Expanding the Plasmonically Activated Volume for Enhanced Fast Carrier Extraction in Au/CeO2 Photocatalysts

Plasmonic metal-semiconductor heterostructures are widely studied for light-harvesting applications, yet the role of localized surface plasmon resonance (LSPR) in carrier extraction on the semiconductor side remains poorly understood. Here, we show that engineering the dielectric environment in Au/CeO2 using ultrathin nanoporous Ceria transforms plasmonically activated volume (PAV) on CeO2 side from interface-confined plasmonic excitation into a spatially extended, volume-activated process. meV-resolution electron energy-loss spectroscopy visualizes LSPR propagation throughout the porous framework, while photoluminescence spectroscopy reveals an enhanced contribution from fast charge-transfer channels. Quantitative analysis establishes the correlation among the PAV, fast charge transfer, and carrier utilization efficiency. These findings highlight the importance of semiconductor-side carrier dynamics in plasmonic heterostructures and establish dielectric-environment engineering as an effective strategy for extending plasmonic functionality beyond the immediate metal-semiconductor interface.