Solar Photocatalytic Hydrogen Production from Water Using a Dual Bed Photosystem

We have been investigating the use of organic pigments as semiconductor photocatalysts in a dual stage water decomposition scheme that would ultimately use solar energy to generate hydrogen from water. We have shown that by employing a combination of simple screening procedures on prospective compounds, such as semiempirical molecular orbital calculations and thin film voltammetry, we can quickly determine whether a compound will be capable of O2 or H2 evolution. A number of fused heteroaromatic compounds were identified as possible photocatalysts for O2 evolution; we subsequently verified that various perylene, indanthrone, and quinacridone compounds do indeed evolve O2 under Xe lamp illumination. A number of phthalocyanine compounds were shown to evolve H2. Using a perylene diimide derivative as the O2-evolving photocatalyst and copper phthalocyanine as the H2-evolving photocatalyst, respective oxidative and reductive water decomposition was observed using the same IO3 /I redox electrolyte, demonstrating that continuous closed cycle dual bed photocatalytic water-splitting is feasible.