Plasmonic Ag@TiO2 Core-Shell Nanoparticles for Enhanced CO2 Photoconversion to CH4

Ag@TiO2 nanoparticles (NPs) with Ag metal cores and TiO2 semiconductor shells were prepared with a hydrothermal method and their structure was characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The core-shell Ag-TiO2 NPs were deposited on a glass plate and employed as photocatalysts for CO2 conversion by irradiation of solar simulator (AM1.5) under CO2 atmosphere. Selective CH4 evolution by CO2 photoconversion was attained with the core-shell Ag@TiO2 NP photocatalyst. The CH4 evolution rate normalized by specific surface areas was ten times higher than those of reference TiO2 NPs and conventional TiO2 NPs with accompanying Ag deposits. The role of the Ag core was also demonstrated in photodecomposition of a dye by the core-shell Ag@TiO2 NPs. These results suggested the high photocatalytic activity of the core-shell Ag@TiO2 NPs was archived due to bandgap improvement of the TiO2 shell and increase of photon flux to the TiO2 shell by the plasmonic Ag core.