In an effort to facilitate water photosplitting at surfaces, we identify quantum well states of magic gold clusters supported on ultrathin MgO/Ag(001) as the key to favor sunlight absorption and photocatalytic reactions. Based on density functional theory (DFT) and time-dependent DFT calculations, the adsorption geometry, electronic structures, and excited state properties of supported metal nanoparticles can be precisely controlled. By decreasing the thickness of MgO film, charge transfer to supported gold clusters, and therefore the occupation and energy spacings of quantum well states, can be gradually tuned, leading to redshifted and enhanced plasmonic excitations and optimized energy levels for water splitting.

• Received 15 May 2012

DOI:https://doi.org/10.1103/PhysRevB.86.045455