Oxysulfide photocatalyst for visible-light-driven overall water splitting

Oxysulfide semiconductors have narrow bandgaps suitable for water splitting under visible-light irradiation, because the electronegative sulfide ions negatively shift the valence band edges of the corresponding oxides 1 , 2 . However, the instability of sulfide ions during the water oxidation is a critical obstacle to simultaneous evolution of hydrogen and oxygen 3 . Here, we demonstrate the activation and stabilization of Y 2 Ti 2 O 5 S 2 , with a bandgap of 1.9 eV, as a photocatalyst for overall water splitting. On loading of IrO 2 and Rh/Cr 2 O 3 as oxygen and hydrogen evolution co-catalysts, respectively, and fine-tuning of the reaction conditions, simultaneous production of stoichiometric amounts of hydrogen and oxygen was achieved on Y 2 Ti 2 O 5 S 2 during a 20 h reaction. The discovery of the overall water splitting capabilities of Y 2 Ti 2 O 5 S 2 extends the range of promising materials for solar hydrogen production. The instability of sulfide ions during water oxidation prevents simultaneous evolution of hydrogen and oxygen. An oxysulfide semiconductor photocatalyst, Y 2 Ti 2 O 5 S 2 , is shown to evolve H 2 and O 2 via a water-splitting reaction under visible-light irradiation.