Quantifying Localized Surface Plasmon Resonance Induced Enhancement on Metal@Cu ₂ O Composites for Photoelectrochemical Water Splitting

The localized surface plasmon resonance (LSPR) of metal nanoparticles can substantially enhance the activity of photoelectrocatalytic (PEC) reactions. However, quantifying the respective contributions of different LSPR mechanisms to the enhancement of PEC performance remains an urgent challenge. In this work, Cu@Cu₂O composites prepared by annealing Cu₂O under an inert atmosphere and electrodeposited metal@Cu₂O composites (M_ED@Cu₂O, M_ED = Cu_ED, Au_ED, Ag_ED, Pd_ED, Pt_ED) are employed as platform materials to investigate the LSPR effect on the PEC hydrogen evolution reaction (HER). All the composites exhibited remarkably LSPR-enhanced activity toward PEC HER. The contributions of two LSPR mechanisms, plasmon induced resonance energy transfer (PIRET) and hot electron transfer (HET), to the photocurrent on Cu@Cu₂O and Cu_ED@Cu₂O are quantified by using different bands of incident light. Moreover, using M_ED@Cu₂O composites, the effects of both the metal species and the applied potential on HET are quantitatively investigated. The results reveal that a pronounced HET enhancement occurs only when the LSPR peak energy is lower than the semiconductor bandgap energy (E_g) and that HET strengthens as the applied potential becomes more negative for PEC HER. This work therefore provides a quantitative understanding of the roles of PIRET and HET in boosting PEC activity.