Hierarchically structured nanospherical fibrous silica-supported bimetallic catalysts: An enhanced performance in methane decomposition for simultaneous production of hydrogen and carbon nanomaterials

Title : Hierarchically structured nanospherical fibrous silica-supported bimetallic catalysts: An enhanced performance in methane decomposition for simultaneous production of hydrogen and carbon nanomaterials

Abstract:

Catalytic methane decomposition is an encouraging method for hydrogen production, also enabling the formation of valuable carbon nanomaterials that can be utilized in, transportation fuels, chemical synthesis, and fuel cell technology. In this study, bimetallic 3d transition metal (Ni, Fe, Co) catalysts supported on spherical mesoporous nanofibrous silica KCC1 were successfully synthesized using a hydrothermal method followed by sono co-impregnation. The catalysts were evaluated for their efficacy in the catalytic decomposition of methane. Comprehensive characterization of the catalysts was conducted utilizing XRD, FTIR, SEM, TEM, STEM, XPS, H₂-TPR, and BET techniques. XRD and TEM analyses confirmed the formation of Ni-Fe, Ni-Co, and Co-Fe bimetallic alloys on the fibrous silica without compromising its dendrimeric hierarchical structure. STEM HAADF mapping revealed a uniform dispersion of bimetallic nanoparticles within the spherical fibrous framework. Catalytic tests demonstrated that all bimetallic catalysts exhibited high activity and stability for methane decomposition at 700 °C over 180 minutes of time on stream. Among them, Fe-based catalysts (Ni–Fe/KCC1 and Co–Fe/KCC1) achieved the highest hydrogen yields of 80% and 60%, respectively. Methane conversion was 1.56 and 2.23 times higher in Ni-Fe/KCC1 compared to Co-Fe/KCC1 and Ni-Co/KCC1, respectively. Post-reaction characterization of the spent catalysts was performed using XRD, Raman spectroscopy, SEM, TEM, and TGA. The degree of graphitization and crystallinity of carbon nanotubes (CNTs) formed on the catalysts was determined through XRD and Raman analyses and correlated with catalyst properties. TEM analysis provided insights into the structural morphology (chain-like or parallel-wall type) and growth mechanism (tip or base growth) of the CNTs. TGA analysis confirmed the absence of amorphous carbon formation during methane decomposition over all bimetallic catalysts.

Biography:

Currently, Rizwan Ali is a Ph.D. scholar at the Department of Chemical and Petroleum Engineering, Khalifa University (UAE), passionate about developing novel catalytic materials for simultaneous hydrogen production and carbon nanomaterials. He received his MSc degree from University of Engineering and Technology (Lahore) Pakistan in 2018, specializing in the research area of developing valuable adsorbents for toxic pollutant removals by using cheap waste raw materials. He began his teaching career as a Lecturer in University of Engineering and Technology, Lahore, Pakistan. His primary areas of investigation include methane, hydrogen, carbon nanomaterials, chemical reaction engineering, thermocatalytic cycle and inorganic chemistry. He has published several research articles in SCI journals.