Three-dimensional plasmonic photoanode of Co3O4 nanosheets coated onto TiO2 nanorod arrays for visible-light-driven water splitting

In this work, we report for the first time a plasmonic photoanode by decorating Au nanoparticles (NPs) onto two-dimensional (2D) Co3O4 nanosheets (NSs)/one-dimensional (1D) TiO2 nanorod arrays (NRAs) (Au/Co3O4/TiO2-NRAs) for enhanced visible-light photo-electrochemical (PEC) water splitting. In this plasmonic photoanode, TiO2 NRAs act as an electron acceptor, plasmonic Au NPs and hierarchical Co3O4 NSs serve as visible-light harvesters. Light absorption shows that Au/Co3O4/TiO2-NRAs heterojunction architectures exhibit greatly improved ability to harvest visible light due to the surface plasmon resonance (SPR) absorption of Au NPs and visible light harvesting ability of Co3O4 NSs. Spectroscopic measurements demonstrate that a type II band alignment is formed between Co3O4 and TiO2. Benefiting from the SPR effect, type II band alignment and novel hierarchical architecture, plasmonic Au/Co3O4/TiO2-NRAs photoanode shows remarkably enhanced visible-light PEC water splitting activity compared with Co3O4/TiO2-NRAs and pristine TiO2-NRAs photoanodes. Photocurrent density achieved by plasmonic photoanode is 37 and 1.2 times higher than those of TiO2-NRAs and Co3O4/TiO2-NRAs photoanodes, respectively. This work provides a promising strategy to highly enhance visible-light PEC water splitting activity of wide band-gap semiconductor-based photoelectrode materials. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.