Photosensitized production of hydrogen by water-soluble tetraphenanthroporphyrazine in micellar solutions

The use of water soluble H2TPPSO3Na as a photosensitizer for the photoreduction of methyl viologen in micellar solutions at pH = 5 and pH = 6, has been investigated. The dye collects a large fraction of solar energy in the spectral region (330–730 nm). Illumination of solutions consisting of EDTA/MV2+/H2TTPSO3Na/Cetyl trimethyl ammonium chloride (CTAC) at pH = 5 and pH = 6 with visible light of different wavelengths, gave at (395 nm) and at (602 nm) an action spectrum of methyl viologen radical (MV+), similar to the absorption spectrum of the dye itself. No photosensitization was observed in the absence of cationic micelles. Irradiation of micellar solutions with visible light gave rise to a build up of methyl viologen radical, and in the presence of colloidial platinum in the system at pH = 6, led to hydrogen evolution. As the pH was lowered to 5 the quantity of hydrogen evolved was also lowered. For this process the quantum yield was very low compared to processes involving porphyrins, but there are indications that a more finely divided platinum may result in improved yields.