Regulating Charge Separation Via Periodic Array Nanostructures for Plasmon‐Enhanced Water Oxidation

Abstract Plasmonic resonance intensity in metallic nanostructures plays a crucial role in charge generation and separation, directly affecting plasmon‐induced photocatalytic activity. Engineering strategies to enhance plasmonic effects involve designing specific nanostructures, such as triangular nanoplates with sharp corners or dimer nanostructures with hot spots. However, these approaches often lead to a trade‐off between enhanced plasmonic intensity and resonance energy, which ultimately determines local charge density and photocatalytic performance. Here, inspired by theoretical predications, it is shown that a flexibly controlled plasmonic photocatalyst, consisting of an ordered array of Au nanoparticles on a SrTiO 3 surface, exhibits an enhanced surface plasmon resonance (SPR) intensity while maintaining a constant SPR resonant energy, due to the presence of surface lattice resonance. This trade‐off results in improved charge separation efficiency and an increase in local charge density at catalytically active sites, as verified by theoretical simulations, surface photovoltage microscopy, and ultrafast transient absorption spectroscopy. Moreover, the optimized periodic photocatalyst shows a 7‐fold increase in water oxidation activity over disordered nanostructures. This work provides a novel approach for balancing the intensity and energy of SPR, which will contribute to optimizing photocatalytic activity on plasmonic platforms.