Tiny Au nanoparticles mediation strategy for preparation of NIR CuInS2 QDs based 1D TiO2 hybrid photoelectrode with enhanced photocatalytic activity

Abstract

Copper indium sulfide (CuInS2) is attracting growing attention as a green, photo-absorption material; yet CuInS2 alone displays poor photocatalytic activity owing to the severe charge carrier recombination resulting from its high defect tolerability — especially for quantum dots (QDs) with the high volume-to-surface ratio. In an attempt to mitigate this issue, a ternary type II heterostructure hybrid photoelectrode was successfully prepared through in situ photoreduction deposition of tiny Au nanoparticles (NPs) onto free-standing TiO2/Ti nanowire arrays (NWAs) loaded with near-infrared (NIR) CuInS2 QDs. This configuration permits CuInS2 QDs to act as a photosensitizer with a light harvest region extending 800 nm, while tiny Au NPs function as photocatalytic reaction initiators to enhance organic molecule decomposition. Most importantly, using TiO2/Ti NWAs as the supporting substrate not only provides considerably more sites for highly loaded and dispersed catalysts, but also reserves one dimension space for ions, mass diffusion, and photo-generation charge carrier transport. As expected, the results showed that incorporation of Au NPs (CuInS2/Au/TiO2 NWAs) increased photocurrent intensity by 65.2% compared with CuInS2/TiO2 NWAs. What's more, the phenol degradation efficiency was 94.3% after 180 min of light irradiation, which is significantly higher than that of other control photoelectrodes. Finally, the superior performance also benefits from the intimate contact interface between different components created through our proposed strategy. A photoluminescence (PL) technique, using terephthalic acid (TA) as the probe molecule, confirmed that a highly reactive hydroxyl radical based photocatalytic mechanism is also responsible for such significant photocatalytic efficiency.