Intensified near-field by localizing surface plasmon for enhancing photoelectrochemical responses via periodically patterned Au assemblies

The introduction of plasmon induced energy transfer (PIET) is a promising approach to enhance the photo-electrochemical (PEC) responses on metal-oxide based photoelectrodes. Most approaches of harnessing surface plasmon resonance use metal nanoparticles (NPs) spread over the electrode surface. However, crucial challenges remain for exploiting the strongly amplified near-field by coupling the NPs and underlying photoelectrodes. Herein, we demonstrate effective localization of a plasmon-induced near-field on a photoelectrode via patterned Au NP assemblies (Au-PAT) that improves the PEC responses for efficient oxidation reactions in aqueous elec-trolytes. The coupling effect between Au-PAT and the hematite (alpha-Fe2O3) photoanode promoted the photoex-citation of charge carriers around the space charge region. We computationally analyzed the plasmonic effects boosted by Au-PAT and found that Au-PAT with an optimized grating pitch enhanced the light absorption ef-ficiency and increased the interband transition rate via PIET. Consequently, the effective surface near-field induced by the rationally designed Au-PAT suppressed the undesired surface charge recombinations and enhanced the charge transfer, resulting in a 1.9-fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE). Furthermore, the near-field effect was also effective for the PEC hydrazine oxidation reaction, with 3.2-fold increased photocurrent density at 1.23 V versus RHE. This demonstrates that imple-menting Au-PAT is a versatile strategy as an application for various PEC reactions.