Solar to chemical energy conversion using titania nanorod photoanodes augmented by size distribution of plasmonic Au-nanoparticle

Abstract

Amid a substantial development of plasmonic noble metal sensitized TiO2 nanostructure based photoanodes used in solar to chemical energy conversions, two key considerations to further enhance the broad spectrum photocurrent are the reduction in the recombination of photogenerated charge carriers at the interface and an amplification of local electric field near the interface to promote the surface plasmon resonance mediated hot electron injection. We present in this article the enhanced photo-activity of sputtered Au nanoparticles (Au-NPs) of different size distribution attached to the hydrothermally grown TiO2 nanorod (TiO2-NRs) arrays which well addresses the above two considerations. A six fold increase in the device photocurrent is complemented by a homogeneous distribution of Au-NP centered at 15 nm led hot electron transfer into the titania conduction band. The present combination of the TiO2-NRs and size distributed Au-NP exhibits a charge transfer resistance as low as 1.5 kΩ as compared to 5kΩ in unsensitised electrode which results in a reduced exciton recombination and local field enhancement as confirmed by finite difference time domain based simulation. The enhanced solar water splitting capability is also demonstrated.