Multiplasmon modes for enhancing photocatalytic activity of Au/Ag/Cu2O core-shell nanorods

One of critical challenges for semiconductor photocatalysis is high efficiency utilization of solar energy. For plasmonic metal-semiconductor photocatalysts, the photocatalytic activity over an extended wavelength range for the photoresponsive semicondcutor could be significantly improved either via the direct electron transfer (DET) or via the plasmon-induced resonant energy transfer (PIRET). Still, the narrow spectral overlap of plasmon and semiconductor band edge is a key factor in restricting the development of PIRET. Herein, we have introduced a simple and versatile strategy to realize broad spectral overlap by creating multipolar plasmon resonances near semiconductor band edge. Cu2O coated Au/Ag nanorods (NRs) were prepared using a facile wet chemistry method. Transverse plasmon modes of Au/Ag/Cu2O NR can split into a dipole and an octupole plasmon modes. The core aspect ratio and shell thickness could be used to regulate these two modes for extending the spectral overlap of plasmon resonance and Cu2O band edge. Au/Ag/Cu2O NRs were found to display enhanced visible light photocatalytic activity compared to spherical Ag/Cu2O nanoparticles. The enhancement mechanism was ascribed to both dipole and octupole plasmon modes boosting electron-hole separation in Cu2O via PIRET as confirmed by transient absorption measurements.