Achieving surface-sealing of hematite nanoarray photoanode with controllable metal–organic frameworks shell for enhanced photoelectrochemical water oxidation

Abstract

Surface engineering of hematite (α-Fe2O3) photoanode by coupling electrocatalytically active metal–organic frameworks (MOFs) is an efficient way of boosting surface charge transfer for photoelectrochemical (PEC) water oxidation. However, the precise and controllable coating of conformal MOFs overlayer through a facile approach on photoelectrode still faces a challenge. In this work, NiFe metal–organic frameworks (NiFe-MOFs) are conformally deposited on zirconium-doped hematite (Zr-Fe2O3) by a novel indirect ligand-assisted transformation method, in which the well-coupled NiFe-layered double hydroxides (NiFe-LDHs) on photoanode act as self-templates due to their special layered structure and suitable interlayer spacing to provide with large specific area for the in-situ etching and coordinating, thus achieving the in-situ transformation of NiFe-LDHs layer into conformal NiFe-MOFs shell. Then, detailed investigations reveal that this conformal NiFe-MOFs shell endows the photoanode with a larger electrochemical active area, higher stability, and longer charge carrier lifetime compared to that of crystalline NiFe-MOFs on Zr-Fe2O3 from traditional solvothermal, resulting in outstanding PEC water oxidation performance of the target core–shell Zr-Fe2O3@NiFe-MOFs photoanode.