Site Communication in Direct Formation of H 2 O 2 over Single-Atom Pd@Au Nanoparticles.

Single atom alloy catalysts offer possibilities to obtain turnover frequencies and selectivities unattainable by their monometallic counterparts. One example is direct formation of H 2 O 2 from O 2 and H 2 over Pd embedded in Au hosts. Here, a first-principles-based kinetic Monte Carlo approach is developed to investigate the catalytic performance of Pd embedded in Au nanoparticles in an aqueous solution. The simulations reveal an efficient site separation where Pd monomers act as active centers for H 2 dissociation, whereas H 2 O 2 is formed over undercoordinated Au sites. After dissociation, atomic H may undergo an exothermic redox reaction, forming a hydronium ion in the solution and a negative charge on the surface. H 2 O 2 is preferably formed from reactions between dissolved H + and oxygen species on the Au surface. The simulations show that tuning the nanoparticle composition and reaction conditions can enhance the selectivity toward H 2 O 2 . The outlined approach is general and applicable for a range of different hydrogenation reactions over single atom alloy nanoparticles.