The Z-scheme of water splitting is comprised of H(2)-photocatalyst and O(2)-photocatalyst with aid of electron transfer mediator to produce hydrogen and oxygen, respectively. A twin reactor, which divided H(2)-photocatalyst and O(2)-photocatalyst in two compartments using a membrane, can separate H(2) and O(2) thus preventing backward reaction. Pt/SrTiO(3):Rh and BiVO(4) were used as the H(2)-photocatalyst and the O(2)-photocatalyst, respectively. The diffusion of electron mediator, Fe(2+)/Fe(3+), through Nafion membrane was investigated. The transfer rate of mediator ions was remarkably larger than the photoreaction rate, indicating that membrane did not delay the water-splitting reaction in the twin reactor. Under the favorable condition, the hydrogen generation rate reached 0.65 mu mol/gh and matched the H(2)/O(2)stoichiometric ratio of water splitting. We found that the generation of H(2)in the twin-reactor system was the rate-limiting step of the water-splitting reaction. By using the twin reactor, the deactivation of Pt/SrTiO(3):Rh could be minimized due to the suppression of Fe(OH)(3)formation on the photocatalyst surface. (C) 2011 Elsevier B.V. All rights reserved.