Controlling the Catalytic Efficiency on the Surface of Hollow Gold Nanoparticles by Introducing an Inner Thin Layer of Platinum or Palladium.

The efficiency of heterogeneous catalysis of electron-transfer reactions on the surface of gold nanoshells was changed by adding an inner platinum or palladium nanoshell in the double-shell nanocatalysts. The reduction of 4-nitrothiophenol (4NTP) by borohydride was studied as a model reaction. To confirm the heterogeneous catalytic mechanism, the nanocatalysts were assembled into a monolayer on the surface of a quartz substrate using the Langmuir-Blodgett technique, and the 4NTP was allowed to bind to the surface of gold through a strong thiol bond. The stages of the reduction reaction of 4NTP on the surface of gold were successfully followed by time-resolved surface-enhanced Raman spectroscopy. Palladium was found to increase the catalytic efficiency of the gold surface due to the presence of a new Fermi level of the palladium-gold alloy, while platinum decreased its catalytic efficiency due to the electron-withdrawing effect of platinum atoms, which resulted from the difference in their electrochemical reduction potentials.