Photolytic degradation of aqueous hydrogen sulphide with simultaneous hydrogen production using visible light

Abstract

Hydrogen was photochemically produced from an aqueous, catalyst-free solution containing Ru(bipy), methyl viologen, and hydrogen sulphide as electron donor. This system was most efficient at pH 5 after 4 h irridiation, but the extrapolated turnover number was higher at a somewhat higher pH because of the sensitizer bleached substantially as a function of pH, most serious at low pH. The behaviour of the methyl viologen radical is different to that in similar systems but with EDTA instead of H 2S as electron donor. In systems with EDTA, the methyl viologen radical forms a CT-complex with a proton with p K a = 4.0 whereas with hydrogen sulphide, competing reactions reduce the formation of methyl viologen radicals at pH > 4. Nevertheless, with H 2S three orders of magnitude more hydrogen was produced than with EDTA in catalyst-free solutions.