the limited lifespan of the catalyst makes it unsuitable for practical applications. Effective methane decomposition catalysts should be designed to optimize both reaction efficiency and catalyst lifetime. A Ni/CeO₂ catalyst, developed in previous studies, Co was added to promote low-temperature (< 700 °C) activity manipulating the redox property of Co. Among the prepared catalysts with varying Ni:Co ratio, the methane conversion rate of the Ni₈Co₂/CeO₂ catalyst was approximately twice that of the Ni₁₀/CeO₂ catalyst, confirming its excellent low-temperature activity. The reaction rate of Ni₈Co₂/CeO₂ catalyst was 4.38 mmol/min∙g_cat at 600 °C with WHSV of 36 L/g_cat∙h. In terms of characteristics of carbon products, Raman spectroscopy analysis revealed that the carbon grown on the catalyst surface exhibited high crystallinity, with D-G band ratio (I_D/I_G) of 1.01. The fresh and used catalyst samples were characterized by TEM, XPS, XAS, and other methods to analyze the parameters affecting catalytic activity.