Photoelectrochemical hydrogen production from water using p-type and n-type oxide semiconductor electrodes

► Photoelectrochemical hydrogen and oxygen production from water without external applied voltage. ► CaFe2O4/Ca2Fe2O5 and TiO2 electrode system. ► The open-circuit voltage was 1.09 V. ► The short-circuit current was 550 μA/cm2. ► The ratio of hydrogen/oxygen evolved was around 3.7.