Abstract

The structure of Pd–Ag/Al₂O₃ samples with different Ag/Pd ratios has been studied by a complex of physicochemical methods (H₂-TPR, XRD, H₂-TPD, TEM). Catalysts have been synthesized by supporting an active component on α-Al₂O₃ and γ-Al₂O₃. X-ray diffraction analysis has revealed the formation of a Pd–Ag substitutional solid solution with a face-centered cubic crystal lattice owing to alloying of the Pd and Ag components. An increase in the Ag content in the composition of bimetallic nanoparticles hinders the formation of palladium hydride (PdH_x), which is completely suppressed at a ratio of Ag/Pd > 0.5. Infrared spectroscopy of adsorbed CO has revealed the formation of single-atom Pd₁ sites on the surface of supported Pd–Ag bimetallic nanoparticles isolated from each other by silver atoms. Analysis of the structural stability of isolated Pd₁ sites has shown that, under conditions of CO adsorption at 150°C, the stability of the sites can be provided by an increase in the Ag/Pd ratio to ≥2.

中文翻译：

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Pd–Ag / Al 2 O 3双金属催化剂表面形成孤立的单原子Pd 1位点

摘要

通过多种物理化学方法（H ₂ -TPR，XRD，H ₂ -TPD，TEM）研究了具有不同Ag / Pd比的Pd-Ag / Al ₂ O ₃样品的结构。催化剂已经通过上的α-Al支撑的活性成分合成₂ ö ₃和γ-Al系₂ ö ₃。X射线衍射分析表明，由于Pd和Ag成分的合金化，形成了具有面心立方晶格的Pd-Ag替代固溶体。双金属纳米粒子组成中Ag含量的增加阻碍了氢化钯（PdH _x），当Ag / Pd> 0.5时被完全抑制。吸附的CO的红外光谱显示，在被银原子相互隔离的负载的Pd-Ag双金属纳米颗粒表面上形成了单原子Pd ₁位点。对分离的Pd ₁位点的结构稳定性的分析表明，在150°C的CO吸附条件下，可以通过将Ag / Pd比增加到≥2来提供位点的稳定性。