Site Communication in Direct Formation of H₂O₂ over Single-Atom Pd@Au Nanoparticles

Single atom alloycatalysts offer possibilities to obtain turnoverfrequencies and selectivities unattainable by their monometallic counterparts.One example is direct formation of H2O2 fromO(2) and H-2 over Pd embedded in Au hosts. Here,a first-principles-based kinetic Monte Carlo approach is developedto investigate the catalytic performance of Pd embedded in Au nanoparticlesin an aqueous solution. The simulations reveal an efficient site separationwhere Pd monomers act as active centers for H-2 dissociation,whereas H2O2 is formed over undercoordinatedAu sites. After dissociation, atomic H may undergo an exothermic redoxreaction, forming a hydronium ion in the solution and a negative chargeon the surface. H2O2 is preferably formed fromreactions between dissolved H+ and oxygen species on theAu surface. The simulations show that tuning the nanoparticle compositionand reaction conditions can enhance the selectivity toward H2O2. The outlined approach is general and applicable fora range of different hydrogenation reactions over single atom alloynanoparticles.