Lawrence Berkeley National Laboratory

In recent years, hybrid nanostructure consisted of plasmonic metals and different dielectrics have attracted much attention for their intriguing plasmonic properties. Recent studies have also shown that by introducing plasmonic metals, the photocatalytic efficiency of semiconductor can improve via plasmon-enhanced light absorption. In this work, we have demonstrated excellent photocatalytic properties for hydrogen production using hexagonal close-packed core-shell Au/TiO2 hybrid nanocrystal arrays. Under both ultra-violet and visible light, significant increase in the hydrogen production from methanol (20%) solution splitting was achieved with the hybrid Au/TiO2 nanocrystal arrays in comparison with bare TiO2 thin film as well as randomly distributed Au/TiO2 nanocrystals. From the finite difference time domain (FDTD) simulation, the significant increase (up to 60%) in hydrogen production can be correlated to strong and optimum coupling of the enhanced electric field from localized surface plasmon resonance in Au/TiO2 nanocrystal arrays. In addition to allowing more accurate measurement of plasmonic enhancement, the ordered nanostructures have been shown to be especially amenable to the systematic analysis of lateral coupling of plasmonically enhanced electric field. As a result, optimal structures with appropriate spacing of core-shell metal-dielectric nanocrystals, metal core size and dielectric shell thickness for maximum enhancement can be designed.