Suppression of Charge Recombination by Growth of a TiO

Hematite (α-Fe2O3) represents a photoelectrode material that holds high potential to realize efficient and stable photoelectrochemical (PEC) hydrogen production due to its narrow bandgap for efficient solar absorption and good stability in alkaline electrolytes. However, pure α-Fe2O3 has been plagued by its poor conductivity with low carrier mobility and rapid charge recombination, which greatly hinder its photoelectrochemical applications. Herein, a hybrid photoanode is rationally designed by growing an amorphous TiOx overlayer on a Ti-doped α-Fe2O3 nanorod photoanode to passivate surface states for improved PEC performance. Consequently, the photocurrent achieved by the composite photoanode (Ti-Fe2O3/TiOx) is around 1.24 mA·cm-2 at 1.23 V vs RHE, up to about 1.7 and 62.0 times that of Ti-doped Fe2O3 (0.74 mA·cm-2) and untreated α-Fe2O3 (0.02 mA·cm-2) photaonodes, respectively. The intensive study of charge dynamics reveals that the improved PEC response of the composite photoelectrode can be ascribed to the Ti doping and TiOx passivation effect greatly suppressing the charge recombination kinetics constant (krec) and promoting the charge transfer efficiency (ηtran), which resulted in accelerated charge separation and enhanced PEC activity. This work emerges as a feasible approach to designing the Fe2O3-based photoelectrode for enhanced solar water oxidation activity.