Atomic Layer Deposition-Assisted Synthesis of Embedded Vanadia Catalysts

Catalyst–support interactions are known to be of great importance for the performance of supported oxide catalysts such as supported vanadia. With the aim of enhancing the oxide–support interactions, we propose a strategy for the controlled synthesis of embedded oxide catalysts using atomic layer deposition (ALD). As demonstrated for vanadia (VOx), the synthesis is based on the sequential deposition of VOx and the "support" material (Al2O3, SiO2, TiO2) onto graphene oxide, which serves as a sacrificial carrier matrix facilitating the embedding of VOx, followed by template removal by calcination or ozone treatment. Detailed characterization of the synthesis process and the final catalysts is carried out using multiple spectroscopic (Raman, UV–vis, XPS), thermogravimetric, and electron-microscopic (TEM, EELS) analyses. The successful formation of a VOx–support interphase is confirmed by UV Raman spectroscopy. Despite the high loadings (LV > monolayer coverage) of accessible sites, the embedded VOx is present in a dispersed state in the case of the ozonolyzed samples. Structural models are proposed to account for the observed behavior. The activity of the embedded VOx catalysts is verified in the oxidative dehydrogenation (ODH) of ethanol and compares favorably with reported data on conventional supported catalysts. Compared to the literature, the ozonolyzed VOx/Al2O3 catalysts show a significantly improved performance, whereas the VOx/SiO2 catalysts define a benchmark. Our results demonstrate the feasibility of rational catalyst engineering of supported oxide catalysts.