Suppressing Charge Recombination in Photoelectrochemical Cells from Plasmon-Induced Resonance Energy Transfer

The application of n-type metal-oxide based photoelectrode, such as hematite (α-Fe₂O₃) and bismuth vanadate (BiVO₄), for the photoelectrochemical (PEC) water splitting has been regarded as a promising approach for clean H₂ production because of their earth abundance and high stability in an aqueous electrolyte. However, their too short hole diffusion length, poor electrical conductance, and inferior oxygen evolution reaction (OER) kinetics deteriorate the PEC response, which limits to reach the theoretical maximum PEC water splitting performance.<br/>In this work, we introduced a 2D nanoamplifier metal film composed of an assembled globular Au nanosphere (AuNS) array with a highly ordered hexagonal pattern (hereafter, Au array) onto the surface of α-Fe₂O₃ film to enhance the PEC water oxidation through the plasmon-induced resonance energy transfer (PIRET). The Au array is self-assembled on the hexagonally patterned polyurethaneacrylate (PUA) pillar molds and transfer-printed on the surface of the photoanode. The Au array induced the near-field coupling interaction and amplified the electromagnetic field, thus promoting plasmonic energy transfer into the underneath film, resulting in efficient light harvesting in a broadband light spectrum and suppression of charge recombination, which increases the carrier lifetime. The long-lived photogenerated holes at the surface of photoanode were demonstrated from the transient absorption (TA) decay profile. Enhanced charge transfer efficiency was also investigated. Furthermore, the Au array was introduced on the surface of molybdenum-doped BiVO₄ film to demonstrate the high versatility of facile transfer printing Au arrays. Consequently, the transfer-printed Au array resulted in an efficient PIRET effect on both α-Fe₂O₃ and BiVO₄ films. An over 3.3-fold higher photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) was achieved for the Au array-incorporated α-Fe₂O₃ film. As for BiVO₄, Au array improved the photocurrent density by 1.5-fold more than bare photoanode.<br/>In conclusion, we introduced a 2D arranged Au array in a highly ordered hexagonal pattern onto the surface of α-Fe₂O₃ and BiVO₄ films via a facile transfer printing process and confirmed the enhanced PEC response through the PIRET effect. The rationally designed Au array film can provide a potential strategy for the versatile application in various light-mediated energy conversion and optoelectronic devices.