Bimetallic supported catalysts can show synergistic effects compared to their monometallic constituents. However, it is challenging to produce bimetallic catalysts with a uniform nanoparticle distribution over the support, while ensuring each nanoparticle contains both metals. A promising strategy is to use impregnation precursors that facilitate uniform distribution of both metals over a support. In this work, citrate-based precursors were studied to prepare bimetallic Pd-Ni nanoparticles supported on SBA-15 mesoporous silica. Amongst others, cryo-electron microscopy demonstrated the excellent distribution of Ni citrate precursor after drying. Co-impregnation with Ni citrate precursor and Pd(OAc)2 or Pd(NH3)4(NO3)2 produced well-distributed Pd-Ni nanoparticles with a narrow particle size distribution. Extensive characterization with STEM-EDX, EXAFS and TPR showed that the type of Pd precursor controlled the Pd to Ni nanoscale intimacy. CO2 hydrogenation experiments demonstrated that increasing Pd-Ni intimacy decreased the activity. Our strategy to produce uniform Pd-Ni nanoparticles using citric acid is relevant also for other bimetallic systems.

中文翻译：

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柠檬酸盐辅助浸渍制备均匀负载型 Pd-Ni 催化剂


与单金属成分相比，双金属负载型催化剂可以表现出协同效应。然而，生产在载体上具有均匀纳米粒子分布的双金属催化剂，同时确保每个纳米粒子含有两种金属是具有挑战性的。一种有前途的策略是使用促进两种金属在载体上均匀分布的浸渍前体。在这项工作中，研究了基于柠檬酸盐的前体来制备负载在 SBA-15 介孔二氧化硅上的双金属 Pd-Ni 纳米颗粒。其中，冷冻电子显微镜证明柠檬酸镍前体在干燥后具有良好的分布。用柠檬酸镍前驱体和 Pd(OAc)2 或 Pd(NH3)4(NO3)2 共浸渍产生了分布良好、粒径分布窄的 Pd-Ni 纳米粒子。通过 STEM-EDX、EXAFS 和 TPR 进行的广泛表征表明，Pd 前驱体的类型控制着 Pd 与 Ni 纳米级的亲密度。 CO2 氢化实验表明，增加 Pd-Ni 亲密度会降低活性。我们使用柠檬酸生产均匀的 Pd-Ni 纳米粒子的策略也适用于其他双金属系统。