In-situ coating of multifunctional FeCo-bimetal organic framework nanolayers on hematite photoanode for superior oxygen evolution

The well-designed FeCo-MOF/Fe 2 O 3 compound photoanode displays favorable PEC performances, which can be attributed to the coating of multifunctional FeCo MOF nanolayer that passivate the surface states, construct the p-n heterojunction and improve the water oxidation kinetics, all of these enable the substantially promoted charge separation and transport. • Ultrathin FeCo MOF nanolayers coated on Fe 2 O 3 photoanode are in-situ formed. • Multifunctional roles of FeCo MOF on Fe 2 O 3 is disclosed. • This design endows photoanode with boosted charge separation/injection efficiency. • The catalytic mechanism for PEC water oxidation is unravelled. Owing to the high theoretical photocurrent density, the hematite ( α -Fe 2 O 3 ) based photoanode has been intensively concerned in photoelectrochemical (PEC) water splitting, but its serious charge recombination and sluggish water oxidation kinetics are still the stumbling blocks. This work reports a high-performance Fe 2 O 3 -based photoanode achieved by coating multifunctional FeCo-bimetal organic framework (MOF) nanolayers (NLs) on Fe 2 O 3 nanoarrays via an in-situ solvothermal process. The FeCo MOF NLs introduced not only effectively passivate the surface states of Fe 2 O 3 photoanode and boost the water oxidation kinetics serving as the cocatalyst, but also construct p-n heterojunctions with Fe 2 O 3 to accelerate the directional migration and separation of photogenerated charge carriers. Expectedly, the as-obtained FeCo-MOF/Fe 2 O 3 photoanode exhibits an apparent negative shift of onset potential, an excellent long-term PEC stability, and highly improved photocurrent density. This finding provides a novel and effective strategy to introduce advanced multifunctional surface coating for enhancing the PEC performance of photoelectrodes.