Photoinduced hydrogen evolution by use of porphyrin, EDTA, viologens and hydrogenase in solutions and Langmuir–Blodgett films

Photoinduced hydrogen evolution was investigated by use of a zinc porphyrin, EDTA, viologens and hydrogenase (H2ase) in the solutions and Langmuir–Blodgett (LB) films. An almost linear increase of hydrogen evolution rate was observed with the increase of H2ase concentrations from 1 to 5 μg/ml. For the zinc porphyrin, EDTA and methyl viologen, when their concentrations increased to a given value, hydrogen evolution did not show obvious increase. Phospholipid-porphyrin mixed LB films were prepared and used as photosensitizer for the photoinduced hydrogen evolution. Spectroscopic studies of the deoxygenated solutions indicated a “new” absorption band (in the solutions) or sharp peaks (in the LB films) when the sample solutions were irradiated, which was ascribed to the formation of an excited complex of porphyrin–EDTA (or -EDTA breakdown products). This excited complex was unstable to air.