Enhancement of the Photoelectrochemical Performance of Core−Shell-Structured Hematite Photoanode with Homojunction Configuration

Abstract

In this study, we designed a core−shell homojunction α-Fe2O3 structure by combining a TiO2 underlayer, regrowth treatment, and selective Zn p-type doping, which generated a strong internal electric field (IEF) to facilitate charge separation. Through the regrowth treatment, a core−shell structure was formed, enabling controlled doping in specific regions to construct the desired junction type. Using this approach, three types of samples were prepared: an undoped sample (H/H), a sample doped with Zn in the shell region (H/H:Zn), and a sample doped with Zn in the core region (H:Zn/H). H/H:Zn exhibited a p−n homojunction, whereas H:Zn/H exhibited an n−p homojunction. These features were investigated using photoelectrochemical (PEC) measurements and time-resolved spectroscopy. In particular, the H/H:Zn with a p−n homojunction demonstrated the best performance by enhancing charge separation and suppressing surface recombination. These results suggest that homojunction design based on the spatial control of dopant distribution enables effective modulation of charge separation characteristics, providing a general approach to improve the PEC performance of α-Fe2O3.