On electron loss lowering at hematite photoelectrode interfaces

Photoelectrodes nanoscale interface design has become a key factor to enhancing their photoelectrochemical performance for water splitting by reducing the photogenerated charge recombination, thus ensuring their efficient separation, transport, and collection. In this work, hematite (α-Fe₂O₃) photoanodes were prepared from a simple and scalable methodology capable of synergistically mitigating the charge loss and recombination at all interfaces (i.e., fluorine-doped tin oxide/hematite, hematite/hematite, and hematite/electrolyte) and achieving overall efficiency of ∼50% for the water oxidation reaction compared to pristine photoelectrodes. The external quantum efficiency at 1.23 V versus reversible hydrogen electrode of pristine hematite was enhanced 6.7 times with the modifications of the three interfaces (Al₂O₃/NbH/NiFeO_x). Electrochemical impedance spectroscopy and intensity-modulated photocurrent spectroscopies were applied to probe and monitor the photogenerated charge carrier dynamics revealing a substantial improvement in charge separation and collection at the back-contact interface as well as a partial mitigation of the surface states at the hematite–electrolyte interface.