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

Abstract

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 V_RHE, 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.