Metal Nanoshells for Enhanced Solar-to-Fuel Photocatalytic Conversion

In our preliminary study, we had prepared quaternary semiconductor powder of AgxInxZnyS2x+y, a photocatalysts with a high activity. In this study, we further extended the investigation, changed the amount of indium in a series of solid solutions, and increased the photochemical activity substantially. With little adjustment of the ratios of [In]/[Ag], the hydrogen production rate of the photocatalysts, AgxInyZnzS(x+3y+2z)/2, are significantly improved. The most enhancement of the activity can go up to four times, compared to our first generation photocatalyst. SEM images show that different amount of nonosteps on the surface relate to the ratios of [In]/[Ag]. These edges of nanosteps are considered as the active sites that facilitate the electron-hole separation, leading to higher solar-to-fuel conversion efficiency. The other ingredient, zinc, is used to control the band gap. Both changes of indium and zinc, we maximized the efficiency of this photocatalyst (970 μmol/h·g). In a separate experiment, the photocatalystic reactions were carried out at elevated temperature. The effect of temperature, typically with addition of Ag@Au NPs (nanoparticles) was evaluated. The presence of metal nanoshells can absorb the solar energy in the IR range. However, the broad absorption of metal nanoshells also covered the visible-light region, which decrease the efficiency of the metal sulfide photocatalysts. The incorporation of metal nanoshells, as well as the nanostructure of photocatalyst will be further investigated.