Novel twin reactor for separate evolution of hydrogen and oxygen in photocatalytic water splitting

Photocatalytic water splitting with separate H2 and O2 evolution is crucial because it eliminates the explosion potential and hydrogen-purification cost. A novel twin reactor was designed to separate the evolution of hydrogen and oxygen in photocatalytic water splitting under visible light. A modified Nafion membrane was employed to segregate the two photocatalysts in the twin reactor so that hydrogen and oxygen can be evolved separately. Conventional Z-scheme catalysts, Pt/SrTiO3:Rh and WO3, were used as hydrogen-photocatalyst and oxygen-photocatalyst, respectively. Fe2+ and Fe3+ were added in the reaction solution as electron-transfer mediator. The ratio of evolved H2 and O2 was in agreement with the stoichiometric ratio (2:1) of hydrogen and oxygen of water. An average hydrogen generation rate of 1.59 μmol/g-h was achieved in the twin-reactor system, which was twice as much as that in the conventional Z-scheme system. The improved H2 yield was due to the prevention of the water-splitting backward reaction in the twin reactor.