Enhanced photoelectrochemical water splitting efficiency of hematite (α-Fe2O3)-Based photoelectrode by the introduction of maghemite (γ-Fe2O3) nanoparticles

To enhance the photo-electrochemical performance of hematite photo-electrode, we designed a phase-junction configuration of α and γ-Fe2O3. By inserting maghemite (γ-Fe2O3) particles synthesized by reverse micelle deposition, which is for suppressing the phase transition from γ-Fe2O3 to α-Fe2O3, in between a hematite (α-Fe2O3) layer and fluorine-doped tin oxide (FTO) substrate, we could achieve a drastic improvement of the current density. We successfully confirmed using Raman spectroscopy that γ-Fe2O3 still remained after the annealing process performed at high temperature and the phase-junction configuration of α/γ-Fe2O3 was constructed. In addition, we could demonstrate using a time-resolved spectroscopic method and an electro-impedance spectroscopy measurement that the enhancement of the performance originated from the retardation of the recombination, resulting from the improvement of the charge separation efficiency.