Catalyst characterization and surface oxygen properties of Ag-Fe mixed oxide catalysts

Abstract

Ag-Fe mixed oxides catalysts with different Ag/Fe ratio are prepared by co-precipitation method. The catalysts have been characterized by X-ray diffraction (XRD). XRD shows that over all the catalysts exist as the σ-AgFeO₂ phase. The surface oxygen species of catalysts and the reduction properties of catalysts have been investigated by temperature-programmed decomposition (TPD) and reduction (TPR). It has been found that only one peak is observed on O₂- TPD profiles which is attributed to lattice oxygen from finely dispersed σ-AgFeO₂ phases. Three reducible peaks (α, β,γ) have been observed on H₂-TPR profiles. The α peak (around 180-220°C) is attributed to the reduction of the small phase of σ-AgFeO₂, β peak (around 250-280°C) is attributed to the reduction of the large phase of σ-AgFeO₂, and they peak is attributed to the reduction of Fe₂O₃ species. The results indicate that the Ag/Fe (1:1) catalyst exhibits highest oxidation activity in CO oxidation. It has been found that the σ-AgFeO₂ phase is the active site which makes main contribution in CO oxidation reaction.