Facile synthesis of an ultrathin ZIF-67 layer on the surface of Sn/Ti co-doped hematite for efficient photoelectrochemical water oxidation

Hematite is a promising photoanode for photoelectrochemical (PEC) water splitting but its practical performance has been severely hindered by its poor conductivity and sluggish water oxidation kinetics. Metal-organic frameworks (MOFs), considered as efficient oxygen evolution catalysts (OECs), have been widely applied for PEC water splitting in recent years. Here, we modified an ultrathin (about 2 nm) Co-based ZIF-67 layer on the surface of Sn/Ti co-doped α-Fe2O3 by a simple one-step solvothermal method. The resulting photoanode achieved a photocurrent density of 2 mA cm-2 at 1.23 VRHE, which was four-fold that of pristine Fe2O3. Detailed investigations manifest that Sn and Ti co-doping improves the conductivity of hematite, while ZIF-67 coating not only expands the optical-response range, but also accelerates the charge transfer at the semiconductor-electrolyte (S-E) interface to facilitate water oxidation kinetics. This work provides a method to design and study MOF overlayer decorating hematite photoanodes towards improving the PEC performance.