A new preparation strategy via an in situ catalytic process: CeO2@Ag/Ag2Ta4O11 catalyst for 4-nitrophenol reduction

Abstract

A novel catalyst, CeO₂@Ag/Ag₂Ta₄O₁₁, was successfully assembled via an in situ catalytic process for 4-nitrophenol reduction. As-prepared samples were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray spectroscopy (XPS), and ultraviolet-visible diffuse reflection spectroscopy (DRS). The results showed the elementary substance Ag was produced from Ag₂Ta₄O₁₁ after a circular reduction reaction and was homogeneously deposited on the surface of Ag₂Ta₄O₁₁ nanoparticles, which were wrapped by octahedron-shaped CeO₂. The as-prepared nanocomposites exhibited extremely accelerated catalytic activity toward the efficient reduction of 4-nitrophenol compared to pure CeO₂ and Ag₂Ta₄O₁₁ nanoparticles. 15 rounds of recycling experiments confirmed that the samples exhibited good reuse stability, assigned to the confined robust shield of CeO₂. The shell of CeO₂ efficiently prevented undesirable aggregation and leaching of Ag nanoparticles. The persistent ascending activity with an increasing number of experimental runs was related to the amount of metallic Ag gradually growing. Moreover, it was proposed that the active interfacial contact between ceria oxide/metallic Ag/the semiconductor Ag₂Ta₄O₁₁ (CeO₂@Ag/Ag₂Ta₄O₁₁) in the core–shell structure facilitated the transfer of electrons, contributing to the enhanced activity.