(722f) TiO2/Au Nanocomposites for Photocatalytic Water Splitting: Understanding the Mechanisms By Which Au Impacts Activity

We aim to understand the mechanisms by which Au impacts the water-splitting activity of TiO2.  Although TiO2 is one of the most widely studied materials for photocatalytic water splitting, it has two major drawbacks— slow oxygen evolution kinetics and the inability to absorb visible light.  The addition of Au to TiO2 may create a composite catalyst with increased activity compared to TiO2 alone.  This is because Au has strong absorbance in the visible range from localized surface plasmon resonance (LSPR).  Recent studies have shown that LSPR can spatially localize the creation of electron holes as well as impart visible-light activity when paired with a photocatalyst that is unable to absorb visible light. By spatially localizing the creation of holes, the Au may facilitate the oxygen evolution reaction by increasing the chances that an adsorbate encounters a hole and proceeds down the reaction pathway.  To investigate which effects derive from LSPR and which are catalytic effects of the Au, we run the water-splitting reaction under different light conditions (UV-only, visible-only, and UV-visible).  Since Au only exhibits LSPR in the visible region, we determine the effect that adding Au nanoparticles has on TiO2’s absorbance and kinetics resulting from both LSPR and non-LSPR mechanisms.