Application of Cu_xO-Fe_yO_z Nanocatalysts in Ethynylation of Formaldehyde.

ABSTRACT: Composite nanomaterials have been widely used in catalysis because of their attractive properties and various functions. Among them, the preparation of composite nanomaterials by redox has attracted much attention. In this work, pure Cu₂O was prepared by liquid phase reduction with Cu(NO₃)₂ as the copper source, NaOH as a precipitator, and sodium ascorbate as the reductant. With Fe(NO₃)₃ as the iron source and solid-state phase reaction between Fe³⁺ and Cu₂O, Cu_xO-Fe_yO_z nanocatalysts with different Fe/Cu ratios were prepared. The effects of the Fe/Cu ratio on the structure of Cu_xO-Fe_yO_z nanocatalysts were studied by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet confocal Raman (Raman), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS, XAES), and hydrogen temperature-programmed reduction (H₂-TPR). Furthermore, the structure-activity relationship between the structure of Cu_xO-Fe_yO_z nanocatalysts and the performance of formaldehyde ethynylation was discussed. The results show that Fe³⁺ deposited preferentially on the edges and corners of the Cu₂O surface, and a redox reaction between Fe³⁺ and Cu⁺ occurred, forming Cu_xO-Fe_yO_z nanoparticles containing Cu⁺, Cu²⁺, Fe²⁺, and Fe³⁺. With the increase of the Fe/Cu ratio, the content of Cu_xO-Fe_yO_z increased. When the Fe/Cu ratio reached 0.8, a core-shell structure with Cu₂O inside and a Cu_xO-Fe_yO_z coating on the outside was formed. Because of the large physical surface area and the heterogeneous structure formed by Cu_xO-Fe_yO_z, the formation of nonactive Cu metal is inhibited, and the most active species of Cu⁺ are exposed on the surface, showing the best formaldehyde ethynylation activity.

SUBMITTER: Li H 

PROVIDER: S-EPMC6781078 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature