Extra electric field-enhanced lightning rod effect in pine needle-like Au microarrays for boosting direct plasmon-driven photoelectrochemical hydrogenation reactions via in-situ SERS monitoring

Abstract

Based on plasmonic metallic nanomaterials (NMs) with unique local surface plasmon resonance (LSPR), the photo-excited hot carrier-driven hydrogenation reaction becomes a new family of photocatalytic transformations in recent years. However, the high work function and rapid hot-carrier recombination of plasmonic NMs create huge barriers for widespread practical application. Herein, we propose a fascinating reactor of up-regulated electrochemical LSPR (EC-LSPR) driven hydrogenation reaction via the construction of hierarchical Au pine needles (H-Au PNs) with enhanced lightning rod effect under appropriate extra electric field. The plentiful elongated Au branches with sharp corners and edges can be served as excellent electron-transport channels for facilitating photo-excited hot carrier transmission and accelerating hot electron collection at nano-tips after plasmon decay. Additionally, the extra electric field with the applied voltage of − 0.8 V further improves the surface charge density and the internal polarization of H-Au PNs, boosting the separation efficiency of hot carriers as well as reducing the photoelectrochemical (PEC) potential on H-Au PNs. It directly leads to an effective activation enthalpy reduction to reach above the energy threshold of water splitting, which can achieve the direct plasmon-driven PEC-hydrogenation conversion of 4-nitrothiophenol (4-NTP) to 4-aminothiophenol (4-ATP) in aqueous solution, and the conversion rate constant is about 5 times higher than bare EC-driven conversion. The present work provides a new opportunity for the emerging direct plasmon-driven hydrogenation reaction.