Z-scheme systems for water splitting were successfully developed by employing Rh- and Ir-doped metal oxides with SrTiO3:Rh and BiVO4 photocatalysts.

The photocatalytic water‐splitting system ideally consists of just photocatalyst powder and water without any additives. Herein, improvement of water‐splitting activity under neutral conditions is achieved by applying Mo‐doping and cocatalyst‐loading to BiVO4 of an O2‐evolving photocatalyst in a Z‐scheme system with Ru‐loaded SrTiO3 doped with Rh as a H2‐evolving photocatalyst and a reduced graphene oxide as an electron mediator. The strategies are based on the idea that the Z‐schematic electron migration process in the powdered Z‐scheme system with reduced graphene oxide is similar to that in the photoelectrochemical system. Although the reaction condition becomes out of the ideal states, adding Ca(NO3)2 and CaCl2 into the reactant solution further improves the water‐splitting activity due to the formation of aggregated photocatalyst particles to boost the electron transfer from Mo‐doped BiVO4 to Ru‐loaded SrTiO3 doped with Rh through the reduced graphene oxide.

H2 and O2 gases are generated from water under visible light irradiation over cocatalysts loaded on different powdered photocatalysts in a Z‐scheme system. Reduced graphene oxide (RGO) sheets help the Z‐schematic electron transfer from O2‐evolving photocatalysts to H2‐evolving photocatalysts. More details can be found in article number http://doi.wiley.com/10.1002/ente.1900358 by Akihide Iwase, Akihiko Kudo, and co‐workers.