  Alloyed metal nanoparticles are a promising platform for plasmonically
enabled hot-carrier generation, which can be used to drive photochemical
reactions. Although the non-plasmonic component in these systems has been
investigated for its potential to enhance catalytic activity, its capacity to
affect the photochemical process favorably has been underexplored by
comparison. Here, we study the impact of surface alloy species and
concentration on hot-carrier generation in Ag nanoparticles. By
first-principles simulations, we photoexcite the localized surface plasmon,
allow it to dephase, and calculate spatially and energetically resolved
hot-carrier distributions. We show that the presence of non-noble species in
the topmost surface layer drastically enhances hot-hole generation at the
surface at the expense of hot-hole generation in the bulk, due to the
additional d-type states that are introduced to the surface. The energy of the
generated holes can be tuned by choice of the alloyant, with systematic trends
across the d-band block. Already low surface alloy concentrations have a large
impact, with a saturation of the enhancement effect typically close to 75% of a
monolayer. Hot-electron generation at the surface is hindered slightly by
alloying but here an judicious choice of the alloy composition allows one to
strike a balance between hot electrons and holes. In this context, it is also
important to consider that increasing the alloy concentration broadens the
localized surface plasmon resonance, and thus decreases hot-carrier generation
overall. Our work underscores the promise of utilizing multicomponent
nanoparticles to achieve enhanced control over plasmonic catalysis, and
provides guidelines for how hot-carrier distributions can be tailored by
designing the electronic structure of the surface through alloying.
