Crystalline Fe2O3/Fe2TiO5 heterojunction nanorods with efficient charge separation and hole injection as photoanode for solar water oxidation

Abstract We have constructed a Fe 2 O 3 /Fe 2 TiO 5 heterojunction based photoanode deposited on Fluorine Doped Tin Oxide (FTO) substrate by initially fabricating hematite (Fe 2 O 3 ) nanorods and subsequently pseudobrookite (Fe 2 TiO 5 ) nanoporous thin film on top of them. Comparatively lower annealing temperature of 650 °C (usually 750 °C or above) was used to avoid degradation of FTO. The crystalline Fe 2 O 3 /Fe 2 TiO 5 heterojunction shows a considerable enhancement in photocurrent density ca. 1.4 mA/cm 2 and high surface charge separation efficiency of 85% at operating voltage of 1.23 V vs RHE as compared to its constituents. The crystalline heterojunction showed overall improvement in performance due to enhanced charge separation owing to the favorable band alignment with Fe 2 O 3 nanorods and efficient injection of photogenerated holes through surface states into the electrolyte observed through Electrochemical Impedance Spectroscopy.