Valence state and redox property of Fe-CNTs added CeO2/TiO2 catalyst

Abstract

The investigation focused on examining the impact of incorporating Fe-carbon nanotubes (CNTs) on the valence state and oxygen vacancies, and the physicochemical parameters of the catalytic system. For the CeO₂/TiO₂ catalyst with Fe-CNTs, no distinct X-ray diffraction (XRD) peaks corresponding to Fe-CNTs were observed. This indicated their uniform dispersion, supported by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) imaging. X-ray photoelectron spectroscopy (XPS) analysis was conducted to observe the changes in the valence state due to the addition of Fe-CNTs. The concentration of Ce³⁺ on catalyst surface increased from 19.90% to 29.48% with an increased concentration of the chemisorbed oxygen species (O_α). This suggests that the addition of Fe-CNTs into CeO₂/TiO₂ catalyst reduced Ce⁴⁺ on the catalyst surface, resulting in the formation of oxygen vacancies. Oxygen temperature-programmed desorption (O₂-TPD) and hydrogen temperature-programmed reduction (H₂-TPR) analyses showed both the adsorbed oxygen species and H₂ consumption increased with adding Fe-CNTs. Furthermore, the onset temperatures for O₂ desorption and H₂ consumption became lower, confirming the enhancement of catalytic redox properties.