H2 production by the water splitting reaction using photocatalysts derived from calcined ZnAl LDH

Photocatalysts based on calcined ZnAl layered double hydroxides were obtained by coprecipitation and the subsequent thermal treatments at different temperatures. The calcined materials were characterized and its photocatalytic behavior was evaluated in the water splitting reaction in presence of UV irradiation. According to the XRD analysis, there was detected the presence of Zn as hexagonal ZnO in all the samples, as well as Al forming ZnAl2O4 and Zn6Al2O9, depending on the temperature of calcination employed. H-2 yield was higher as the annealing temperature was increased due to the formation of the heterojunctions of ZnO with the Zn6Al2O9 and ZnAl2O4 oxides, reaching the maximum value in the sample annealed at 600 degrees C. Some decay in the activity was observed in the sample calcined at 700 degrees C, probably due to the higher recombination rate of the photo-generated charge carriers in that heterojunction in comparison with that obtained at 600 degrees C.