Application of ZrO2-Based Hierarchical Nanofibers as a Promoter in Ni Catalyzed Methane Dry Re-Forming

In this work, the use of electrospun zirconia nanofibers (NFs), native and doped with 8% mol yttrium, was evaluated for the first time as supports for Ni-based hierarchical catalysts in the dry re-forming of methane (DRM). By a thermal annealing process of the as-made fibers to 500–1000 °C, we induce controlled changes to the NFs structural properties, before the introduction of a thin MgAlOx mixed oxide (MO) layer and nickel (Ni) to make hierarchical catalysts for DRM. Analyzing the NFs properties, we find that the grain size of the underlying supports have a strong monotonically increasing correlation to the DRM reaction performance. Specifically, we find that the increase in the ZrO2 or yttria stabilized zirconia (YSZ) grain size by 2–3 enhances the CH4 and CO2 conversions by a factor of 2. We attribute this effect to the efficiency of the contact between the thin MgAlOx MO layer and the underlying supports, and their joint effect on the Ni-catalyzed DRM. We show that the same enhancement does not occur when using a support material based on ZrO2 nanoparticles (NPs) rather than NFs. High-resolution transmission electron microscopy shows that the Ni NPs were exsolved from the MgAlOx MO thin layer to form a coke and sinter-resistant catalyst.