Rational construction of S-doped FeOOH onto FeO nanorods for enhanced water oxidation.

Hematite-based photoanode (α-FeO) is considered the promising candidate for photoelectrochemical (PEC) water splitting due to its relatively small optical bandgap. However, severe charge recombination in the bulk and poor surface water oxidation kinetics have limited the PEC performance of FeO photoelectrodes, which is far below the theoretical value. Herein, a new catalyst, S-doped FeOOH (S-FeOOH), has been immobilized onto the surface of the FeO nanorod (NR) array by a facile chemical bath deposition incorporated thermal sulfuration process. The grown S-FeOOH layer acts not only as an efficient catalyst layer to accelerate the water oxidation on the surface of photoelectrode but also constructs a heterojunction with the light absorption layer to facilitate the interface charge carrier separation and transfer. As expected, the modified S-FeOOH@FeO photoanode achieves a remarkable increase in PEC performance of 2.30 mA cm at 1.23 V versus the reversible hydrogen electrode (V) andan apparent negative shifted onset potential of 250 mV in comparison with pristine FeO (0.95 mA cm at 1.23 V). These results provide a simple and effective strategy to coupling oxygen evolution catalysts with photoanodes for practically high-performance PEC applications.