Amorphous FeO x Overlayer Coupled with Co3O4 Nanoparticles Passivating Hematite Photoanodes for Water Oxidation

Hematite is a significant material for photoanodes incatalyticwater oxidation. Modification overlayers play an important role inimproving the activity of the hematite photoanode, which suffers seriousrecombination by inevitable surface defects. Herein, a thin amorphousFeO( x ) overlayer was spin-coated on Fe2O3 nanorods. The photoanode reached a 1.7-foldincrease in current density, and the modification improved the injectionefficiency principally. A more effective functional overlayer wasconstructed by subsequently depositing Co3O4 nanoparticles, which achieved a higher photocurrent of 1.39 mA cm(-2) at 1.23 V-RHE and a cathodic 80 mV shiftof the onset potential. Based on electrochemical and charge kineticscharacterization, the FeO x overlayer isfound to passivate the surface traps, favoring charge transfer throughthe electrode-electrolyte interface, thus reducing the recombination.With the aid of the p-n heterojunction between Co3O4 and Fe2O3 and the strengthenedpassivation effect, the reaction kinetics was further enhanced bythe deposition of Co3O4. The facile fabricationof the FeO x overlayer and the applicationof synergetic overlayers for hematite photoanodes consisting of passivationlayers or multiple cocatalysts are inspiring and promising for futuremodification research.