Influence of sacrificial agent on Cu photodeposition over TiO2/MCH composites for photocatalytic hydrogen production

Abstract

Titanium (ca. 11 wt%) was dispersed on a carbonaceous mesoporous support and modified with copper (ca. 5 wt%) photodeposited using either glycerol or methanol as the sacrificial agent ((Cu-TiO2/MCH_(Gly) and Cu-TiO2/MCH_(Met) solids, respectively). In the former case, copper particles were more preferentially deposited on titania and copper nanoaggregates were more abundant than in the latter. The synthesized catalysts were tested in the glycerol photoreforming reaction and it was found that there was an increase in activity on copper photodeposition as compared to titania-mesoporous carbon composite, being higher in Cu-TiO2/MCH_(Gly) than in Cu-TiO2/MCH_(Met) (5 and 4 times, respectively). Nevertheless, copper present in Cu-TiO2/MCH_(Gly) redisperses as reaction proceeds, the catalyst exhibiting a more similar activity to Cu-TiO2/MCH_(Met) after one use. An additional reason for catalyst deactivation is strong adsorption of reaction intermediates. In this sense, competitive reactions with glycolic and glyceric acid (two of the intermediates identified by HPLC-DAD/RID) and glycerol gave some hints on reaction mechanism which could also be helpful for future identification of the species responsible for the catalysts deactivation.