Abstract: The four-component system composed of zinc tetraphenylporphyrin as photosensitizer, various viologen derivatives as electron mediator, ethylene diaminetetracetic acid disodium salt as electron donor and platinum as catalyst has been investigated. It was found that hydrogen evolution depended on the viologens used, the longer the aliphatic group (Gn V²⁺) in viologens, the less the hydrogen evolution. The amount of hydrogen evolution was too small to detect until viologens n>8. The hightest hydrogen evolution was obtained while CTAB and methyl viologen (C1 V²⁺) were used.

Key words: photodecomposition, photosonsitizers, surfactants, viologens, zinctetraphenyl-porphyrin