Conductive MOFs coating on hematite photoanode for activity boost via surface state regulation

The ability of hematite (α-Fe2O3) for photoelectrochemical water oxidation is limited by its poor conductivity. The construction of core-shell photoanode with a cocatalyst overlayer of metal-organic frameworks (MOFs) has been recognized as an effective method to enhance activity and stability. However, most MOFs cocatalysts are insulators, charge conductivity of MOFs and surface state of α-Fe2O3 synchronously modulation are needed for efficient carrier migration. In this study, a conductive MOFs (cMOFs) overlayer based on 2,5-dihydroxybenzoquinone was conformally coated on Ti:Fe2O3 using caffeic acid as coordination agent. The catechol groups in caffeic acid not only bridges Ti:Fe2O3 with cMOFs, but also regulates the surface state of Ti:Fe2O3. Coordination of catechol with Ti:Fe2O3 results in shortening of Fe–O bond and generation of surface state of high energy, thereby increasing its capacity for holes storage. The synthesized Ti:Fe2O3@CoFe-cMOFs exhibits outstanding photocurrent density of 3.3 mA cm−2 with high stability.