THE PHOTOCATALYTIC PRODUCTION OF H-2 FROM MOLYBDENUM SULFUR-COMPOUNDSLOADED ON TIO2

The photocatalytic evolution of molecular hydrogen from aqueous suspen sions of colloidal TiO2 loaded with MoS42- and Mo2S4(S2C2H4)22- was st udied as a function of pH, loading and light intensity. The efficiency of these systems, in which polyvinyl alcohol and ethylenediamine tetr aacetic acid (EDTA) were utilized as sacrificial electron donors, was compared with the well-studied systems utilizing platinum as an electr on transfer catalyst. Optimum loading levels were 20 ions per particle for tetrathiomolybdate and 6 ions per particle for the thio dimer. Bo th of the Mo-S systems were only about 40% as efficient as platinum. Q uantum yields of molecular hydrogen approximately doubled as the inten sity was decreased by a factor of 10 and increased about twofold when the more efficient hole scavenger, EDTA, was added to the mixture. The highest yield obtained, in terms of the percentage utilization of the photoproduced electrons, was 11.5% compared with 28.2% for platinum. Except for differences in optimum loading levels, both catalysts gave similar results.