Photocatalytic hydrogen production from suspension of spinel powders AMn2O4(A = Cu and Zn)

Two narrow band gap-semiconductors AMn(2)O(4) (A=Cu and Zn) with p-type semiconductivity and crystallising in the spinel structure have been studied for photoassisted hydrogen production by visible light in aqueous solution containing sulfide S2- or sulfite SO32, The highest H-2 evolution rate, obtained under illumination with platinized Cu-oxide, was found to be 0.26 x 10(-2) ml mg(-1) h(-1) in a 0.1 M SO32- alkaline solution and does not depend on specific area. H-2 evolves over oxide whereas oxidation of S2- and/or SO32- occurs on platinum that behaves as a counter electrode. When sulfide is used as hole scavenger, the hydrogen production decreases over time and reaches a zero value after 3 h because of the formation of coloured polysulfides S-n(2-), which acts as an optical filter and compete with water reduction. (C) 2002 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.