To explore a more function-stable and energy-efficient bipolar membrane, palygorskite and FeCl3 were added at the intermediate layer as water-splitting catalysts. As proven, the two materials have a synergetic effect on water splitting. Particularly, the bipolar membrane modified with 5 g dm(-3) palygorskite and 0.005 mol dm-3 FeCl3 can achieve a voltage drop of 0.68V at 100 mA cm(-2) and loses only 14.7 mu g of Fe after an electrodialysis operation at 100 mA cm(-2) for 660 min. Obviously, palygorskite can protect ferric ions from significant loss, which makes the membrane stable in the performance of water splitting. Nevertheless, how palygorskite immobilizes ferric ions is still under investigation. (c) 2008 Elsevier B.V. All rights reserved.