Enhanced Photoelectrochemical Water Splitting through Synergistic Carrier Separation and Transfer in TiO₂-Ferrihydrite-MXene Nanowire Arrays

The effective separation and efficient transportation of photogenerated carriers within a photoanode are critical factors for achieving outstanding photoelectrochemical (PEC) water splitting. In this study, TiO2-ferrihydrite (Fh)-MXene nanowire arrays (NWAs) are fabricated by a hydrothermal method followed by spin coating. TiO2-Fh-MXene NWAs achieved a photocurrent density of 1.44 mA/cm2 at 1.23 V versus the reversible hydrogen electrode (vs RHE), surpassing TiO2-Fh by 2.05 times and TiO2 by 2.93 times. According to the electrochemical impedance spectroscopy, photoluminescence, and Mott–Schottky measurements, the significant enhancement in the separation of photogenerated electron–hole pairs and efficient carrier transportation are ascribed to the integration of Fh and MXene, respectively. Additionally, the light absorption of TiO2 NWAs is improved with the incorporation of the Fh-MXene layer. This work provides valuable insights into the fabrication of photoanodes, especially using wide bandgap materials.