Plasmonic Black Absorbers for Enhanced Photocurrent of Visible-Light Photocatalysis

<p> Plasmonic resonance of noble metal nanoparticles can drastically enhance the visible response of wide-bandgap photocatalysts such as TiO2, but the current technology has two fundamental problems: narrow absorption band and low absorption, which limit the energy efficiency of photocatalysis using sunlight. Here, an original plasmonic black absorber is reported, which sandwiches a 150 nm TiO2 layer between a layer of random Au nanoparticles and a rough Au surface (200 nm thick). The combined plasmonic effect of the Au nanoparticles and the Au rough surface enables a strong absorption (72%-91%) over 400-900 nm and a significantly (20-fold) enhanced photocurrent as compared to the bare TiO2 film. The strong absorption to visible and near infrared light, and the much enhanced photocurrent make the black absorber an ideal material for solar applications such as photocatalytic, photosynthetic, photovoltaic, and photothermal systems.