Observation of Charge Separation Enhancement in Plasmonic Photocatalysts under Coupling Conditions.

ABSTRACT

Surface plasmon resonance-induced charge separation plays key roles in plasmon-related applications, especially in photocatalysis and photovoltaics. Plasmon coupling nanostructures exhibit extraordinary behaviors in hybrid states, phonon scattering, and ultrafast plasmon dephasing, but plasmon-induced charge separation in these materials remains unknown. Here, we design Schottky-free Au nanoparticle (NP)/NiO/Au nanoparticles-on-a-mirror plasmonic photocatalysts to support plasmon-induced interfacial hole transfer, evidenced by surface photovoltage microscopy at the single-particle level. In particular, we observe a nonlinear increase in charge density and photocatalytic performance with an increase in excitation intensity in plasmonic photocatalysts containing hot spots as a result of varying the geometry. Such charge separation increased the internal quantum efficiency by 14 times at 600 nm in catalytic reactions as compared to that of the Au NP/NiO without a coupling effect. These observations provide an improved understanding of charge transfer management and utilization by geometric engineering and interface electronic structure for plasmonic photocatalysis.