Light-Driven Water Splitting Mediated by Photogenerated Bromine.

Light-driven water splitting was achieved using a dye-sensitized mesoporous oxide film and the oxidation of bromide (Br ) to bromine (Br ) or tribromide (Br ). The chemical oxidant (Br or Br ) is formed during illumination at the photoanode and used as a sacrificial oxidant to drive a water oxidation catalyst (WOC), here demonstrated using [Ru(bda)(pic) ], (1; pic=picoline, bda=2,2'-bipyridine-6,6'-dicarboxylate). The photochemical oxidation of bromide produces a chemical oxidant with a potential of 1.09 V vs. NHE for the Br /Br couple or 1.05 V vs. NHE for the Br /Br couple, which is sufficient to drive water oxidation at 1 (Ru ≈1.0 V vs. NHE at pH 5.6). At pH 5.6, using a 0.2 m acetate buffer containing 40 mm LiBr and the [Ru(4,4'-PO H -bpy)(bpy) ] (RuP , bpy=2,2'-bipyridine) chromophore dye on a SnO /TiO core-shell electrode resulted in a photocurrent density of around 1.2 mA cm under approximately 1 Sun illumination and a Faradaic efficiency upon addition of 1 of 77 % for oxygen evolution.