Impact of Hot Carrier Dynamics on Photoelectrocatalytic Activity on Au@Pd Antenna-Reactor Nanoparticles

Photoinduced hot carriers generated from the decay of surface plasmons in noble metals play a decisive role in producing green hydrogen gas through the photoelectrochemical (PEC) water splitting reaction, a process driven by visible light absorption. To optimize the utilization of these hot carriers, we employed a plasmonic antenna-reactor model based on core-shell structured Au@Pd nanoparticles (NPs) with an ultrathin Pd shell. In this study, we demonstrate that TiO₂ nanotube arrays (TNAs) decorated with Au@Pd NPs exhibit superior performance with the Pd shell serving as a catalytic reactor that efficiently extracts hot carriers from the plasmonic Au antenna. The photocatalytic performance in PEC measurements increased with higher Pd coverage, and Au₇₀@Pd₃₀/TNAs exhibited a 2.2-fold higher photocurrent compared with bare Au/TNAs. The enhanced oxygen evolution reaction (OER) activity observed for Au₇₀@Pd₃₀/TNAs is attributed to the higher population of hot holes on the surface of Au@Pd NPs, which enhances the oxidation capability for interactions with electrolytes. Femtosecond transient absorption (fs-TA) spectra of Au@Pd NPs revealed a shorter lifetime of hot electrons through electron-phonon (e-p) scattering in Au₇₀@Pd₃₀ NPs compared to Au NPs, indicating suppressed charge recombination and increased hot hole population on the surface. Therefore, this study suggests that the plasmonic antenna-reactor model, critically influenced by hot carrier dynamics, provides a promising framework for efficient photoelectrocatalytic systems.