Surface passivation of undoped hematite nanorod arrays via aqueous solution growth for improved photoelectrochemical water splitting

A facile solution-based strategy was found to be effective for surface passivation of undoped hematite nanorod photoanodes by adding noble-metal chlorides such as HAuCl₄ and H₂PtCl₆ in the Fe³⁺ precursor solution. XPS and Raman spectra revealed that noble-metal ions would not be doped into, but lead to surface disorder of hematite. Incident photon to current efficiency (IPCE) of the hematite photoanode grown in HAuCl₄ and H₂PtCl₆ contained precursor solution was increased from 3.6% to 11.5% and 12.9%, respectively, at 365nm and 1.23V vs. RHE (reversible hydrogen electrode). This photoelectrochemical (PEC) enhancement was ascribed to the surface passivation, which resulted in a reduced recombination of photogenerated carriers, as confirmed by ultrafast transient absorption spectroscopy.