Surface Rh-Boosted Photoelectrochemical Water Oxidation of α-Fe 2 O 3 by Reduced Overpotential in the Rate-Determining Step.

The photoelectrochemical behavior of Rh cluster-deposited hematite (α-Fe ₂ O ₃ ) photoanodes (α-Fe ₂ O ₃ @Rh) was investigated. The interactions between Rh clusters and α-Fe ₂ O ₃ nanorods were elucidated both experimentally and computationally. A facile UV-assisted solution casting deposition method allowed the deposition of 2 nm Rh clusters on α-Fe ₂ O ₃ . The deposited Rh clusters effectively enhanced the photoelectrochemical performance of the α-Fe ₂ O ₃ photoanode, and electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis were applied to understand the working mechanism for the α-Fe ₂ O ₃ @Rh photoanodes. The results revealed a distinctive carrier transport mechanism for α-Fe ₂ O ₃ @Rh and increased carrier density, while the absorbance spectra remained unchanged. Furthermore, density functional theory (DFT) calculations of the oxygen evolution reaction (OER) mechanism corresponded well with the experimental results, indicating a reduced overpotential of the rate-determining step. In addition, DFT calculation models based on the X-ray diffraction (XRD) measurements and X-ray photoelectron spectroscopy (XPS) results provided precise water-splitting mechanisms for the fabricated α-Fe ₂ O ₃ and α-Fe ₂ O ₃ @Rh nanorods. Owing to enhanced carrier generation and hole transfer, the optimum α-Fe ₂ O ₃ @Rh3 sample showed 78% increased photocurrent density, reaching 1.12 mA/cm ^-2 at 1.23 V _RHE compared to that of the pristine α-Fe ₂ O ₃ nanorods electrode.