From doping to composites: zirconia (ZrO₂) modified hematite photoanodes for water splitting

Herein, a ZrO₂ added α-Fe₂O₃ photoanode that can split water at low applied potential is reported. First, the pristine hematite α-Fe₂O₃ photoanode was synthesized using an aerosol-assisted chemical vapour deposition (AACVD) method followed by modification with various amounts of ZrO₂ (2 to 40%) in the form of thin films on conducting glass substrate. The XRD, Raman spectroscopy and scanning electron microscopy (SEM) analyses confirmed the presence of the monoclinic phase of ZrO₂ in the composites with multifaceted particles of compact morphology. The optical analysis showed an increase in the absorbance and variation in band gap of the composites ascribed to the heterogeneity of the material. The photoelectrochemical studies gave a photocurrent density of 1.23 mA cm^-2 at 1.23 V vs. RHE for the pristine hematite and remarkably higher value of 3.06 mA cm^-2 for the optimized amount of ZrO₂ in the modified α-Fe₂O₃ photoanode. To the best of our knowledge, this is the highest photocurrent reported for a ZrO₂ containing photoanode. The optimized composite electrode produced nine times more oxygen than that produced by pristine hematite.