Protonated layered perovskite oxides H1.9K0.3La0.5Bi0.1Ta2O7 (HKLBT) and H1.6K0.2La0.3Bi0.1Nb2O6.5 (HKLBN), which were prepared from K0.5La0.5Bi2M2O9(M = Ta; Nb)(KLBT(N)) by H ion-exchange in 3M HCl solution, were found as good photocatalysts for water splitting under UV light irradiation. The characterization by XRD, ICP and TG revealed that HKLBT(N) retained layered structure of their parent materials KLBT(N) after HCl treatment. An amount of exfoliation of Bi during the protonated process caused the decrease of contribution of Bi 6p in conduction band (CB) and thus resulted in more negative CB potential. HKLBT(N) showed considerable higher photocatalytic activity for H-2 and/or O-2 evolution than KLBT(N) in the absence of sacrificial reagents, which was attributed to the higher position of conduction band and the layered structure after acid treatment. It was concluded that the interlayer modification via ion-exchange for layered K0.5La0.5Bi2M2O9 (M = Ta; Nb) is a potential way to construct novel photocatalysts with high activity for water splitting. Copyright (c) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.