Surface Rh-Boosted Photoelectrochemical Water Oxidation of a-Fe2O3 by Reduced Overpotential in the Rate-Determining Step

Abstract

The photoelectrochemical behavior of Rh cluster-deposited hematite (a-Fe2O3) photoanodes (a-Fe2O3@Rh) was investigated. The interactions between Rh clusters and a-Fe2O3 nanorods were elucidated both experimentally and computationally. A facile UV-assisted solution casting deposition method allowed the deposition of 2 nm Rh clusters on a-Fe2O3. The deposited Rh clusters effectively enhanced the photoelectrochemical performance of the a-Fe2O3 photoanode, and electrochemical impedance spectroscopy (EIS) and Mott-Schottky analysis were applied to understand the working mechanism for the a-Fe2O3@Rh photoanodes. The results revealed a distinctive carrier transport mechanism for a-Fe2O3@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 a-Fe2O3 and a-Fe2O3@Rh nanorods. Owing to enhanced carrier generation and hole transfer, the optimum a-Fe2O3@Rh3 sample showed 78% increased photocurrent density, reaching 1.12 mA/cm(-2) at 1.23 V-RHE compared to that of the pristine a-Fe2O3 nanorods electrode.