Accelerating Oxygen Evolution Reaction Kinetics by Reconstructing Layered and Defective Ni3FeOOH/FeOOH in a Hematite Photoanode

Abstract

Surface engineering has outstanding advantages for improving the carrier exaction of photoelectrodes in the photoelectrochemical water splitting field. NiFe‐layered double hydroxides (NiFe‐LDH), as promising catalysts for water oxidation, can facilitate carrier transport. But surface collapse and structural deformation limit their applications. In this work, a hematite (α‐Fe2O3) photoanode is sequentially cumulatively modified with NiFe‐LDH (Ni3FeOOH), Ag/SiO2, and FeOOH, and exhibits a high photocurrent density, which increases from 0.92 to 4.54 mA cm−2 at 1.23 V relative to the standard hydrogen electrode (VRHE). The mechanism studies demonstrate that the introduction of FeOOH suppresses the electrochemical self‐reduction of Ni3FeOOH, remedies the obvious valley formed in the current density and voltage curve, reduces recombination, and facilitates the OH− transformation, which increases the catalytic activities of the photoanode. The Ag@SiO2 nanoparticles can reduce the interface defects between Ni3FeOOH and FeOOH. The density‐functional theory calculation reveals that the valley is caused by the direction of the internal electric field formed between Ni3FeOOH and α‐Fe2O3, which is opposite to that of solid–liquid junction, resulting in serious carrier recombination. FeOOH possesses a higher electrostatic potential than that of Ni3FeOOH and α‐Fe2O3 and forms an internal electric field directing from α‐Fe2O3/Ni3FeOOH to FeOOH, which synergistically promotes carrier separation with solid–liquid junction.