Boosting Hole Transfer in the Fluorine-Doped Hematite Photoanode by Depositing Ultrathin Amorphous FeOOH/CoOOH Cocatalysts

The charge transfer is a key issue in the development of efficient photoelectrodes. Here, we report a method using F-doping and dual-layer ultrathin amorphous FeOOH/CoOOH cocatalysts coupling to enable the inactive alpha-Fe2O3 photoanode to become highly vibrant for the oxygen evolution reaction (OER). Fluorine doping is revealed to increase the charge density and improve the conductivity of alpha-Fe2O3 for rapid charge transfer. Furthermore, ultrathin FeOOH was deposited on F-Fe2O3 to extract photogenerated holes and passivate the surface states for accelerated charge carrier transfer. Moreover, CoOOH as an excellent cocatalyst was coated onto FeOOH/F-Fe2O3 with the photoassisted electrodeposition method remarkably expediting OER kinetics through an optional pathway of holes utilized by Co species. Ultimately, the CoOOH/FeOOH/F-Fe2O3 photoanode exhibits a satisfactory photocurrent density (3.3-fold higher than pristine alpha-Fe2O3) and a negatively shifted onset potential of 80 mV. This work showcases an appealing maneuver to activate the water oxidation performance of the alpha-Fe2O3 photoanode by an integration strategy of heteroatom doping and cocatalyst coupling.