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 (E_CB ∼ −0.4 eV and E_VB ∼ 0.8 eV) of Sb₂Se₃, match well with Fe₂O₃ (E_CB ∼ 0.29 eV and E_VB ∼ 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.