Initial nucleation of platinum clusters after reduction of K2PtCl4 in aqueous solution: A first principles study

The initial nucleation of platinum clusters after the reduction of K2PtCl4 in aqueous solution is studied by means of first principles molecular dynam ics simulations. A reaction mechanism leading to a Pt dimer is revealed bot h by gas-phase simulations and by simulations which model the solution envi ronment. The key step of the observed reaction process is the formation of a Pt-Pt bond between a Pt(I) complex and an unreduced Pt(II) complex. In li ght of this result, we discuss the reduction process leading to the formati on of platinum nanoparticles. In the generally accepted model, the nucleati on of Pt particles starts only when a critical concentration of Pt(0) atoms is reached. Here, we discuss a complementary mechanism where metal-metal b onds form between Pt complexes in higher oxidation states. This is consiste nt with a number of experimental results which show that a high concentrati on of zerovalent atoms is not necessary to start the nucleation.