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|cat) and cocatalyst–electrolyte (cat|ele) interface. In our work, we used ferrihydrite (Fh)-modified Ti–Fe 2 O 3 as a model to explore the transfer process of photogenerated charge carriers between the Ti–Fe 2 O 3 –Fh (Ti–Fe 2 O 3 |Fh) interface and Fh-electrolyte (Fh|ele) interface. The results demonstrate that the biphasic structure (Fh/Ti–Fe 2 O 3 ) possesses the advantage that the minority hole transfer from Ti–Fe 2 O 3 to Fh is driven by the interfacial electric field at the Ti–Fe 2 O 3 |Fh interface; meanwhile, the holes reached at the surface of Fh can rapidly inject into the electrolyte across the Fh|ele interface. As a benefit from the improved charge transfer at the Ti–Fe 2 O 3 |Fh and Fh|ele interface, the photocurrent density obtained by Fh/Ti–Fe 2 O 3 can reach 2.32 mA cm −2 at 1.23 V versus RHE, which is three times higher than that of Ti–Fe 2 O 3 . Graphical Water splitting : The excellent performance of ferrihydrite (Fh)/Ti–Fe 2 O 3 is attributed to the unhindered charge transfer at the Ti–Fe 2 O 3 |Fh and Fh|electrolyte interfaces. As a benefit from this improved charge transfer, the photocurrent density obtained by Fh/Ti–Fe 2 O 3 can reach 2.32 mA cm −2 at 1.23 V versus the reversible hydrogen electrode, which is three times higher than that of Ti–Fe 2 O 3 .