Surface growth of mixed metal oxide thin rafts and their impact on methane dry reforming

Abstract

Synergistic interactions between the supported thin oxide layer and the underlying metal oxide support led to the development of novel and exciting material properties. In this work, we present a new and general approach for the surface growth of MgAl layered double hydroxides (LDH) on ZrO₂, Al₂O₃, and TiO₂ support materials. We examine the synergistic interactions between the top MgAlO_x mixed metal oxide (MMO), obtained after LDH calcination, and the underlying metal oxide support (MMO/metal oxide) as a function of MMO loading and support type. The obtained materials are characterized using a range of analytical tools ICP-OES, H₂-TPR, CO₂-TPD, PXRD, TGA/DSC, physisorption, HRSEM-EDS and HAADF-STEM–EDS followed by catalytic testing. We show that regardless of the MMO/metal oxide combination, effective interaction between the MMO and the underlying support, more dominant at the lower MMO coverage, promotes synergistic effects, manifested by a lower Ni reduction temperature compared to Ni on bulk MMO. Evaluating the obtained catalysts (Ni/MMO/metal oxide) in the dry reforming of methane (DRM) reaction, we find that the increase in MgAlO_x-MMO coating amount on the ZrO₂ nanoparticles (NPs) leads to an improvement in DRM activity and stability. In addition, we find that for the same MgAlO_x-MMO coating amount, the Ni catalyst based on the ZrO₂ NPs is superior to the catalyst based on Al₂O₃ NPs, while the catalyst based on TiO₂ NPs is the least active. The obtained results are explained in context to the extent of coating, metal support interaction (MSI) levels, and support structure. Combined with the high versatility of LDH material, this new methodology provides a versatile synthetic route to adapt the surface property of an oxide to a certain application. For DRM, we show the tuning of MSI as governed by the interactions between the underlying metal oxide and supported MMO.