Intermetallic compounds, i.e., phases containing two or more metallic elements, are often efficient catalysts with higher activities than their separate components. However, their synthesis often requires high temperatures, which makes it difficult to control the size, shape, and surface area of the catalyst.

Wenyu Huang, Iowa State University, Ames, USA, and colleagues have synthesized intermetallic nanoparticles with defined sizes by confining them in an inorganic shell that withstands high temperatures. The team first synthesized seed platinum nanoparticles protected by mesoporous silica (Pt@mSiO₂), added the second metal (Sn, Pb, or Zn) in solution, and heated the reaction mixture for two hours. Subsequently, the samples were annealed at 600 °C to give the intermetallic nanoparticles. The silica shells protected the particles against aggregation during the annealing, but allowed the formation of the intermetallic phases due to their porosity.

The resulting catalysts were tested in the hydrogenation of furfural to furfuryl alcohol, and showed high activity and selectivity. Additionally, they were stable for at least 40 hours under the reaction conditions. PtSn@mSiO₂ showed the best catalytic performance of the synthesized intermetallic phases. It converted about 99 % of furfural, compared to 24 % for an equivalent amount of the monometallic Pt@mSiO₂.

• A Ship-in-a-Bottle Strategy To Synthesize Encapsulated Intermetallic Nanoparticle Catalysts: Exemplified for Furfural Hydrogenation,
  Raghu V. Maligal-Ganesh, Chaoxian Xiao, Tian Wei Goh, Lin-Lin Wang, Jeffrey Gustafson, Yuchen Pei, Zhiyuan Qi, Duane D. Johnson, Shiran Zhang, Franklin (Feng) Tao, Wenyu Huang,
  ACS Catal. 2016.
  DOI: 10.1021/acscatal.5b02281