Carbon nanostructure formation over Ni, Co, Fe on γ-Al2O3 during low-temperature dry reforming of methane: insights into mechanisms and catalytic behaviour

Abstract

The study presents an investigation of the influence of transition metal phases – Ni, Co, and Fe – on γ-Al₂O₃-supported catalytic systems on catalytic performance and formation of nanostructured carbon allotropes during low-temperature (500–600 °C) dry reforming of methane (DRM). The synthesised catalysts were comprehensively characterised by AAS, BET, BJH, NH₃– and CO₂-TPD, H₂-TPR, in situ XPS, and in situ XRD. Catalytic performance was evaluated by GC-TCD monitoring of reactant conversion and syngas yield. Carbon products were analysed by TOC, O₂-TPO, Raman spectroscopy, XRD, and SEM-EDX. Ni/γ-Al₂O₃ displayed excellent performance at both temperatures with noticeable formation of filamentous carbon structures. Co/γ-Al₂O₃ exhibited the highest activity along with the greatest carbon deposition with a graphitic morphology. Fe/γ-Al₂O₃ demonstrated marginal catalytic activity and zero carbon formation, associated with its limited reducibility. The study reveals that metal reducibility governs catalytic activity, while metal-specific carbon growth mechanisms determine catalyst stability, providing insights into the rational catalyst design in low-temperature DRM processes.