Unraveling Plasmonic Field Contributions in Catalysis with Au@Al 2 O 3 ‐Pd‐Au@Al 2 O 3 Trimer Arrays

Plasmonic catalysis employs nanomaterials to mediate the conversion of photon energy into localized electromagnetic fields, hot carriers, and thermal energy, facilitating molecular transformations under mild conditions. Understanding the mechanisms governing plasmonic effects is crucial for optimizing the yield and selectivity in plasmonic catalysis. However, challenges persist in elucidating the role of plasmonic field effects due to the complex interactions among various contributing mechanisms. This study introduces Au@Al 2 O 3 ‐Pd‐Au@Al 2 O 3 trimer arrays to decouple plasmonic field effects from other influences. The alumina coating on the Au particles prevents charge transfer between gold and reactants, enabling focused examination of the field effects on Pd catalysts. Employing real‐time monitoring with liquid‐state surface‐enhanced Raman scattering (SERS), this work investigates the catalytic efficiency and kinetics of the C─C coupling reactions on palladium by tuning the near‐field strengths. Polarization‐dependent studies reveal that strong near‐field intensity around the trimer structures is amplified by ≈60‐fold under optimized conditions. The findings offer insights for optimizing catalytic reaction conditions and designing more effective composite plasmonic catalysts.