Ferrihydrite-Modified Ti-Fe2O3 as an Effective Photoanode: The Role of Interface Interactions in Enhancing the Photocatalytic Activity of Water Oxidation

Semiconductor electrodes integrated with cocatalysts are key components of photoelectrochemistry (PEC)-based solar-energy conversion. However, efforts to optimize the PEC device have been limited by an inadequate understanding of the interface interactions between the semiconductor-cocatalyst (sem vertical bar cat) and cocatalyst-electrolyte (cat vertical bar ele) interface. In our work, we used ferrihydrite (Fh)-modified Ti-Fe2O3 as a model to explore the transfer process of photogenerated charge carriers between the Ti-Fe2O3-Fh (Ti-Fe2O3 vertical bar Fh) interface and Fh-electrolyte (Fh vertical bar ele) interface. The results demonstrate that the biphasic structure (Fh/Ti-Fe2O3) possesses the advantage that the minority hole transfer from Ti-Fe2O3 to Fh is driven by the interfacial electric field at the Ti-Fe2O3 vertical bar Fh interface; meanwhile, the holes reached at the surface of Fh can rapidly inject into the electrolyte across the Fh vertical bar ele interface. As a benefit from the improved charge transfer at the Ti-Fe2O3 vertical bar Fh and Fh vertical bar ele interface, the photocurrent density obtained by Fh/Ti-Fe2O3 can reach 2.32 mA cm(-2) at 1.23 V versus RHE, which is three times higher than that of Ti-Fe2O3.