Dual photolytic pathways in an alloyed plasmonic near-perfect absorber: implications for photoelectrocatalysis

Plasmonic noble metal nanoparticles exhibit intense interactions with light but are inherently chemically unreactive. Alloying plasmonic gold with catalytic palladium forms a hybrid catalyst incorporating each metal's benefits. In this work we demonstrate a robust method for preparing alloyed nanoparticles without the need for colloidal synthesis or time-consuming lithography. This method results in uniform, densely packed monolayers of alloyed AuPd nanoparticles suitable for inclusion in electromagnetic perfect absorbers, which further strengthen existing light-matter interactions. While these materials demonstrate a strong photocathodic response not possible using monometallic Au nanoparticles on a n-type spacer and exhibit higher photon-to-energy efficiencies than Pd analogues, they are also capable of a photoanodic response characterized by electron injection across the Schottky junction with TiO2. The alloying of plasmonic Au and catalytic Pd and subsequent incorporation in a highly absorbing material represents a promising step toward efficient photoelectrocatalysts for hydrogen production that operate under real-world conditions.