Preparing uniform supported Pd-Ni catalysts with citrate-assisted impregnation

• Published in: Journal of catalysis 2024-08, Vol.436, p.115624, Article 115624
• Main Authors: Helfferich, Kristiaan H., Fabrie, Charles A., Meeldijk, Johannes D., Tierney, George F., van der Hoeven, Jessi E.S., van den Brink, Peter J., de Jong, Krijn P., de Jongh, Petra E.
• Format: Article
• Language: English
• Subjects: Bimetallic catalyst; Heterogeneous catalysis; Pd-Ni
• ISSN: 0021-9517
• DOI: 10.1016/j.jcat.2024.115624

[Display omitted] •Uniform Ni precursor distribution was realized using citric acid as revealed with cryo transmission electron microscopy.•Uniform bimetallic nanoparticles were produced using co-impregnation of Pd precursors with Ni citrate.•Pd(OAc)2 produced segregated Pd and Ni phases whereas Pd(NH3)4(NO3)2 produced bimetallic Pd-Ni nanoparticles.•CO2 hydrogenation activity reflected the Pd-Ni intimacy. 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.