Formation of interfacial Fe–O–Si bonds between silica and different iron oxides

Interaction between iron oxides and silica play an important role in the stability and activity of iron -based catalysts in Fischer–Tropsch synthesis (FTS). It has been reported that the formation of Fe–O–Si bond is related to Fe–SiO 2 interaction and responsible of the dispersion and stability of iron catalysts with silica as support or structure promoter. In this work, we investigate the growth of silica on FeO- and α–Fe 2 O 3 films on Pt(111) using low energy electron diffraction (LEED), scanning tunneling microscopy (STM), reflection–absorption infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy (XPS). The results show that the silica structure exhibits a strong dependence on the underlying iron oxide surfaces. On FeO film, the RAIRS band at 1005 cm −1 and the component at 530.6 eV in O 1 s XPS suggest that silica forms monolayer and bonds to underlying FeO through Fe–O–Si linkages. STM results show that the silica monolayer possesses well-defined honeycomb structure. In contrast, silica grown on Fe 2 O 3 tends to form three-dimensional clusters and only a small portion of silicon forming Si–O–Fe bond, suggested by an apparent peak at 1240 cm −1 and a small feature at 1005 cm −1 . These results indicate that interfacial structure between silica and iron oxides are dominated by the phase of iron oxides. Si–O–Fe bonds is easy to form on FeO film but not on Fe 2 O 3 film. This work provides an atomistic view of iron silicate interface formation and offers insights into the role of silica in iron-based catalysts and other functional materials.