Constructing Metal–Organic Framework Films with Adjustable Electronic Properties on Hematite Photoanode for Boosting Photogenerated Carrier Transport

Hematite (α-Fe₂O₃) has become a research hotspot in the field of photoelectrochemical water splitting (PEC-WS), but the low photogenerated carrier separation efficiency limits further application. The electronic structure regulation, such as element doping and organic functional groups with different electrical properties, is applied to alleviate the problems of poor electrical conductivity, interface defects, and band mismatch. Herein, α-Fe₂O₃ photoanodes are modified to regulate their electric structures and improve photogenerated carrier transport by the bimetallic metal-organic frameworks (MOFs), which are constructed with Fe/Ni and terephthalate (BDC) with 2-substitution of different organic functional groups (─H, ─Br, ─NO₂ and ─NH₂). The α-Fe₂O₃ photoanode loaded with FeNi-NH₂BDC MOF catalyst exhibits the optimal photocurrent density (2 mA cm^-2) at 1.23 V_RHE, which is 2.33 times that of the pure α-Fe₂O₃ photoanode. The detailed PEC analyses demonstrate that the bimetallic synergistic effect between Fe and Ni can improve the conductivity and inhibit the photogenerated carrier recombination of α-Fe₂O₃ photoanodes. The ─NH₂ group as an electron-donor group can effectively regulate the electron distribution and band structure of α-Fe₂O₃ photoanodes to prolong the lifetime of photogenerated holes, which facilitates photogenerated carrier transport and further enhances the PEC-WS performance of α-Fe₂O₃ photoanode.