Steering electron–hole migration pathways from plasmon-induced resonance energy transfer in hematite to enhance their photoelectrochemical water splitting

Abstract

The strategy of Plasmon-Induced Resonance Energy Transfer (PIRET) holds promise in mitigating the recombination of photo-generated electron-hole pairs, thereby amplifying the efficiency of an electrode in photoelectrochemical (PEC) reactions geared towards solar-driven PEC. Nevertheless, the PIRET mechanism, particularly from the view of charge separation and extraction dynamics, remains unclear. Herein, we examined PEC water splitting activities of Au nanoparticles decorated α-Fe2O3 nanoarrays (α-Fe2O3/Au NRs) and systematically investigated the PIRET mechanism by the combination of ultraviolet-visible spectra, field distribution simulation, and transient absorption spectroscopy. The PIRET effect of Au nanoparticles (NPs) generates a localized electromagnetic field near the surface of the α-Fe2O3 NRs and the significant near-field coupling between α-Fe2O3 NRs and Au NPs promotes cross-sectional absorption that markedly enhances plasmonic energy transfer from Au NPs to α-Fe2O3 NRs. TA measurement uncovers the proximate electric field around α-Fe2O3 NRs, which emanates from the Au NPs' PIRET, orchestrates the instantaneous segregation of electrons and holes upon their formation and births enduring photogenerated holes in α-Fe2O3/Au NRs. Additionally, the FeOOH overlayers, as cocatalyst, are effective in boosting hole transfer kinetics. Consequently, the photocurrent density exhibited by the α-Fe2O3/Au/FeOOH arrays is amplified by 3.5 times in comparison to the pristine α-Fe2O3 NR arrays.