Hydrogen-reduced bismuth oxyiodide nanoflake arrays with plasmonic enhancements for efficient photoelectrochemical water reduction

Bismuth oxyiodide has attracted strong interest as a nano-engineered material for high-performance electrodes in photoelectrochemical (PEC) cells. Herein, we demonstrate the visible-light-sensitive PEC photocathodes based on nano-engineered bismuth oxyiodide (BiOI). The photocathodes are comprised of plasmonic Au nanoparticles (NPs) on hydrogen-reduced BiOI (H-BiOI) nanoflake arrays. The BiOI-based photocathodes exhibit an AM 1.5 photocurrent of 3.6 0.1 mA/cm at 0 V vs reversible hydrogen electrode. We attribute the enhanced photoreduction performance of our photocathodes to three factors that increase the formation and separation rates of electron-hole pairs for photocatalysis. Firstly, the small thickness of the nanoflakes facilitates the diffusion of minority carriers to the surfaces before their recombination. Secondly, the hydrogenation-induced oxygen vacancies in H-BiOI lead to increased acceptor density. Lastly, plasmonic effects in Au NPs enhance the light absorption, hot-carrier injection, and resonant energy transfer in the composite electrodes. Our experiments are coupled to optical simulations. This work demonstrates the tremendous potential of coupling plasmonic effects with nanoengineering to innovate visible-light-sensitive photocathodes for the realization of efficient PEC cells. ã 2016 Elsevier Ltd. All rights reserved.