Light-Driven Water Splitting Mediated by Photogenerated Bromine

摘要

Light-driven water splitting was achieved using a dye-sensitized mesoporous oxide film and the oxidation of bromide (Br-) to bromine (Br-2) or tribromide (Br-3(-)). The chemical oxidant (Br-2 or Br-3(-)) 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)(2)], (1; pic=picoline, bda=2,2-bipyridine-6,6-dicarboxylate). The photochemical oxidation of bromide produces a chemical oxidant with a potential of 1.09V vs. NHE for the Br-2/Br- couple or 1.05V vs. NHE for the Br-3(-)/Br- couple, which is sufficient to drive water oxidation at 1 (Ru-V/IV approximate to 1.0V vs. NHE at pH5.6). At pH5.6, using a 0.2m acetate buffer containing 40mm LiBr and the [Ru(4,4-PO3H2-bpy)(bpy)(2)](2+) (RuP2+, bpy=2,2-bipyridine) chromophore dye on a SnO2/TiO2 core-shell electrode resulted in a photocurrent density of around 1.2mAcm(-2) under approximately 1 Sun illumination and a Faradaic efficiency upon addition of 1 of 77% for oxygen evolution.