VISIBLE-LIGHT PHOTOLYSIS OF HYDROGEN IODIDE USING SENSITIZED LAYERED SEMICONDUCTOR PARTICLES

Surface sensitization of internally platinized layered oxide semiconductor K4-xHxNb6O17.nH2O (x almost-equal-to 2.5), H2Ti3O7, and HTiNbO5 by RuL3(2+) (L = 4,4'-dicarboxy-2,2'-bipyridine) yields photocatalysts for the production of H-2 and I3- in aqueous iodide solutions. Flash photolysis experiments show that, at pH 3.0, excited-state RuL3(2+) injects an electron into K4-xHxNb6O17.nH2O and is rapidly re-reduced by I-. Steady-state photolysis at 450 nm in 50 mM aqueous KI (pH 3.0) yields H-2 and I3- in stoichiometric amounts, with an initial quantum yield of 0.3%. While H-2 and I3-, once formed, do not recombine at an observable rate, the rate of hydrogen evolution decreases as the concentration of I3- increases in the solution.