Temperature dependence for the reduction of water to hydrogen by reduced methyl viologen on platinum

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Abstract
The electron-transfer reactions from methyl viologen monocation radicals to colloidal platinum hydrosols were studied using the pulse-radiolysis technique. Besides the reduction of water, hydrogenation of methyl viologen on platinum also takes place in these reactions. Evolution of hydrogen is enhanced at higher temperatures (65 °C) and reduction of MV+ is hindered. The reaction shows complex behaviour in the presence of hydrogen because of the formation of reduction products which decrease the catalytic activity of platinum. The reaction rate decreases from 1.3 × 103 s–1 in an argon-saturated solution to 0.6 s–1 in a hydrogen-saturated solution in the presence of 2.5 × 10–5 mol dm–3 Pt hydrosols.