Direct Z scheme-fashioned photoanode systems consisting of Fe₂O₃ nanorod arrays and underlying thin Sb₂Se₃ layers toward enhanced photoelectrochemical water splitting performance

Abstract

An elegant Z-scheme-fashioned photoanode consisting of Fe2O3 nanorod arrays and underlying thin Sb2Se3 layers was rationally constructed. The photocurrent density of the Sb2Se3-Fe2O3 Z-scheme photoanode reached 3.07 mA cm-2 at 1.23 V vs. RHE, three times higher than that of pristine Fe2O3 at 1.03 mA cm-2. An obvious cathodic shift of the photocurrent onset potential of about 200 mV was also observed. The transient photovoltage response demonstrates that the suitable band edges (ECB ∼ -0.4 eV and EVB ∼ 0.8 eV) of Sb2Se3, match well with Fe2O3 (ECB ∼ 0.29 eV and EVB ∼ 2.65 eV), permitting the photoexcited electrons on the conduction band of the Fe2O3 to transfer to the valence band of Sb2Se3, and recombine with the holes therein, thus allowing a high concentration of holes to collect in the Fe2O3 for water oxidation. The transient absorption spectra further corroborate that the built-in electric field in the p-n heterojunction leads to a more effective separation and a longer lifetime of the charge carriers.