Effect of layer charge modification for Co-A1 layered double hydroxides: study by X-ray absorption spectroscopy

When tuning the exchange capacity of a Co2+, Al3+ containing layered double hydroxyde's (LDH's) material, a concomitant phenomenon of oxidation-migrat ion of the cations is observed for one of the end members. X-ray absorption spectroscopy, performed at the cobalt and aluminum k-edge, shows that part of the Co2+ cations are oxidized to Co3+, while Al3+ cations have left the LDH's layers, leading to a [Cox2+Co3+] intralayer composition. Interlamell ar AlO6 polyhedra are present after repetitive washing and exchange reactio ns, suggesting strong interactions with the LDH's layers. (C) 2001 Editions scientifiques et medicales Elsevier SAS. All rights reserved.