Unbiased Photoelectrochemical Solar Hydrogen Generation on Highly Stable, Ultrathin Organic Linker/Metal Ions-Treated InGaN Nanorods on Metal

Thursday, 5 October 2017: 11:00
National Harbor 6 (Gaylord National Resort and Convention Center)
M. Ebaid, D. Priante, G. Liu (King Abdullah University of Science and Technology), C. Zhao (King Abdullah University of Science & Technology), M. S. Alias, U. Buttner, T. K. Ng (King Abdullah University of Science and Technology), T. T. Isimjan (Saudi Arabia Basic Industries Corporation), H. Idriss (UCL (UK)), and B. S. Ooi (King Abdullah University of Science and Technology)
InGaN-based nanostructures have recently been recognized as promising materials for efficient solar hydrogen generation. This is due to their chemical stability, adjustable optoelectronic properties, suitable band edge alignment, and large surface-to-volume ratio. The inherent high density of surface trapping states and the lack of compatible conductive substrates, however, hindered their use as stable photo-catalysts. We have designed, synthesized and tested an efficient photocatalytic system using stable InGaN-based nanorods (NRs) grown on an all-metal stack substrate (Ti-Mo) for a better electron transfer process. In addition, we have applied a bifunctional ultrathin thiol-based organic surface treatment using 1,2-ethanedithiol (EDT), in which sulfur atoms protected the surface from oxidation. This treatment has dual functions, it passivates the surface (by the removal of dangling bonds) and creates ligands for linking Ir-metal ions as oxygen evolution centers on top of the semiconductor. This treatment when applied to InGaN NRs resulted in a photo-catalyst that achieved 3.5% solar-to-hydrogen (STH) efficiency, in pure water (pH~7, buffer solution) under simulated one-sun (AM1.5G) illumination and without electrical bias. Over the tested period, a steady increase of the gas evolution rate was observed from which a turnover frequency of 0.23 s-1 was calculated. The novel growth of InGaN-based NRs on a metal as well as the versatile surface functionalization techniques (EDT-Ir) have a high potential for making stable photo-catalysts with adjustable band gaps and band edges to harvest sun light.