Anti-sintering Au nanoparticles stabilized by a Fe-incorporated MgAl2O4 spinel for CO oxidation

Abstract

The development of sintering resistant gold nanocatalysts is one of the central tasks in gold catalysis. In this regard, the influence of lattice spacing of a spinel support on the thermal stability of immobilized gold nanoparticles (NPs) was investigated. Accordingly, MgAl₂O₄ (MAO) and MgAl_1.2Fe_0.8O₄ (MAFO) spinels, whose face-centered cubic (FCC) oxygen sub-lattice is smaller and larger than the gold FCC lattice, respectively, were explored for thermal stability studies. Au/MAO catalyst exhibits a significant increase in the size of Au NPs from ∼2.5 to ∼8.4 when the calcination temperature increases from 120 °C to 500 °C. In contrast, Au/MAFO catalyst retained the size of Au NPs (∼2.7 nm) when calcined up to 500 °C. Such significant enhancement in the stability of gold nanoparticles indeed helps to preserve their catalytic activity towards CO oxidation, which is related to the size effect besides the well-known support effect. The presence of water in the reaction stream was found to have a promotional effect on the catalytic activity. These studies can open up the applications of gold nanocatalysts at high temperatures.