Stable Ni–Cu hollow-wall catalysts prepared by electroless plating for high-temperature methane decomposition: alloy durability and carbon deposition behaviour

Abstract

In this study, we investigated the high-temperature performance and stability of a Ni–Cu hollow-wall structured catalyst prepared by electroless plating (ELP) for catalytic methane decomposition (CMD). The catalysts were characterized by FE-SEM, SEM-EDX, XRF, XRD, HAADF-STEM, and Raman spectroscopy. Among the compositions tested, the Ni₇₀Cu₃₀ catalyst exhibited the best performance, showing a stable 39.8% methane conversion over 50 hours on steam at 650 °C and achieving a carbon yield of 958 g C per g Ni—values that exceed previously reported benchmarks. At this reaction temperature, the catalyst's hollow walls preserved their morphology (as confirmed by HAADF-STEM) while producing moderately ordered carbon fibres with potential nanomaterial applications. Increasing the reaction temperature further improved carbon quality, yielding well-graphitised nanotubes; however, it also shortened the catalyst life, as temperature-induced agglomeration resulted in larger alloy particles and reduced catalytic activity. Atomic erosion, particle fragmentation, Ni dissolution into carbon, Cu masking, alloy sintering, and carbon encapsulation of active sites were identified as the primary deactivation factors. This study provides insight into the role of Cu in ELP Ni–Cu catalysts and underscores the promising potential of the Ni₇₀Cu₃₀ hollow-wall structured catalyst for long-term turquoise-hydrogen production and solid-carbon capture via the CMD reaction.