Facial boron incorporation in hematite photoanode for enhanced photoelectrochemical water oxidation

Abstract Hematite (α-Fe2O3) is a promising photoanode material for light-driven water splitting to make solar fuels. Herein, boron incorporated hematite photoanodes are successfully fabricated by a simple impregnation treatment in borate solution before annealing the iron oxyhydroxide (FeOOH) precursor. X-ray diffraction, Raman and X-ray photoelectron spectroscopies revealed regional enrichment of boron and oxygen vacancy near the outmost surface of the photoanode, forming a unique heterostructure. The boron modified photoanodes exhibited significantly improved photoelectrochemical (PEC) water oxidation efficiency, with up to 37 times enhancement in photocurrent density, approaching 1.12 mA cm−2 at 1.23 VRHE under AM 1.5 G illumination. Electrochemical impedance spectroscopy demonstrated a more favorable hole transfer process in the modified photoanode, which can be ascribed to the surface heterostructure induced build-in electric field, as well as the increase in carrier density introduced by oxygen vacancy.