Single atom alloy
catalysts offer possibilities to obtain turnover
frequencies and selectivities unattainable by their monometallic counterparts.
One example is direct formation of H2O2from
O2and H2over 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 H2dissociation,
whereas H2O2is 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. H2O2is 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 H2O2. The outlined approach is general and applicable for
a range of different hydrogenation reactions over single atom alloy
nanoparticles.